Electrophysiological peculiarities of cortical inputs to the cat red nucleus

Complex multicomponent EPSPs of the red nucleus rubro-spinal neurons evoked by stimulation of the sensorimotor cortex and associative fields of the parietal cortex were studied in acute pentobarbitalized cats by intracellular recording technique. Complex cortical EPSPs were recorded in 2/3 of the neurons studied. Components of the EPSPs in question were distinguished by using stimulation of various frequency and intensity. The first component of the EPSPs appearing at the lowest threshold was found to have a short and stable latency, stable rising time for depolarization and was able to follow high frequencies of stimulation. The second component was more variable, although in some EPSPs it too had a short latency, was stable enough and, like the first component could be classified as monosynaptic. The complex character of the EPSPs recorded persisted after the removal of the cerebral gray and was observed when stimulating the white matter so excluding its cortical origin. The first two components of the EPSP were evoked by corticofugal impulsation propagating at an average velocity of 18.5 m/s and 7.5 m/s being supposedly the result of activation of the slow-conducting pyramidal and cortico-rubral neurons. In some rubro-spinal neurons they were characterized by a fast rising phase being apparently an electrophysiological manifestation of the activation of axosomatic synapses.     

Sizes, laminar and topographic origins of cortical projections to the major divisions of the red nucleus in the monkey

The retrograde transport of horseradish peroxidase was used to study the topographic and laminar origins of the cortical projections to the parvocellular and the magnocellular divisions of the red nucleus in Macaca mulatta and Macaca fascicularis. Approximately 90% of the corticorubral projection is directed to the parvocellular division of the nucleus. Corticoparvocellular (CRp) neurons are pyramidally shaped, are smaller in size than corticospinal neurons, and are more numerous. They are found principally in sublamina Va of cytoarchitectonic areas 4 and 6, and in moderate quantities in sublamina Vb of posterior area 8 and area 5. In areas 4 and 6, the cells are grouped in clusters of three to 15 neurons each and are arranged in cellular bands of varying rostrocaudal thickness which course mediolaterally. With respect to functionally defined zones, CRp neurons are found throughout the supplementary motor area and the precentral motor cortex. In addition, they are found in parts of areas 5, 6, and 24 that project to these cortical motor areas, and that are thought to have "premotor" or movement-programming functions. The corticomagnocellular (CRm) projection arises principally from cells in sublamina Vb of the precentral arm and leg areas (area 4), and from adjacent parts of posterior area 6, CRm cells are pyramidally shaped, and their size distribution is bimodal, with peaks that correspond, respectively, to the modal diameters of CRp and of corticospinal neurons. These results and those of previous studies suggest that CRm neurons are involved principally in the control of hand and foot movements, with little effect on more proximal musculature. The massive CRp projection, however, is clearly part of a large cerebrocerebellar communication system, with motor and/or movement programming functions that have yet to be clearly defined.     

Prefrontal cortical projections to the hypothalamus in Macaque monkeys

The organization of projections from the macaque orbital and medial prefrontal cortex (OMPFC) to the hypothalamus and related regions of the diencephalon and midbrain was studied with retrograde and anterograde tracing techniques. Almost all of the prefrontal cortical projections to the hypothalamus arise from areas within the “medial prefrontal network,” as defined previously by Carmichael and Price ([1996] J. Comp. Neurol. 371:179–207). Outside of the OMPFC, only a few neurons in the temporal pole, anterior cingulate and insular cortex project to the hypothalamus. Axons from the OMPFC also innervate the basal forebrain, zona incerta, and ventral midbrain. Within the medial prefrontal network, different regions project to distinct parts of the hypothalamus. The medial wall areas 25 and 32 send the heaviest projections to the hypothalamus; axons from these areas are especially concentrated in the anterior hypothalamic area and the ventromedial hypothalamic nucleus. Orbital areas 13a, 12o, and Iai, which are related to the medial prefrontal network, selectively innervate the lateral hypothalamic area, especially its posterior part. The cellular regions of the paraventricular, supraoptic, suprachiasmatic, arcuate, and mammillary nuclei are conspicuously devoid of cortical axons, but many axons abut the borders of these nuclei and may contact dendrites that extend from them. Areas within the orbital prefrontal network on the posterior orbital surface and agranular insula send only weak projections to the posterior lateral hypothalamic area. The rostral orbital surface does not contribute to the cortico-hypothalamic projection. J. Comp. Neurol. 401:480–505, 1998. © 1998 Wiley-Liss, Inc.     

