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)     

The differential descending projections from the anterior, central and posterior regions of the lateral hypothalamic area: an autoradiographic study

The descending projection sites of the anterior, central (or tuberal) and posterior regions of the lateral hypothalamic area were studied by anterograde axonal transport after local injection of tritiated amino acids. The results show that the neurons of the anterior regions project to the lateral mammillary nucleus, the ventral tegmental area, the midbrain central gray and the anterior parts of the dorsal raphe nucleus. The neurons of the central region project in the same structures and extend a projection into the dorsal tegmentum at the level of the pontine central gray, the midbrain and pontine reticular nuclei. In the ventral tegmentum region, the substantia nigra pars compacta, the interpeduncular nucleus and the anterior group of raphe nuclei were also found to be labelled. The neurons of the posterior region of the lateral hypothalamic area extend a projection to the level of the prepositus hypoglossi nucleus and to the nucleus of solitary tract. In the ventral tegmentum they project at the level of posterior group of the raphe nuclei and the inferior olivary complex.     

A lectin horseradish peroxidase study of the origin of ascending fibers in the medial forebrain bundle of the rat. The upper brainstem

The origins of projections within the medial forebrain bundle from the upper brainstem were examined with the horseradish peroxidase technique. Labeled cells were found in approximately 15 upper brainstem nuclei following injections of a conjugate of horseradish peroxidase and wheat germ agglutinin at various levels of the medial forebrain bundle. Labeled nuclei included (from caudal to rostral): dorsal and ventral parabrachial nuclei; Kolliker-Fuse nucleus; dorsolateral tegmental nucleus; A7 (lateral pontine tegmentum medial to lateral lemniscus); median and dorsal raphe nuclei; distinct group of cells oriented mediolaterally in the dorsal pontine tegmentum below the central gray; B9 (ventral midbrain tegmentum dorsal to medial lemniscus); retrorubral nucleus; nucleus of Darkschewitsch, interfascicular nucleus; rostral and caudal linear nuclei; ventral tegmental area; medial part of substantia nigra, pars compacta; and the supramammillary nucleus. With the exception of the ventral parabrachial nucleus, Kolliker-Fuse, A7, B9 and substantia nigra, pars compacta, each of the nuclei mentioned above sent strong projections along the medial forebrain bundle to the rostral forebrain. Sparse labeling was observed throughout the pontine and midbrain reticular formation. With the exception of the dorsal raphe nucleus, projections to the most anterior regions of the medial forebrain bundle (level of the anterior commissure) essentially only arose from presumed dopamine-containing nuclei-retrorubral nucleus (A8 area), interfascicular nucleus, rostral and caudal linear nuclei, substantia nigra pars compacta, and ventral tegmental area. Evidence was reviewed indicating that major forebrain sites of termination for these dopaminergic nuclei are structures that have been collectively referred to as the 'ventral striatum'. It is concluded from the present findings that several pontine and mesencephalic cell groups are in a position to exert a strong, direct effect on structures in the anterior forebrain and that the medial forebrain bundle is the main communication route between the upper brainstem and the forebrain.     

Distribution of premotor neurons for the hypoglossal nucleus in the cat

After injecting horseradish peroxidase into the hypoglossal nucleus, labeled neuronal cell bodies were constantly seen bilaterally with a slight ipsilateral dominance in the parvocellular reticular formation and reticular regions around the hypoglossal nucleus, ipsilaterally in the nucleus of K?lliker-Fuse, and contralaterally within the hypoglossal nucleus. A few labeled neurons were often found bilaterally with an ipsilateral dominance in the inter- and supratrigeminal regions around the motor trigeminal nucleus, parabrachial nucleus, ventral portions of the medial reticular formation of the pons and medulla oblongata, and dorsal tegmental regions and central gray of the midbrain.     

The cerebellar projection from the reticular formation of the brain stem in the rabbit

Summary By retrograde transport of horseradish peroxidase the reticulocerebellar projections were examined in twenty-six rabbits.After injections in the cerebellum retrogradely labeled neurons were more numerous in the caudal reticular formation (ventral and gigantocellular reticular nuclei) than in its rostral part (caudal and oral pontine reticular nuclei). The labeled cells were of all sizes, large, medium-sized and small. Giant cells were labeled only after injections in the posterior lobe vermis.After injections in the anterior lobe, the posterior vermis, the fastigial nucleus and the flocculus, retrogradely labeled neurons were found bilaterally in the ventral reticular nucleus, the gigantocellular reticular nucleus and the caudal pontine reticular nucleus. Some cases with posterior vermal and fastigial injections in addition showed labeled neurons bilaterally in the oral pontine reticular nucleus. There were no major side differences. The cases with injections in the anterior part of the paramedian lobule gave rise to only a few labeled cells in the gigantocellular reticular nucleus.Negative findings were consistently made in the mesencephalic reticular formation.     

