Afferent projections to the rat nuclei raphe magnus, raphe pallidus and reticularis gigantocellularis pars α demonstrated by iontophoretic application of choleratoxin (subunit b)

The aim of the present study was to identify the specific afferent projections to the rostral and caudal nucleus raphe magnus, the gigantocellular reticular nucleus pars α and the rostral nucleus raphe pallidus. For this purpose, small iontophoretic injections of the sensitive retrograde tracer choleratoxin (subunit b) were made in each of these structures. In agreement with previous retrograde studies, after all injection sites, a substantial to large number of labeled neurons were observed in the dorsal hypothalamic area and dorsolateral and ventrolateral parts of the periaqueductal gray, and a small to moderate number were found in the lateral preoptic area, bed nucleus of the stria terminalis, paraventricular hypothalamic nucleus, central nucleus of the amygdala, lateral hypothalamic area, parafascicular area, parabrachial nuclei, subcoeruleus area and parvocellular reticular nucleus. In addition, depending on the nucleus injected, we observed a variable number of retrogradely labeled cells in other regions. After injections in the rostral nucleus raphe magnus, a large number of labeled cells were seen in the prelimbic, infralimbic, medial and lateral precentral cortices and the dorsal part of the periaqueductal gray. In contrast, after injections in the other nuclei, fewer cells were localized in these structures. Following raphe pallidus injections, a substantial to large number of labeled cells were observed in the medial preoptic area, median preoptic nucleus, ventromedial part of the periaqueductal gray, Kölliker-Fuse and lateral paragigantocellular reticular nuclei. Following injections in the other areas, a small to moderate number of cells appeared. After gigantocellular reticular pars α injections, a very large and substantial number of labeled neurons were found in the deep mesencephalic reticular formation and oral pontine reticular nucleus, respectively. After the other injections, fewer cells were seen. Following rostral raphe magnus or raphe pallidus injections, a substantial number of labeled cells were observed in the insular and perirhinal cortices. Following caudal raphe magnus or gigantocellular reticular pars α injections, fewer cells were found. After raphe magnus or gigantocellular reticular pars α injections, a moderate to substantial number of cells were localized in the fields of Forel, lateral habenular nucleus and ventral caudal pontine reticular nucleus. Following raphe pallidus injections, only a small number of cells were seen. Our data indicate that the rostral and caudal parts of the nucleus raphe magnus, the gigantocellular reticular nucleus pars α and the nucleus raphe pallidus receive afferents of comparable strength from a large number of structures. In addition, a number of other afferents give rise to stronger inputs to one or two of the four nuclei studied. Such differential inputs might be directed to populations of neurons with different physiological roles previously recorded specifically in these nuclei.     

The organization of preoptic-medullary circuits in the male rat: evidence for interconnectivity of neural structures involved in reproductive behavior, antinociception and cardiovascular regulation.

The present studies used anatomical tract-tracing techniques to delineate the organization of pathways linking the medial preoptic area and the ventral medulla, two key regions involved in neuroendocrine, autonomic and sensory regulation. Wheatgerm agglutinin-horseradish peroxidase injections into the ventromedial medulla retrogradely labeled a large number of neurons in the medial preoptic area, including both the median and medial preoptic nuclei. The termination pattern of preoptic projections to the medulla was mapped using the anterograde tracers Phaseolus vulgaris leucoagglutinin and biotinylated dextran amine. Tracer injections into the preoptic area produced a dense plexus of labeled fibers and terminals in the ventromedial and ventrolateral pons and medulla. Within the caudal pons/rostral medulla, medial preoptic projections terminated heavily in the nucleus raphe magnus; strong anterograde labeling was also present in the pontine reticular field. At mid-medullary levels, labeled fibers focally targeted the nucleus paragigantocellularis, in addition to the heavy fiber labeling present in the midline raphe nuclei. By contrast, very little labeling was observed in the caudal third of the medulla. Experiments were also conducted to map the distribution of ventral pontine and medullary neurons that project to the medial preoptic area. Wheatgerm agglutinin-horseradish peroxidase injections in the preoptic area retrogradely labeled a significant population of neurons in the ventromedial and ventrolateral medulla. Ascending projections from the medulla to the preoptic area were organized along rostral-caudal, medial-lateral gradients. In the caudal pons/rostral medulla, retrogradely labeled cells were aggregated along the midline raphe nuclei; no retrograde labeling was present laterally at this level. By contrast, in the caudal half of the medulla, cells retrogradely labeled from the medial preoptic area were concentrated as a discrete zone dorsal to the lateral reticular nucleus; labeled cells were not present in the ventromedial medulla at this level. The present findings suggest that the medial preoptic area and ventral midline raphe nuclei share reciprocal connections that are organized in a highly symmetrical fashion. By contrast, preoptic-lateral medullary pathways are not reciprocal. These preoptic-brainstem circuits may participate in antinociceptive, autonomic and reproductive behaviors.     

Brain stem afferents to the periabducens reticular formations (PARF) in the cat

Summary Six injections of HRP were placed in the periabducens reticular formation (PARF). Two were placed ventromedial to the caudal half of the abducend nucleus (VIn), two were placed further laterally and ventral to the rostral half of the nucleus, and two were placed rostral to the nucleus. Most injections in PARF produced cell labeling in the vestibular and perihypoglossal nuclei bilaterally and labeled cells in the reticularis gigantocellularis (Rgc) and reticularis pontis caudalis (Rpc) nuclei contralateral to the injection site. Few labeled neurons were found in the caudal part of the paramedian pontine reticular formation (PPRF). In the mesencephalon, bilateral but more numerous ipsilateral labeled cells were found in the medial mesodiencephalic region including the nuclei of Cajal, Darkschewitsch and the posterior commissure. Injections placed caudomedial to VIn resulted in a characteristic concentration of labeled cells in the ipsilateral nucleus cuneiformis and rostral half of the contralateral superior colliculus (SC). Injections placed rostral to VIn in PARF produced cell labeling in the nucleus campi Foreli. The results are related to physiological evidence which suggests that PARF is an important premotor center for coordination of oculomotor, head and body movements.     