Banding of rubro-olivary terminations in the principal inferior olivary nucleus of the chimpanzee

An electrolytic lesion centered just dorsal to, and grazing the superior surface of, the rostral red nucleus (RNr) was produced stereotactically in a single chimpanzee. Perikarya of the ipsilateral RNr exhibited retrograde cell changes, demonstrating interruption of its efferent fibers. The degenerated rubro-olivary tract was followed in silver impregnated material to the ipsilateral compact part of the pedunculopontine nucleus, pontine reticular formation and inferior olivary complex. Within the inferior olivary complex, terminations were banded and restricted to the principal subnucleus.     

Calbindin and parvalbumin cells in monkey VPL thalamic nucleus: distribution, laminar cortical projections, and relations to spinothalamic terminations.

The ventral posterior lateral nucleus (VPL) of the monkey thalamus was investigated by histochemical staining for cytochrome oxidase (CO) activity and by immunocytochemical staining for the calcium-binding proteins parvalbumin and 28 kDa calbindin. Anterograde and retrograde tracing experiments were used to correlate patterns of differential distribution of CO activity and of parvalbumin and calbindin cells with the terminations of spinothalamic tract fibers and with the types of cells projecting differentially to superficial and deeper layers of primary somatosensory cortex (SI). VPL is composed of CO-rich and CO-weak compartments. Cells are generally smaller in the CO-weak compartment. Parvalbumin-immunoreactive cells and parvalbumin-immunoreactive medial lemniscal fiber terminations are confined to the CO-rich compartment. Calbindin-immunoreactive cells are found in both the CO-rich and CO-weak compartments. The CO-weak compartment, containing only calbindin cells, forms isolated zones throughout VPL and expands as a cap covering the posterior surface of the ventral posterior medial nucleus (VPM). Spinothalamic tract terminations tend to be concentrated in the CO-weak compartment, especially in the posterior cap. Other CO-weak, parvalbumin-negative, calbindin-positive nuclei, including the posterior, ventral posterior inferior, and anterior pulvinar and the small-celled matrix of VPM are also associated with concentrations of spinothalamic and caudal trigeminothalamic terminations. Parvalbumin cells are consistently larger than calbindin cells and are retrogradely labeled only after injections of tracers in middle and deep layers of SI. The smaller calbindin cells are the only cells retrogradely labeled after placement of retrograde tracers that primarily involve layer I of SI. The compartmental organization of VPL is similar to but less rigid than that previously reported in VPM. VPL and VPM relay cells projecting to different layers of SI cortex can be distinguished by differential immunoreactivity for the two calcium-binding proteins. The small-celled, CO-weak, calbindin-positive zones of VPL and VPM appear to form part of a wider system of smaller thalamic neurons unconstrained by traditional nuclear boundaries that are preferentially the targets of spinothalamic and caudal trigeminal inputs, and that may have preferential access to layer I of SI.     

红核在大脑皮质下行调控脊髓伤害感受性传递中的作用

以电刺激外周感受野诱发的大鼠脊髓背角WDR和NS神经元的晚串放电（C-反应）为指标,以串脉中刺激对侧大脑脚（CP）作为条件刺激,在C-反应受到明显抑制的神经元。分别观察了电解损毁红核（RN）和RN内注射兴奋性氨基酸的受体拮抗剂对刺激CP的下行抑制作用的影响。结果发现：损毁同侧RN后,刺激CP对C反应的抑制作用明显减弱,而损毁同侧RN背侧结构,对侧RN及假损毁RN均无此效应;RN内微量注射兴奋性氨基酸受体拮抗剂AP5和DNQX均可减弱刺激CP对C-反应的抑制。提示RN至少部分参与大脑皮质对脊髓伤害感受性传递的下行抑制作用。且以同侧RN为主;在与痛觉调制有关的皮质-RN通路中既有NMDA受体又有非NMDA受体的参与。     

Sources of cortical, hypothalamic and spinal serotoninergic projections: topical organization in the dorsal Raphe nucleus]