Distribution of premotor neurons for orbicularis oculi motoneurons in the cat, with particular reference to possible pathways for blink reflex

After injecting horseradish peroxidase into the facial nucleus regions containing orbicularis oculi motoneurons, labeled neuronal cell bodies were found in the lateral medullary reticular formation, pretectal olivary nucleus, sensory trigeminal nuclei, lateral and medial parabrachial nuclei, ventromedial reticular formation medial to the facial nucleus, red nucleus and its surroundings, anterior horn of the upper cervical cord, medullary raphe nuclei, oculomotor nucleus and its surroundings, nuclei of Darkschewitsch, Cajal and Edinger-Westphal, ventral part of the midbrain central gray, pontine tegmentum, lateral vestibular nucleus and deep layers of the superior colliculus.     

大鼠终纹床核卵圆核及其邻近区域的传出纤维联系——WGA-HRP顺行追踪法研究

本实验选用150～260g的雄性Sprague-Dawley大鼠13只,把WGA-HRP/HRP混合水溶液加压注入一侧终纹床核群前外侧区的卵圆核区域,冰冻切片,TMB法呈色后,在中枢看到顺行标记终末最密集的部位是:下丘脑后部外侧区、中央杏仁核、中脑中央灰质、臂旁核、三叉神经中脑核、蓝斑;比较多的部位是视前区、下丘脑室周区、弓状核、丘脑中线核群、内侧纽核、腹侧背盖核、脚桥背盖核、中脑网状结构、中缝背核以及迷走神经复合体;在线形中缝核、中央上核、腹侧背盖区、黑质,以及延髓中介核,也看到少量标记终末。本工作对卵圆核的传出纤维联系,进行了较全面的观察。     

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     

Amygdaloid projections to the mesencephalon,pons and medulla oblongata in the cat

Summary Amygdalotegmental projections were studied in 26 cats after injections of horseradish peroxidase (HRP) in the diencephalon, midbrain and lower brain stem and in 6 cats after injection of ³H-leucine in the amygdala. Following HRP injections in the posterior hypothalamus, periaqueductal gray (PAG) and tegmentum many retrogradely labeled neurons were present in the central nucleus (CE) of the amygdala, primarily ipsilaterally. Injections of HRP in the posterior hypothalamus and mesencephalon also resulted in the labeling of neurons in the basal nucleus, pars magnocellularis.Following ³H-leucine injections in CE and adjacent structures autoradiographically labeled fibers were present in the stria terminalis and ventral amygdalofugal pathways. In the mesencephalon heavily labeled fiber bundles were located lateral to the red nucleus. Labeled fibers and terminals were distributed to the mesencephalic reticular formation, substantia nigra, ventral tegmental area and PAG. In the pontine and medullary tegmentum the bulk of passing fibers was located laterally in the reticular formation. Many labeled fibers and terminals were distributed to the parabrachial nuclei, locus coeruleus, nucleus subcoeruleus and lateral tegmental fields. Many terminals were also present in the solitary nucleus and dorsal motor nucleus of the vagus nerve.The location of the cells of origin and the distribution of the terminals of the amygdalotegmental projection suggest that this pathway plays an important role in the integration of somatic and autonomic responses associated with affective defense.Abbreviations A nucleus ambiguus - AL lateral amygdaloid nucleus - AQ cerebral aqueduct - BC brachium conjunctivum - BL basal amygdaloid nucleus, pars magnocellularis - BM basal amygdaloid nucleus, pars parvocellularis - BP brachium pontis - CE central amygdaloid nucleus - CI internal capsule - CN cochlear nucleus - CO cortical amygdaloid nucleus - CP cerebral peduncle - DCN dorsal column nuclei - DMV dorsal motor nucleus of the vagus nerve - E entopeduncular nucleus - F fornix - FLA longitudinal association bundle - GP globus pallidus - H hippocampal formation - 1C inferior colliculus - INJ injection site - LC locus coeruleus - IO inferior olive - LG lateral geniculate nucleus - LRN lateral reticular nucleus - LT lateral tegmental field - M medial amygdaloid nucleus - MB mammilary body - MG medial geniculate nucleus - ML medial lemniscus - MT medial tegmental field - MV motor nucleus of the trigeminus - OC optic chiasm - OT optic tract - P putamen - PAG periaqueductal gray - PB parabrachial nuclei - PC posterior commissure - PH posterior hypothalamus - PT pyramidal tract - PV principal sensory nucleus of the trigeminus - PYR pyriform cortex - R red nucleus - RF reticular formation - S solitary nucleus - SC nucleus subcoeruleus - SN substantia nigra - SO superior olive - SOL solitary nucleus - SPV spinal trigeminal complex - ST stria terminalis - VC vestibular complex - VTA ventral tegmental area - VII facial nucleus - XII hypoglossal nucleus     