The afferent connections of the inferior olivary complex in rats: A study using the retrograde transport of horseradish peroxidase

Retrograde transport of horseradish peroxidase (HRP) was used to define the origin of afferents to the inferior olivary complex (IOC) in rats. Using both ventral and dorsal surgical approaches to the brainstem, HRP was injected into the IOC through a micropipette affixed to the tip of a 1-μl Hamilton syringe. After a 2-day postoperative survival, animals were sacrificed by transcardiac perfusion with a 1% paraformaldehyde-1.25% gluteraldehyde solution, and brains were processed according to the DeOlmos protocol (1977), using o-dianisidine as the chromogen. Labeled cells were found at many levels of the nervous system extending from lumbar spinal cord to cerebral cortex. This wide-ranging input from numerous regions clearly underscores the complexity of the IOC and its apparent involvement in several functions. Within the spinal cord, labeled neurons were identified from cervical to lumbar but not at sacral levels. These neurons were found contralaterally in the neck region of the dorsal horn and in the medial portions of the intermediate gray. In the caudal brainstem, reactive cells in the dorsal column nuclei, the spinal trigeminal nucleus, and the subnucleus y of the vestibular complex were observed primarily contralateral to the injection sites. Labeling within the gigantocellular, magnocellular, ventral, and lateral reticular nuclei and the nucleus prepositus hypoglossi was primarily ipsilateral. Reactive neurons in the medial and inferior vestibular nuclei were predominantly ipsilateral or contralateral to HRP injections into the caudal or rostral IOC, respectively. The dentate and interposed nuclei of the cerebellum contained small, lightly labeled neurons primarily contralateral to the injection site, while the fastigial nuclei contained a few relatively large, heavily labeled cells bilateral to caudal olivary injections. Ipsilaterally labeled mesencephalic regions included the periaqueductal gray, interstitial nucleus of Cajal, rostromedial red nucleus, ventral tegmental area, medial terminal nucleus of the accessory optic tract, nucleus of the optic tract, and the lateral deep mesencephalic nucleus. The caudal part of the pretectum and small cells of the stratum profundum of the superior colliculus were labeled predominantly contralateral to the injection. In the caudal diencephalon labeled neurons were most numerous within the nucleus of Darkschewitsch and the subparafascicular nucleus, primarily ipsilateral to olivary injections. Scattered reactive neurons were also found within the ipsilateral zone incerta. With the exception of the zona incerta, all labeled mesencephalic and diencephalic nuclei had some bilateral representation of labeled cells. No labeled neurons were identified within the basal ganglia, while numerous reactive cells were found bilaterally within layer V of the frontal and parietal cerebral cortex.     

The fiber projections from the dentate nucleus to the reticular formation of the brain stem in the rabbit

Summary The projections from the dentate nucleus to the reticular formation of the brain stem in rabbit have been examined by means of the Fink-Heimer technique. The fibers arising from the dentate nucleus primarily project to the reticular formation via the contralateral and ipsilateral descending limbs of the brachium conjunctivum. The descending fibers project bilaterally to the parvocellular reticular nucleus, the ventral reticular nucleus, the gigantocellular reticular nucleus, the nucleus raphe magnus, the oral and caudal pontine reticular nuclei, and the reticulo-tegmental nucleus.     

Cerebellar afferent projections from the vestibular nuclei in the cat: An experimental study with the method of retrograde axonal transport of horseradish peroxidase

Summary Details of cerebellar afferent projections from the vestibular nuclei were investigated by the method of retrograde axonal transport of horseradish peroxidase (HRP) in the cat. The distribution of labeled cells in the vestibular nuclei following HRP injections in various parts of the cerebellum indicates that vestibular neurons in the medial and descending nuclei and cell groups f and x project bilaterally to the entire cerebellar vermis, the flocculus, the fastigial nucleus and the anterior and posterior interpositus nuclei. In addition, labeled cells (giant, medium and small) were consistently found bilaterally in the superior and lateral vestibular nuclei following HRP injections in the nodulus, flocculus, fastigial nucleus, and following large injections in the vermis. No labeled cells were observed in cases of HRP injections in crus I and II, the paramedian lobule, paraflocculus and lateral cerebellar nuclei. The present findings indicate that secondary vestibulocerebellar fibers project to larger areas in the cerebellum and originate from more subdivisions and cell groups of the vestibular nuclear complex than previously known.List of Abbreviations B.c. superior cerebellar peduncle (brachium conjunctivum) - D descending (inferior) vestibular nucleus - f cell group f in descending vestibular nucleus - g group rich in glia cells, caudal to the medial vestibular nucleus - HIX hemispheral lobule IX - HVIIA cr. Ia, p; cr. IIa, p anterior and posterior folia of crus I and II of the ansiform lobule - HVIIB, HVIIIA, B sublobules A and B of hemispheral lobules VII and VIII - i.c. nucleus intercalatus (Staderini) - L lateral vestibular nucleus (Deiters) - l small-celled lateral group of lateral vestibular nucleus - M medial (triangular or dorsal) vestibular nucleus - N. cu. e. accessory cuneate nucleus - N. f. c. cuneate nucleus - N. mes. V mesencephalic nucleus of trigeminal nerve - N.tr. s. nucleus of solitary tract - N. VII facial nerve - pfl. d. dorsal paraflocculus - pfl. v. ventral paraflocculus - S superior vestibular nucleus (Bechterew) - Sv. cell group probably representing the nucleus supravestibularis - Tr. s. solitary tract - x small-celled group x, lateral to the descending vestibular nucleus - y small-celled groupy, lateral to the lateral vestibular nucleus (Deiters) - z cell group dorsal to the caudal part of the descending vestibular nucleus - I–VI vermian lobules I–VI - V, VI, XII cranial motor nerve nuclei - VIIA, B; VIIIA, B anterior and posterior sublobules of lobules VII and VIII - IX uvula - X nodulus; dorsal motor nucleus of vagus nerve On leave from the Laboratory of Neurobiology and Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand, under the Felllowship Program of the Norwegian Agency for International Development (NORAD)     