Distribution of primuline, fast blue, fluoro-gold and nuclear yellow-labelled monoamine-containing cells in periventricular gray and dorsolateral tegmentum (including locus coeruleus) was studied in the rat after injection of these fluorochromes into the frontal cortex, hypothalamus and spinal cord. Combination of monoamine fluorescence method and retrograde cell-labelling was used. Two big groups of serotonin-positive cells projecting into the upper thoracic spinal segments were found in dorsomedial zone of the dorsal raphe. Part of these units also had divergent axon projections to the frontal cortex. Such cellular arrangement allows a supposition that analgetic effects of dorsal raphe stimulation can be partially based on the direct participation of this structure in the descending control at the spinal level. Neurones, sources of cortical projections are intermingled with the cells projecting to the hypothalamus but some topical differentiation can be distinguished. Neurotransmitter and neuroregulatory roles of separate cortical and hypothalamic projections of serotonin-containing neurons of the dorsal raphe cells is discussed.     

Origins and terminations of descending noradrenergic projections to the spinal cord of monkey

This report describes the distribution of noradrenergic cells in the brainstem and the pattern of terminal varicosities in the spinal cord of monkey using the immunocytochemical localization of dopamine-beta-hydroxylase (DBH). Using two separate and equally reliable techniques, retrograde transport of the antibody to DBH and a double-labeling method, the cells of origin of noradrenergic fibers in the spinal cord have been identified. The results of these studies indicate that 79% of all noradrenergic cells with axons projecting to the spinal cord are located in the nucleus subcoeruleus and nucleus locus coeruleus. Other pontine noradrenergic cell groups contribute the remainder of the fibers to the cord. No medullary cells contribute to the noradrenergic innervation of the spinal cord.     

Development of ventral cochlear nucleus projections to the superior olivary complex in gerbil

The postnatal development of the projection from the ventral cochlear nucleus to the principal nuclei in the superior olivary complex in gerbil (Meriones unguiculatus) was studied in an age-graded series of pups ranging from 0 to 18 days old. Small crystals of 1, 1′-dioctadecyl3, 3, 3′, 3′-tetramethylindocarbocyanine perchlorate (DiI) were inserted into the ventral cochlear nucleus of aldehyde-fixed brains, and the labeled projections were examined with epifluorescence microscopy. Selected sections were photooxidized in a solution of diaminobenzidine and subsequently processed for electron microscopy to examine the development of labeled synapses in the target nuclei. Horseradish peroxidase was injected into the ventral cochlear nucleus of adult gerbils to assess the form and persistence of projections observed in the neonatal animals. In addition, electrophysiological responses to acoustic stimuli of single units in the adult auditory brainstem were analyzed to confirm the functionality of the novel projection from the ventral cochlear nucleus to the contralateral lateral superior olive. By the day of birth (PO), developing axons from the ventral cochlear nucleus have already established highly ordered pathways to the three primary nuclei of the superior olivary complex: the ipsilateral lateral superior olive, the contralateral medial nucleus of the trapezoid body, and at the lateral and medial dendrites of the ipsilateral and contralateral medial superior olive, respectively. Developing axons from the ventral cochlear nucleus that innervated the contralateral medial nucleus of the trapezoid body lacked the terminal morphology characteristic of the calyx of Held, but began to adopt a more characteristic form on P5. The mature calyx appeared around P14–16. Exuberant developmental projections to topographically inappropriate areas of the superior olivary complex were not observed at the postnatal ages studied. In addition to the projections of the ventral cochlear nucleus to the superior olivary complex described in other species, we observed the development and maintenance of a major direct projection from the ventral cochlear nucleus to the contralateral lateral superior olive. On PO, ventral cochlear nucleus axons decussate in the dorsal trapezoid body, form a plexus at the dorsal edge of the contralateral medial superior olive, and enter the ventrolateral limb of the contralateral lateral superior olive. Over the next 2 weeks, fascicles of fibers form on the hilar and ventral aspects of the ventrolateral limb. Fibers arising from these fascicles form converging, but nonoverlapping, arborizations within the ventrolateral limb at right angles to the curvature of the nucleus. The medial region was devoid of labeled axons. The direct innervation of the contralateral lateral superior olive was confirmed in the adult gerbil with anterograde horseradish peroxidase histochemistry and by the recording of excitatory responses in the innervated region to acoustic stimulation of the contralateral ear. © 1995 Wiley-Liss, Inc.     