Neurotoxic N-methyl-D-aspartate lesion of the ventral midbrain and mesopontine junction alters sleep-wake organization

The dorsal regions of the midbrain and pons have been found to participate in sleep regulation. However, the physiological role of the ventral brainstem in sleep regulation remains unclear. We used N-methyl-D-aspartate-induced lesions of the ventral midbrain and pons to address this question. Unlike dorsal mesencephalic reticular formation lesions, which produce somnolence and electroencephalogram synchronization, we found that ventral midbrain lesions produce insomnia and hyperactivity. Marked increases in waking and decreases in slow wave sleep stage 1 (S1), stage 2 (S2) and rapid eye movement sleep were found immediately after the lesion. Sleep gradually increased, but never returned to baseline levels (baseline/month 1 post-lesion: waking, 30.6 +/- 4.58%/62.3 +/- 10.1%; S1, 5.1 +/- 0.74/3.9 +/- 1.91%; S2, 46.2 +/- 4.74%/23.1 +/- 5.47%; rapid eye movement sleep, 14.1 +/- 3.15%/7.2 +/- 5.42%). These changes are comparable in magnitude to those seen after basal forebrain lesions. Neuronal degeneration was found in the ventral rostral pons and midbrain, including the substantia nigra, ventral tegmental area, retrorubral nucleus, and ventral mesencephalic and rostroventral pontine reticular formation. We conclude that nuclei within the ventral mesencephalon and rostroventral pons play an important role in sleep regulation.     

Projections of cholinergic and non-cholinergic neurons of the brainstem core to relay and associational thalamic nuclei in the cat and macaque monkey

The projections of brainstem core neurons to relay and associational thalamic nuclei were studied in the cat and macaque monkey by combining the retrograde transport of wheat germ agglutinin conjugated with horseradish peroxidase with choline acetyltransferase immunohistochemistry. All major sensory (medial geniculate, lateral geniculate, ventrobasal), motor (ventroanterior, ventrolateral, ventromedial), associational (mediodorsal, pulvinar, lateral posterior) and limbic (anteromedial, anteroventral) thalamic nuclei of the cat were found to receive projections from cholinergic neurons located in the peribrachial area of the pedunculopontine nucleus and in the laterodorsal tegmental nucleus as well as from non-cholinergic neurons in the rostral (perirubral) part of the central tegmental mesencephalic field. Specific relay nuclei receive less than 10% of their brainstem afferents from non-cholinergic neurons located at rostral midbrain levels and receive 85-96% of their brainstem innervation from a region at midbrain-pontine junction where the cholinergic peribrachial area and laterodorsal tegmental nucleus are maximally developed. Of the total number of horseradish peroxidase-positive brainstem neurons seen after injections in various specific relay nuclei, the double-labeled (horseradish peroxidase + choline acetyltransferase) neurons represent approximately 70-85%. Three to eight times more numerous horseradish peroxidase-labeled brainstem cells were found after injections in associational (mediodorsal and pulvinar-lateral posterior complex) and diffusely cortically-projecting (ventromedial) thalamic nuclei of cat than after injections in specific relay nuclei. The striking retrograde cell labeling observed after injections in nuclei with associative functions and widespread cortical projections was due to massive afferentation from non-cholinergic parts of the midbrain and pontine reticular formation, on both ipsi- and contralateral sides. After wheat germ agglutinin-horseradish peroxidase injections in the associative pulvinar-lateral posterior complex and mediodorsal nucleus of Macaca sylvana, 45-50% of horseradish peroxidase-positive brainstem peribrachial neurons were also choline acetyltransferase-positive. While cells in the medial part of the cholinergic peribrachial area were found to project especially towards the pulvinar-lateral posterior nuclear complex in monkey, the retrograde cell labeling seen after the mediodorsal injection was mostly confined to the lateral part of both dorsal and ventral aspects of the peribrachial area.(ABSTRACT TRUNCATED AT 400 WORDS)     