Reticulospinal neurons in the pontomedullary reticular formation of the monkey (Macaca fascicularis)

Recent neurophysiological studies indicate a role for reticulospinal neurons of the pontomedullary reticular formation (PMRF) in motor preparation and goal-directed reaching in the monkey. Although the macaque monkey is an important model for such investigations, little is known regarding the organization of the PMRF in the monkey. In the present study, we investigated the distribution of reticulospinal neurons in the macaque. Bilateral injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) were made into the cervical spinal cord. A wide band of retrogradely labeled cells was found in the gigantocellular reticular nucleus (Gi) and labeled cells continued rostrally into the caudal pontine reticular nucleus (PnC) and into the oral pontine reticular nucleus (PnO). Additional retrograde tracing studies following unilateral cervical spinal cord injections of cholera toxin subunit B revealed that there were more ipsilateral (60%) than contralateral (40%) projecting cells in Gi, while an approximately 50:50 ratio contralateral to ipsilateral split was found in PnC and more contralateral projections arose from PnO. Reticulospinal neurons in PMRF ranged widely in size from over 50 μm to under 25 μm across the major somatic axis. Labeled giant cells (soma diameters greater than 50 μm) comprised a small percentage of the neurons and were found in Gi, PnC and PnO. The present results define the origins of the reticulospinal system in the monkey and provide an important foundation for future investigations of the anatomy and physiology of this system in primates.     

Collateralization of cerebellar efferent projections to the paraoculomotor region,superior colliculus,and medial pontine reticular formation in the rat: a fluorescent double-labeling study

Summary Collateralization of cerebellar efferent projections to the oculomotor region, superior colliculus (SC), and medial pontine reticular formation (mPRF) was studied in rats using fluorescent tracer substances. In one group, True Blue (TB) was injected into the oculomotor complex (OMC), including certain paraoculomotor nuclei and supraoculomotor ventral periaqueductal gray (PAG), and Diamidino Yellow (DY) was injected into the medial pontine reticular formation (mPRF) or pontine raphe. The largest number of single-TB-labeled (paraoculomotor-projecting) cells was observed in the medial cerebellar nucleus (MCN) and posterior interposed nucleus (PIN), whereas the largest number of single-DY-labeled (mPRF-projecting) cells was in the MCN. Double-TB/DY-labeled cells were present in the caudal two-thirds of the MCN, suggesting that some MCN neurons send divergent axon collaterals to the paraoculomotor region and mPRF. In another group, TB was injected into the SC and DY into the mPRF. The largest number of single-TB-labeled (SC-projecting) cells was in the PIN, although a considerable number of cells was observed in the caudal MCN, and ventral lateral cerebellar nucleus (LCN). Single-DY-labeled (mPRF-projecting) neurons were primarily located in the central and ventral MCN, but were also present in the lateral anterior interposed (AIN) and in the LCN. Double-TB/DY-labeled neurons were observed in the caudal two-thirds of the MCN and in the central portion of the LCN. The most significant new findings of the study concerned the MCN, which not only contained neurons that projected independently to the paraoculomotor region, SC, and mPRF, but also contained a considerable number of cells which collateralized to project to more than one of these nuclei. The possibility that the MCN projects to the supraoculomotor ventral PAG (containing an oculomotor interneuron system) and to the mPRF, which in the cat and monkey contain neural elements essential to the production of saccadic eye movements, is discussed. The anatomical findings suggest that the MCN in the rat plays an important role in eye movement.Abbreviations AI anterior interposed nucleus - AIN anterior interposed nucleus - BC brachium conjunctivum (sup. cerebellar peduncle) - dlh dorsolateral hump of the AI - dmc dorsomedial crest of the AI - IC inferior colliculus - ICP inferior cerebellar peduncle - Inf infracerebellar nucleus - L lateral cerebellar (dentate) nucleus - LCN lateral cerebellar (dentate) nucleus - M medial cerebellar (fastigial) nucleus - MCN medial cerebellar (fastigial) nucleus - MLF medial longitudinal fasciculus - mPRF medial pontine reticular formation (incl. nuc. reticularis pontis oralis and caudalis) - OMC oculomotor complex - OMN oculomotor nucleus - PI posterior interposed nucleus - PIN posterior interposed nucleus - RN red nucleus - SC superior colliculus - Vl lateral vestibular nucleus - Vs superior vestibular nucleus - Y cell group Y     