Brain stem neurons projecting to neocortex: A HRP study in the cat

Summary The cortical projections of the brain stem were investigated in detail in the cat by means of the horseradish peroxidase (HRP) retrograde axonal transport. Most of the cells providing ascending fibers to the neocortex were located in the pons (locus coeruleus and related structures, central gray substance, dorsal tegmental nucleus, raphe nuclei, reticular nuclei); labeled neurons were also identified in the mesencephalon, mainly in the periaqueductal gray and in the nucleus linearis rostralis. These projections, and particularly the pontine fibers, were diffusely distributed throughout the cerebral cortex.The results are compared with the data previously obtained by the use of anterograde and retrograde tracing techniques.     

GABA and glycine as putative transmitters in subcortical pathways to the pontine nuclei. A combined immunocytochemical and retrograde tracing study in the cat with some observations in the rat.

Using the retrograde tracers horseradish peroxidase-wheatgerm agglutinin and gold particles conjugated to wheatgerm agglutinin apo-horseradish peroxidase in combination with an antiserum against glutaraldehyde-fixed GABA, it was examined whether the pontine nuclei of the cat receive projections from GABA-like immunoreactive neurons in the brainstem, diencephalon, or deep cerebellar nuclei, contributing to the GABA-like immunoreactive fibre plexus previously demonstrated in the pontine nuclei [Brodal et al. (1988) Neuroscience 25, 27-45]. Following tracer injections that covered both the pontine nuclei and the reticular tegmental nucleus in two cats, it was found that 125 out of 1166 (10.7%) and 29 out of 294 (9.9%) retrogradely labelled neurons in the cerebellar nuclei were GABA-like immunoreactive. In the same two experiments only six out of 2029 (0.3%) and 10 out of 1398 (0.7%) retrogradely labelled neurons in the brainstem and diencephalon were GABA-like immunoreactive. Among the regions in the brainstem and diencephalon known to project to the pontine nuclei, double-labelled cells were seen in the reticular formation, the periaqueductal gray, and the nucleus praepositus hypoglossi, but not in the zona incerta or the anterior pretectal nucleus, regions that have been shown to contain glutamate decarboxylase-like immunoreactive neurons projecting to the pontine nuclei in the rat [Border et al. (1986) Brain Res. Bull. 17, 169-179]. In order to test whether this is due to species differences, the same experimental approach was used in the rat, and it was found that 54 out of 3249 (1.7%) retrogradely labelled neurons in the brainstem and diencephalon were double-labelled. Notably, in the zona incerta 2% of the retrogradely labelled cells were also GABA-like immunoreactive, and in the reticular formation there was a higher proportion of double-labelled cells than was found in the cat. Additional sources were identified, that may contribute to the GABA-like immunoreactive fibre plexus in the pontine nuclei of the rat. This, in conjunction with the previous finding that the pontine nuclei of the rat contain only very few putative GABAergic neurons [Border and Mihailoff (1985) Expl Brain Res. 59, 600-614; Brodal et al. (1988) Neuroscience 25, 27-45], lead to the suggestion that the GABA-like immunoreactive fibre plexus in the pontine nuclei of the rat is predominantly of extrinsic origin, possibly representing a mosaic of the terminal fields of several subcorticopontine projections.(ABSTRACT TRUNCATED AT 400 WORDS)     

Glutaminase-like immunoreactivity in the lower brainstem and cerebellum of the adult rat

Distribution of putative glutamatergic neurons in the lower brainstem and cerebellum of the rat was examined immunocytochemically by using a monoclonal antibody against phosphate-activated glutaminase, which has been proposed to be a major synthetic enzyme of transmitter glutamate and so may serve as a marker for glutamatergic neurons in the central nervous system. Intensely-immunolabeled neuronal cell bodies were densely distributed in the main precerebellar nuclei sending mossy fibers to the cerebellum; in the pontine nuclei, pontine tegmental reticular nucleus of Bechterew, external cuneate nucleus, and lateral reticular nucleus of the medulla oblongata. Phosphate-activated glutaminase-immunoreactive granular deposits were densely seen in the brachium pontis and restiform body, suggesting the immunolabeling of mossy fibers of passage. In the cerebellum, neuropil within the granule cell layer of the cerebellar cortex displayed intense phosphate-activated glutaminase-immunoreactivity, and that within the deep cerebellar nuclei showed moderate immunoreactivity. These results indicate that many mossy fiber terminals originate from phosphate-activated glutaminase-containing neurons and utilize phosphate-activated glutaminase for the synthesis of transmitter glutamate. Intensely-immunostained neuronal cell bodies were further observed in other regions which have been reported to contain neurons sending mossy fibers to the cerebellum; in the dorsal part of the principal sensory trigeminal nucleus, dorsomedial part of the oral subnucleus of the spinal trigeminal nucleus, interpolar subnucleus of the spinal trigeminal nucleus, paratrigeminal nucleus, supragenual nucleus, regions dorsal to the abducens nucleus and genu of the facial nerve, superior and medial vestibular nuclei, cell groups f, x and y, hypoglossal prepositus nucleus, intercalated nucleus, nucleus of Roller, reticular regions intercalated between the motor trigeminal and principal sensory trigeminal nuclei, linear nucleus, and gigantocellular and paramedian reticular formation. Neuronal cell bodies with intense phosphate-activated glutaminase-immunoreactivity were also found in other brainstem regions, such as the paracochlear glial substance, posterior ventral cochlear nucleus, and cell group e. Although it is still controversial whether all glutamatergic neurons use phosphate-activated glutaminase in a transmitter-related process and whether phosphate-activated glutaminase is involved in other metabolism-related processes, the neurons showing intense phosphate-activated glutaminase-immunoreactivity in the present study were suggested to be putative glutamatergic neurons.     

Substance P: localization within paleostriatal-tegmental pathways in the pigeon

Immunohistochemical techniques were used to determine the distribution of substance P-like immunoreactivity within the paleostriatal complex and within the projection targets of the paleostriatal complex in the pigeon. The density of substance P-like immunoreactivity was found to be much greater in the paleostriatal complex than in immediately overlying portions of the telencephalon (such as the neostriatum and ectostriatum). The small-celled zone of the paleostriatal complex (equivalent to the mammalian caudate-putamen) is characterized by the presence of numerous neurons and fibers that show intense substance P-like immunoreactivity. A higher density of neurons containing substance P-like immunoreactivity was observed within the more medial subdivision of the small-celled zone of the paleostriatal complex (termed the lobus parolfactorius), than in the more lateral subdivision of the small-celled zone of the paleostriatal complex (termed the paleostriatum augmentatum). Many of the substance P-containing fibers within the neuropil of lobus parolfactorius and paleostriatum augmentatum appeared to represent the processes of the substance P-containing neurons of those regions. A dense network of seemingly thick, coarse substance P-containing fibers was observed in the large-celled zone of the avian paleostriatal complex (termed the paleostriatum primitivum). A few medium-sized substance P-containing neurons were evident in the latter area.In addition to fine substance P-containing fibers, numerous thick substance P-immunoreactive fibers were observed in the lobus parolfactorius. The substance P-containing fibers of this region appeared to contribute to a dense substance P-containing fiber plexus in the ventromedial floor of the telencephalon. This region, through which the medial forebrain bundle courses, has been termed the ventral paleostriatum by Kitt &; Brauth.³⁶ The medial forebrain bundle could be traced as a substance P-positive fiber bundle from within the ventral paleostriatum to the midbrain tegmentum. Within the midbrain tegmentum, the fibers of the medial forebrain bundle could be traced into prominent substance P-immunoreactive terminal fields over the cell bodies and neuropil of the catecholaminergic cell groups of the tegmentum, including the ventral tegmental area of Tsai and the nucleus tegmentipedunculopontinus. Within the latter nucleus, substance P-containing fibers and terminals were most densely concentrated within the dorsomedial portion of the nucleus. Kitt &; Brauth³⁶have recently shown by horseradish peroxidase and autoradiographic pathway tracing techniques that the lobus parolfactorius projects to the portions of the ventral tegmental area and nucleus pedunculopontinus that were observed to contain a dense field of substance P-containing fibers and terminals. Unilateral knife cuts of the medial forebrain bundle at rostral diencephalic levels were found to eliminate nearly totally the substance P-immunoreactivity from the neuropil of the ventral tegmental area and nucleus pendunculopontinus on the ipsilateral side of the brain.The present findings argue that, as in mammals, portions of the small-celled zone of the basal ganglia (or paleostriatal complex) in birds may utilize substance P as a neurotransmitter or modulator in their projections upon catecholaminergic cell groups of the midbrain. The present data further suggest that the lobus parolfactorius and paleostriatum augmentatum together in birds are to be considered equivalent to the mammalian caudate-putamen and nucleus accumbens. Previous studies had only emphasized the similarity of paleostriatum augmentatum to the mammalian caudate-putamen.^4,33     