Afferents of the caudal fastigial nucleus in a New World monkey (Cebus apella)

Summary The afferents of the fastigial nucleus (FN) were studied in two capuchin monkeys (Cebus apella) one of which had received a unilateral injection of horseradish peroxidase in the caudal FN, and a second monkey which received a control injection that involved the lateral caudal FN but extended into the cerebellar white matter between the FN and posterior interposed nucleus (PIN). All of the sources of FN afferents were found to be labeled bilaterally. In addition to the restricted distribution of labeled Purkinje cells in lobules VI and VII of the posterior lobe vermis (oculomotor vermis), retrogradely labeled cells were present in the dorsolateral pontine nucleus (DLPN), dorsomedial pontine nucleus (DMPN), nucleus reticularis tegmenti pontis (NRTP), pontine raphe (PR), paramedian nucleus reticularis pontis caudalis (NRPC), nucleus prepositus hypoglossi (NPH), subnucleus b of the medial accessory olivary nucleus (sbMAO), and vestibular complex (VC). The second (control) injection appeared to confirm a proposed (Langer et al. 1985b) projection from the flocculus to the basal interstitial nucleus. The results are discussed in terms of the functional relationships of the FN to the frontal eye field and oculomotor-related brainstem structures involved in the production of saccadic and smooth pursuit eye movements.Abbreviations AIN anterior interposed nucleus, cerebellum - BC brachium conjunctivum (sup. cerebellar peduncle) - BIN basal interstitial nucleus, cerebellum - BPN basilar pontine nuclei - CS corticospinal (pyramidal) tract - DBC decussation of brachium conjunctivum - DLPN dorsolateral pontine nucleus (Nyby and Jansen 1951) - DMPN dorsolateral pontine nucleus - DN dentate nucleus, cerebellum - DNV descending nucleus of the trigeminal complex (C.N. V) - FN fastigial nucleus, cerebellum - IC inferior colliculus - ICP inferior cerebellar peduncle - IVN inferior vestibular nucleus - LCN lateral (external) cuneate nucleus - LPN lateral pontine nucleus - MAO medial accessory nucleus of the inferior olivary complex - ML medial lemniscus - MLF medial longitudinal fasciculus - MRF medullary reticular formation (nuc. retic. gigantocellularis) - MVN medial vestibular nucleus - NI nucleus intercalatus of Staderini of the perihypoglossal complex - NPH nucleus prepositus hypoglossi - NRPC nucleus reticularis pontis caudalis - NRPO nucleus reticularis pontis oralis - NRTP nucleus reticularis tegmenti pontis - PIN posterior interposed nucleus - PR pontine raphe - sbMAO subnucleus b, medial accessory olivary nucleus - SC superior colliculus - sbPVG supragenial peri- (IVth) ventricular gray - SVN superior vestibular nucleus - VIn abducens nerve (C.N. VI) - XIIn hypoglossal nerve (C.N. XII)     

Retrograde labeling of neurons in the brain stem following injections of [3H]choline into the forebrain of the rat