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 afferent projections to the midbrain periaqueductal gray of the rat

The retrograde transport technique was utilized in the present study to investigate the afferent projections to the periaqueductal gray of the rat. Iontophoretic injections of horseradish peroxidase were made into the periaqueductal gray of 22 experimental animals and into regions adjacent to the periaqueductal gray in 6 control animals. Utilization of the retrograde transport method permitted a quantitative analysis of the afferent projections not only to the entire periaqueductal gray, but also to each of its four intrinsic subdivisions. The largest cortical input to this midbrain region arises from areas 24 and 32 in the medial prefrontal cortex. The basal forebrain provides a significant input to the periaqueductal gray and this arises predominantly from the ipsilateral lateral and medial preoptic areas and from the horizontal limb of the diagonal band of Broca. The hypothalamus was found to provide the largest descending input to the central gray. Numerous labeled cells occurred in the ventromedial hypothalamic nucleus, the lateral hypothalamic area, the posterior hypothalamic area, the anterior hypothalamic area, the perifornical nucleus and the area of the tuber cinereum. The largest mesencephalic input to the periaqueductal gray arises from the nucleus cuneiformis and the substantia nigra. The periaqueductal gray was found to have numerous intrinsic connections and contained a significant number of labeled cells both above and below the injection site in each case. Other structures containing significant label in the midbrain and isthmus region included the nucleus subcuneiformis, the ventral tegmental area, the locus coeruleus and the parabrachial nuclei. The medullary and pontine reticular formation provide the largest input to the periaqueductal gray from the lower brain stem. The midline raphe magnus and superior central nucleus also supply a significant fiber projection to the central gray. Both the trigeminal complex and the spinal cord provide a minor input to this region of the midbrain.The sources of afferent projections to the periaqueductal gray are extensive and allow this midbrain region to be influenced by motor, sensory and limbic structures. In addition, evidence is provided which indicates that the four subdivisions of the central gray receive differential projections from the brain stem as well as from higher brain structures.     

大鼠脑干神经元型一氧化氮合酶免疫阳性神经元的分布

目的　观察大鼠脑干神经元型一氧化氮合酶 (nNOS)免疫阳性神经元的分布 ,为探讨nNOS的作用提供形态学资料。方法　用ABC免疫细胞化学方法显示脑干nNOS免疫阳性神经元。结果　大鼠脑干nNOS免疫阳性神经元以中脑和脑桥分布丰富 ,延髓较稀少 ;在中脑 ,nNOS免疫阳性神经元主要分布于中脑水管周围灰质的背侧部、被盖背外侧核、中缝背核、上下丘灰质等部位 ;在脑桥 ,主要分布于被盖背外侧核、脑桥中缝核、被盖脚桥核、蓝斑、臂旁核、斜方体核 ,以及脑桥网状结构 ;与中脑和脑桥相比 ,延髓nNOS免疫阳性神经元较少 ,主要分布于延髓网状结构、三叉神经脊束核和孤束核等核团。结论　分布于脑干内丰富的nNOS免疫阳性神经元可能通过其生成的NO调节其他神经递质的分泌 ,共同参与内脏活动、感觉和运动的传导 ,以及睡眠和觉醒等脑的高级整合功能的调节。     

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.     

树鼩脑干儿茶酚胺神经元的分布

应用FAGLU荧光组化技术观察了树鼩脑干儿茶酚胺神经元(简称CA神经元)的位置分布及其形态特征。结果表明,CA神经元主要分布于下列核区:延髓的腹外侧网状核(LRN),孤束核(Sol);脑桥的面神经核(nVll).脑桥尾侧网状校(PnC),第四脑室顶外侧壁,蓝斑(Lc),脑桥头端与中脑尾端移行部的中缝背核(DR)、中央上核(cs),腹外侧臂旁核(VLPB)、中央灰质腹侧(Vcg);中脑的黑质(SN)、和腹侧被盖区(VTA)。