Summary In an attempt to identify cholinergic neurons of the brain stem which project to the forebrain, retrograde labeling of neurons in the brain stem was examined by autoradiography following injections of 20 Ci [³H]choline into the thalamus, hypothalamus, basal forebrain and frontal cortex. After injections into the thalamus, retrogradely labeled neurons were evident within the lateral caudal mesencephalic and dorsolateral oral pontine tegmentum (particularly in the laterodorsal and pedunculopontine tegmental nuclei) and in smaller number within the latero-medial caudal pontine (Reticularis pontis caudalis, Rpc) and medullary (Reticularis gigantocellularis, Rgc) reticular formation. Following [³H]choline injections into the lateral hypothalamus and into the basal forebrain, retrogradely labeled neurons were localized in the dorsolateral caudal midbrain and oral pontine tegmentum and in smaller number in the medial medullary reticular formation (Rgc), as well as in the midbrain, pontine and medullary raphe nuclei. After injections into the anterior medial frontal cortex, a small number of retrogradely labeled cells were found in the brain stem within the laterodorsal tegmental nucleus and the dorsal raphe nucleus. In a parallel immunohistochemical study, choline acetyltransferase (ChAT)-positive neurons were found to be located in most of the regions of the reticular formation where cells were retrogradely labeled from the forebrain following [³H]choline injections. These results suggest that multiple cholinergic neurons within the lateral caudal midbrain and dorsolateral oral pontine tegmentum and a few within the caudal pontine and medullary reticular formation project to the thalamus, hypothalamus and basal forebrain and that a limited number of pontine cholinergic neurons project to the frontal cortex.Abbreviations of Neuroanatomical Terms 3 oculomotor nuc - 4 trochlear nuc - 4V fourth ventricle - 6 abducens nuc - 7 facial nuc - 7n facial nerve - 8n vestibulocochlear nerve - 10 dorsal motor nuc vagus - 12 hypoglossal nuc - 12n hypoglossal nerve - Amb ambiguus nuc - Aq cerebral aqueduct - bic brachium inf colliculus - CB cerebellum - CG central gray - CLi caudal linear nuc raphe - Cnf cuneiform nuc - cp cerebral peduncle - Cu cuneate nuc - D nuc Darkschewitsch - DCo dorsal cochlear nuc - DLL dorsal nuc lateral lemniscus - DPB dorsal parabrachial nuc - DR dorsal raphe nuc - dsc dorsal spinocerebellar tract - DTg dorsal tegmental nuc - dtgx dorsal tegmental decussation - ECu external cuneate nuc - Fl flocculus - IC inferior colliculus - icp inferior cerebellar peduncle - IF interfascicular nuc - InC interstitial nuc Cajal - IO inferior olive - IP interpeduncular nuc - KF Kolliker-Fuse nuc - LC locus coeruleus - Ldt laterodorsal tegmental nuc - Ifp longitudinal fasciculus pons - ll lateral lemniscus - LRt lateral reticular nuc - LRtS5 lateral reticular nucsubtrigeminal - LSO lateral superior olive - LTz lateral nuctrapezoid body - LVe lateral vestibular nuc - mcp middle cerebellar peduncle - Me5 mesencephalic trigeminal nuc - MGD medial geniculate nuc, dorsal - ml medial lemniscus - mlf medial longitudinal fasciculus - MnR median raphe nuc - Mo5 motor trigeminal nuc - MSO medial superior olive - MTz medial nuc trapezoid bbody - MVe medial vestibular nuc - PBg parabigeminal nuc - Pgl nuc paragigantocellularis lateralis - Pn pontine nuc - PPTg pedunculopontine tegmental nuc - Pr5 principal sensory trigeminal - PrH prepositive hypoglossal nuc - py pyramidal tract - Rgc reticularis gigantocellularis - Rgca reticularis gigantocellularis pars alpha - Rmes reticularis mesencephali - RMg raphe magnus nuc - RN red nuc - Ro nuc Roller - ROb raphe obscurus nuc - Rp reticularis parvicellularis - RPa raphe pallidus nuc - Rpc reticularis ponds caudalis - RPn raphe pontis nuc - Rpo reticularis pontis oralis - RR retrorubral nuc - rs rubrospinal tract - RtTg reticulotegmental nuc pons - s5 sensory root trigeminal nerve - SC superior colliculus - SCD superior colliculus,deep layer - SCI superior colliculus, intermediate layer - scp superior cerebellar peduncle - SCS superior colliculus, superficial layer - SGe suprageniculate nuc pons - SNC substantia nigra compact - SNL substantia nigra,lateral - SNR substantia nigra, reticular - SolL solitary tract nuc,lateral - SolM solitary tract nuc, medial - sp5 spinal tract trigeminal nerve - sp5I spinal trigeminal nuc, interpositus - Sp5O spinal trigeminal nuc, oral - spth spinothalamic tract - SpVe spinal vestibular nuc - SuVe superior vestibular nuc - tp tectopontine - ts tectospinal tract - tz trapezoid body - VCo ventral cochlear nuc - VLL ventral nuc lateral lemniscus - VPB ventral parabrachial nuc - vsc ventral spinocerebellar tract - VTA ventral tegmental area - VTg ventral tegmental nuc - vtgx ventral tegmental decussation - xscp decussation superior cerebellar peduncle This investigation was supported by grants from the Medical Research Council (MRC) of Canada (MT-6464: BEJ and MT 7376: AB). B.E. Jones holds a Chercheur Boursier Senior Award from the Fonds de la Recherche en Santé du Quebec (FRSQ), and A. Beaudet a Scientist Award from MRC     

Differences in mossy and climbing afferent sources between flocculus and ventral and dorsal paraflocculus in the rat

 Sources of mossy and climbing fiber inputs to the flocculus (FL), ventral paraflocculus (VP) and/or dorsal paraflocculus (DP) were identified in the vestibular ganglion, medulla oblongata and pons of 19 Wistar rats after 26 local injections of horseradish peroxidase, wheat-germ agglutinin-conjugated horseradish peroxidase, fast blue or diamidino yellow into the FL, VP and/or DP. There were large differences in the sources of mossy fibers to the FL and VP/DP. Labeled neurons after injections into the FL were observed mainly in the ipsilateral vestibular ganglion, bilaterally in the vestibular and prepositus hypoglossal nuclei, and in the caudal part of the nucleus reticularis tegmenti pontis. Labeled neurons were rarely observed in the pontine nuclei after localized injections into the FL. By contrast, after injections into the VP and/ or DP, numerous labeled neurons were observed in the pontine nuclei with a contralatetral predominance and in the rostral part of the nucleus reticularis tegmenti pontis bilaterally, but not in the vestibular nuclei in either side. Sources of climbing fibers to the FL and paraflocculus were completely contralateral to the injection side. After injection into the FL, labeled neurons were observed in the caudal dorsal cap and ventrolateral outgrowth of the inferior olivary nucleus. After injections into the VP, labeled neurons were observed mainly in the rostral dorsal cap, ventral medial accessory olivary nucleus (MAO) and caudal half of the ventral leaf of the principal olivary nucleus. After injections into the DP, labeled neurons were observed in the ventral MAO and caudal half of the ventral leaf of the principal olivary nucleus. These differences in the sources of mossy and climbing fiber inputs may suggest functional differences between the FL and VP/DP. The present results are consistent with our previous observations in monkey that the FL and VP/DP exhibit quite different mossy fiber input organizations. Received: 5 June 1998 / Accepted: 7 September 1998     

Pathways and terminations of axons arising in the fastigial oculomotor region of macaque monkeys.

The majority of axons from the fastigial oculomotor region (FOR) decussated in the cerebellum at all rostrocaudal levels of the fastigial nucleus (FN) and entered the brainstem via the contralateral uncinate fasciculus (UF). Some decussated axons separated from the UF and ran medial to the contralateral superior cerebellar peduncle and ascended to the midbrain. Uncrossed FOR axons advanced rostrolaterally in the ipsilateral FN and entered the brainstem via the juxtarestiform body. The decussated fibers terminated in the brainstem nuclei that are implicated in the control of saccadic eye movements. In the midbrain, labeled terminals were found in the rostral interstitial nucleus of the medial longitudinal fasciculus, a medial part of Forel's H-field, the periaqueductal gray, the posterior commissure nucleus, and the superior colliculus of the contralateral side. In the pons and medulla, FOR fibers terminated in a caudal part of the pontine raphe, the paramedian pontine reticular formation, the nucleus reticularis tegmenti pontis, the dorsomedial pontine nucleus of the contralateral side, and the dorsomedial medullary reticular formation of both sides. In contrast, FOR projections to the vestibular complex were bilateral and were mainly to the ventral portions of the lateral and inferior vestibular nuclei. No labeled terminals were found in the following brainstem nuclei which are considered to be involved in oculomotor function: oculomotor and trochlear nuclei, interstitial nucleus of Cajal, medial and superior vestibular nuclei, periphypoglossal nuclei, and dorsolateral pontine nucleus. Labeling appeared in the red nucleus only when HRP encroached upon the posterior interposed nucleus.     

Projections of brainstem core cholinergic and non-cholinergic neurons of cat to intralaminar and reticular thalamic nuclei

We combined the retrograde transport of wheat germ agglutinin conjugated with horseradish peroxidase with choline acetyltransferase immunohistochemistry to study the projections of cholinergic and non-cholinergic neurons of the upper brainstem core to rostral and caudal intralaminar thalamic nuclei, reticular thalamic complex and zona incerta in the cat. After wheat germ agglutinin-horseradish peroxidase injections in the rostral pole of the reticular thalamic nucleus, the distribution and amount of retrogradely labeled brainstem neurons were similar to those found after tracer injection in thalamic relay nuclei (see preceding paper). After wheat germ agglutinin-horseradish peroxidase injections in the caudal intralaminar centrum medianum-parafascicular complex, rostral intralaminar central lateral-paracentral wing, and zona incerta, the numbers of retrogradely labeled brainstem neurons were more than three times higher than those found after injections in thalamic relay nuclei. The larger numbers of horseradish peroxidase-positive brainstem reticular neurons after tracer injections in intralaminar or zona incerta injections results from a more substantial proportion of labeled neurons in the central tegmental field at rostral midbrain (perirubral) levels and in the ventromedial part of the pontine reticular formation, ipsi- and contralaterally to the injection site. Of all retrogradely labeled neurons in the caudal midbrain core at the level of the cholinergic peribrachial area and laterodorsal tegmental nucleus, 45-50% were also choline acetyltransferase-positive after the injections into central lateral-paracentral and reticular nuclei, while only 25% were also choline acetyltransferase-positive after the injection into the centrum medianum-parafascicular complex. These findings are discussed in the light of physiological evidence of brainstem cholinergic mechanisms involved in the blockade of synchronized oscillations and in activation processes of thalamocortical systems.     

Collateral projections of neurons from the lower part of the spinal cord to anterior and posterior cerebellar termination areas

Summary The collateral projections of spinocerebellar neurons located in the L 2 to Ca 1 spinal segments in the cat were investigated by retrograde fluorescent double labeling technique. Rhodamine labeled latex microspheres (Rm) and Fast Blue (FB) were used for injections into the cerebellum in 8 cats. Two additional cats, with injections of Fluoro-Gold (FG) combined with Rm were excluded because lipofuchsin autofluorescence obscured the labeling. After injections with one tracer unilaterally in the paramedian lobule and another tracer bilaterally in the anterior lobe, double labeled neurons were found on the side of the paramedian lobule injection in the column of Clarke at L 2–L 4, laminae IV–VI at L 2–L 5 and the dorsolateral nucleus at L 2–L 6. After bilateral injections of one tracer in lobule VIII B and another in the anterior lobe, double labeled neurons were found bilaterally in the column of Clarke at L 2–L 4, laminae IV–VI at L 2–L 5, the medial part of lamina VII at L 6–L 7 and in certain cell groups at sacro-coccygeal levels. Neurons in the lateral part of lamina VII at L 3–L 5 and the ventrolateral nucleus of L 4–L 5 were labeled exclusively from injections in the anterior lobe. The findings indicate that spinocerebellar neurons at lumbar and more caudal levels of the cat spinal cord have different projection patterns in the cerebellum. A certain number of neurons which project to the anterior lobe have divergent axon collaterals supplying also the posterior vermis and/or the paramedian lobule. Other neurons project to the anterior or to the posterior lobe only.Abbreviations CC column of Clarke - DL dorsolateral nucleus - FB Fast Blue - lam. lamina - lat. lateral - med. medial - N. f. fastigial nucleus - p. copul. pars copularis (paramedian lobule) - pfl.d. dorsal paraflocculus - pmd paramedian lobule - p.post pars posterior (paramedian lobule) - pyr. pyramis - Rm Rhodamine labeled latex microspheres - VL ventrolateral nucleus - I–IX (on cerebellar diagrams) cerebellar lobules, according to Larsell (1953) - A, B (following Roman numeral VIII) sublobules VIII A and VIII B - IV–IX (on spinal cord diagrams) laminae according to Rexed (1954) On leave from Capital Institute of Medicine, Beijing, The People's Republic of China     

The cerebellar projection from locus coeruleus as studied with retrograde transport of horseradish peroxidase in the cat

Summary The cerebellar afferent projection from locus coeruleus has been studied in the cat by means of retrograde axonal transport of horseradish peroxidase. Labelled cells are present bilaterally in locus coeruleus only following injections in the cerebellar vermis (especially its anterior and posterior parts), the ventral paraflocculus and the flocculus. The labelled cells are restricted to the caudal half of the nucleus.A few labelled cells are also present in locus coeruleus following injections in the fastigial nucleus, and in nucleus interpositus anterior. The findings are discussed in relation to other studies on the efferent and afferent connections of the locus coeruleus.On leave from the Laboratory of Neurobiology and Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand, under the Fellowship Program of the Norwegian Agency for International Development (NORAD)     

An autoradiographic analysis of ascending projections from the medullary reticular formation in the rat

Ascending projections from the several nuclei of the medullary reticular formation were examined using the autoradiographic method. The majority of fibers labeled after injections of [3H]leucine into nucleus gigantocellularis ascended within Forel's tractus fasciculorum tegmenti which is located ventrolateral to the medial longitudinal fasciculus. Nucleus gigantocellularis injections produced heavy labeling in the pontomesencephalic reticular formation, the intermediate layers of the superior colliculus, the pontine and midbrain central gray, the anterior pretectal nucleus, the ventral midbrain tegmentum including the retrorubral area, the centromedian-parafascicular complex, the fields of Forel/zona incerta, the rostral intralaminar nuclei and the lateral hypothalamic area. Nucleus gigantocellularis projections to the rostral forebrain were sparse. Labeled fibers from nucleus reticularis ventralis, like those from nucleus gigantocellularis, ascended largely in the tracts of Forel and distributed to the pontomedullary reticular core, the facial and trigeminal motor nuclei, the pontine nuclei and the dorsolateral pontine tegmentum including the locus coeruleus and the parabrachial complex. Although projections from nucleus reticularis ventralis diminished significantly rostral to the pons, labeling was still demonstrable in several mesodiencephalic nuclei including the cuneiform-pedunculopontine area, the mesencephalic gray, the superior colliculus, the anterior pretectal nucleus, the zona incerta and the paraventricular and intralaminar thalamic nuclei. The main bundle of fibers labeled by nucleus gigantocellularis-pars alpha injections ascended ventromedially through the brainstem, just dorsal to the pyramidal tracts, and joined Forel's tegmental tract in the midbrain. With the brainstem, labeled fibers distributed to the pontomedullary reticular formation, the locus coeruleus, the raphe pontis, the pontine nuclei, and the dorsolateral tegmental nucleus and adjacent regions of the pontine gray. At mesodiencephalic levels, labeling was present in the rostral raphe nuclei (dorsal, median and linearis), the mesencephalic gray, the deep and intermediate layers of the superior colliculus, the medial and anterior pretectal nuclei, the ventral tegmental area, zona incerta as well as the mediodorsal and reticular nuclei of the thalamus. Injections of the parvocellular reticular nucleus labeled axons which coursed through the lateral medullary tegmentum to heavily innervate lateral regions of the medullary and caudal pontine reticular formation, cranial motor nuclei (hypoglossal, facial and trigeminal) and the parabrachial complex.(ABSTRACT TRUNCATED AT 400 WORDS)     

Multiple forebrain systems converge on motor neurons innervating the thyroarytenoid muscle

The present study investigated the central connections of motor neurons innervating the thyroarytenoid laryngeal muscle that is active in swallowing, respiration and vocalization. In both intact and sympathectomized rats, the pseudorabies virus (PRV) was inoculated into the muscle. After initial infection of laryngomotor neurons in the ipsilateral loose division of the nucleus ambiguus (NA) by 3 days post-inoculation, PRV spread to the ipsilateral compact portion of the NA, the central and intermediate divisions of the nucleus tractus solitarii, the Botzinger complex, and the parvicellular reticular formation by 4 days. Infection was subsequently expanded to include the ipsilateral granular and dysgranular parietal insular cortex, the ipsilateral medial division of the central nucleus of the amygdala, the lateral, paraventricular, ventrolateral and medial preoptic nuclei of the hypothalamus (generally bilaterally), the lateral periaqueductal gray, the A7 and oral and caudal pontine nuclei. At the latest time points sampled post-inoculation (5 days), infected neurons were identified in the ipsilateral agranular insular cortex, the caudal parietal insular cortex, the anterior cingulate cortex, and the contralateral motor cortex. In the amygdala, infection had spread to the lateral central nucleus and the parvicellular portion of the basolateral nucleus. Hypothalamic infection was largely characterized by an increase in the number of infected cells in earlier infected regions though the posterior, dorsomedial, tuberomammillary and mammillary nuclei contained infected cells. Comparison with previous connectional data suggests PRV followed three interconnected systems originating in the forebrain; a bilateral system including the ventral anterior cingulate cortex, periaqueductal gray and ventral respiratory group; an ipsilateral system involving the parietal insular cortex, central nucleus of the amygdala and parvicellular reticular formation, and a minor contralateral system originating in motor cortex. Hypothalamic innervation involved several functionally specific nuclei. Overall, the data imply complex CNS control over the multi-functional thyroarytenoid muscle.     

Afferent and efferent connections of the ventrolateral tegmental area in the rat

 The present study examined the organization of afferent and efferent connections of the rat ventrolateral tegmental area (VLTg) by employing the retrograde and anterograde axonal transport of Fluorogold and Phaseolus vulgaris-leucoagglutinin, respectively. Our interest was focused on whether the anatomical connections of the VLTg would provide evidence as to the involvement of this reticular area in audiomotor behavior. Our retrograde experiments revealed that minor inputs to the VLTg arise in various telencephalic structures, including the cerebral cortex. Stronger projections originate in the lateral preoptic area, the zona incerta, the nucleus of the posterior commissure and some other thalamic areas, the lateral substantia nigra, the deep layers of the superior colliculus, the dorsal and lateral central gray, the deep mesencephalic nucleus, the paralemniscal zone, the intercollicular nucleus, the external cortex of the inferior colliculus, the oral and caudal pontine reticular nucleus, the deep cerebellar nuclei, the gigantocellular and lateral paragigantocellular reticular nuclei, the prepositus hypoglossal nucleus, the spinal trigeminal nuclei, and the intermediate layers of the spinal cord. Most importantly, we disclosed strong auditory afferents arising in the dorsal and ventral cochlear nuclei and in the cochlear root nucleus. The efferent projections of the VLTg were found to be less widespread. Telencephalic structures do not receive any input from the VLTg. Moderate projections were seen to diencephalic reticular areas, the zona incerta, the nucleus of the posterior commissure, and to various other thalamic areas. The major VLTg projections terminate in the deep layers of the superior colliculus, the deep mesencephalic nucleus, the intercollicular nucleus and external cortex of the inferior colliculus, the oral and caudal pontine reticular nucleus, the gigantocellular and lateral paragigantocellular reticular nuclei, and in the medial column of the facial nucleus. From our data, we conclude that the VLTg might play a role in sensorimotor behavior. Accepted: 3 April 1997     

The cells of origin of the incertofugal projections to the tectum,thalamus, tegmentum and spinal cord in the rat: A study using the autoradiographic and horseradish peroxidase methods

Efferent projections of the zona incerta were examined in the rat using the autoradiographic and horseradish peroxidase methods, with special reference to the cytoarchitectonic structure of the zona incerta.Autoradiographic experiments showed that the incertofugal fiber systems reach ipsilaterally to the thalamus (lateral dorsal, central lateral, ventral lateral geniculate, parafascicular, subparafascicular and reuniens nuclei, and posterior nuclear complex), to the hypothalamus (dorsal, lateral and posterior hypothalamic areas), to the tectum (medial pretectal area, deep pretectal and pretectal nuclei, superior colliculus and periaqueductal gray) and to the midbrain tegmentum, pons and medulla oblongata (subcuneiform, cuneiform and red nuclei, nuclei of the posterior commissure and Darkschewitsch, interstitial nucleus of Cajal, pedunculopontine tegmental nucleus, oral and caudal pontine reticular nuclei, nucleus raphe magnus, gigantocellular reticular nucleus, pontine gray and inferior olivary complex). Contralaterally, incertal efferent fibers reach to the zona incerta.Cells of origin of the incertofugal fiber systems to the tectum, thalamus, tegmentum and spinal cord were examined using the retrograde horseradish peroxidase method. Cells of origin of the incertotectal pathway are located mainly in the ventral and caudal parts of the zona incerta and partly in the antero-polar, dorsal and postero-polar parts. Cells projecting to the thalamus (at least to the lateral dorsal and central lateral nuclei) are situated in the ventral and caudal parts of the zona incerta, but they are rare in the other incertal structures. Cells of origin of the incertotegmental system are located mainly in the dorsal, magnocellular and caudal parts and partly in the antero- and postero-polar parts, but they are not situated in the ventral part. Cells of the magnocellular part project more caudally to the medulla oblongata and spinal cord than those of the other parts of the zona incerta. Forel's field contains many cells projecting to the tegmentum.The results provide good evidence that the cells of origin of efferent projections are topographically organized and are related to cytoarchitectonic areas within the zona incerta.     

Retrograde labeling of neurons in the brain stem following injections of [3H]choline into the rat spinal cord

In an attempt to identify cholinergic neurons in the brain stem which project to the spinal cord, [3H]choline (100, 20, 10, 5 or 1 microCi) was injected into the upper cervical spinal cord in 55 rats. The animals were killed 20 h later and the brains processed for autoradiography of diffusible substances. At all doses of [3H]choline, cells were consistently, retrogradely labeled in the medical medullary reticular formation, the lateral vestibular nucleus, the dorsolateral pontine tegmentum and the red nucleus. The retrogradely labeled cells were found to be moderately to darkly stained for acetylcholinesterase. Injection of [3H]noradrenaline (50 microCi) into the upper cervical spinal cord resulted in retrograde labeling of cells in the locus coeruleus, subcoeruleus and the ventrolateral pontine tegmentum, that correspond in position to the neurons of the A6, A7 and A5 catecholamine cell groups, respectively. Injection of [3H]serotonin (20 microCi) into the upper cervical spinal cord was associated with retrograde labeling of cells in the raphe pallidus, obscurus and magnus nuclei that correspond in position to those of the B1, B2 and B3 serotonin cell groups, respectively. Injection of True Blue into the upper cervical spinal cord was followed by retrograde labeling of a large number of cells located in the areas where cells were retrogradely labeled by [3H]choline, [3H]noradrenaline and [3H]serotonin, and additionally, in the solitary tract nucleus, the lateral, parvicellular medullary reticular formation, the caudal and oral pontine reticular formation, the mesencephalic reticular formation and the superior colliculus. These results indicate that from the cervical spinal cord, [3H]choline selectively retrogradely labels a certain population of non-monaminergic, acetylcholinesterase-positive cells localized in the medial medullary, and secondarily the dorsolateral pontine, reticular formation, the lateral vestibular nucleus, and the red nucleus.