Sensorimotor cortical projections to the primate cuneate nucleus

The organization of the corticocuneate pathway was investigated in monkeys by using the anterograde and retrograde axonal transport of either horseradish peroxidase (HRP) or wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Injection of either tracer into the precentral cortex (centered on area 4) results in heavy anterograde labeling in the tegmental region, which lies immediately ventrolateral to the cuneate nucleus, particularly at levels caudal to the obex. On the other hand, injections of the same tracers involving areas 3b, 1, and 2 cause anterograde labeling mainly within the core (pars rotunda of Ferraro and Barrera, '35, Arch. Neurol. Psychol. 33:262-75) of the cuneate nucleus. Anterograde labeling is also evident in the rostral parts of the cuneate nucleus, especially after injections involving areas 1 and 2. Injections restricted largely to area 3b cause anterograde labeling preferentially in the core of the cuneate nucleus. After injection of HRP or WGA-HRP into the dorsal medulla, retrogradely labeled neurons are present both in the pre- and postcentral gyrus, but their location depends upon the sites and extent of the injection site. When the tracer diffuses into the underlying tegmental area, many retrogradely labeled neurons appear in the precentral motor cortex, principally in area 4 although some of them also occur in area 6. With smaller injections, largely restricted within the cuneate nucleus, most labeled neurons are present in the postcentral gyrus, with the largest population in areas 1 and 2; a smaller number of small neurons in area 3b are best demonstrated with WGA-HRP; and area 3a contains the smallest complement of retrogradely labeled neurons. The data from these studies suggest a segregation of pre- and postcentral afferents in the ventral tegmental region and the cuneate nucleus, respectively. These findings pertaining to the corticocuneate projection in the monkey are discussed in relation to the parallelism between monkeys and cats possible physiological implications of the anatomical organization described, and conflicting evidence in the neurophysiological observations obtained, by earlier investigators, by antidromic and orthodromic activation of this pathway.     

The origins of descending spinal projections in lepidosirenid lungfishes

The origins of descending spinal projections in the lepidosirenid lungfishes were identified by retrograde transport of horseradish peroxidase (HRP) introduced into the rostral spinal cords of juvenile African (Protopterus annectans and Protopterus amphibians) and South American (Lepidosiren paradoxa) lungfishes. Standard HRP histochemistry revealed retrogradely labeled neurons in the nucleus of the medial longitudinal fasciculus, midbrain tegmentum, red nucleus, optic tectum, mesencephalic trigeminal nucleus, granule cell layer of the cerebellum, superior, middle, and inferior medullary reticular nuclei, magnocellular and descending octaval nuclei, region of the descending trigeminal tract, solitary complex, and the margins of the spinal gray matter anterior to the spinal HRP implant. A small number of retrogradely labeled neurons were also present in the ventral thalamus of Protopterus. A descending spinal projection from the forebrain was not evident in either genus of lepidosirenid lungfishes. The presence of projections to the spinal cord from the diencephalon, medial reticular formation of the midbrain and medulla, octaval (vestibular) nuclei, solitary complex, and probable nucleus of the descendin trigeminal tract in lungfishes and their overall similarity to comparable projections in other vertebrates suggest that these pathways are among those representative of the primitive pattern of descending spinal projections in vertebrates.     

Descending projections from the superior olivary complex to the cochlear nucleus of the cat

Subdivisions of the cochlear nuclear complex give rise to a number of discrete projections to certain cell groups of the superior olivary complex and also received substantial descending projections from the periolivary nuclei. In the present study, we sought to determine by means of retrograde transport of horseradish peroxidase (HRP), and anterograde transport of radiolabeled protein, if the periolivary nuclei give rise to discrete projections to the various subdivisions of the cochlear nuclear complex. Following medium to large injections of HRP into the cochlear nucleus, irrespective of location, labeled cells were found in all periolivary nuclei bilaterally. In every case more than 40% of the labeled cells were found in the lateral nucleus of the trapezoid body on the same side and the ventral nucleus of the trapezoid body of both sides. Other periolivary nuclei contributing more than 5% of the total number of cells in individual cases were the contralateral lateral nucleus of the trapezoid body and the ipsilateral anterolateral and dorsal periolivary nuclei. Injections of tritiated leucine into periolivary nuclei gave rise to axonal labeling to the trapezoid body and the dorsal acoustic stria, usually bilaterally, and to terminal labeling that was widely distributed within the cochlear nuclear complex. In several cases with small injections, particularly in the lateral nucleus of the trapezoid body, the projections from the periolivary nuclei to the anteroventral and dorsal cochlear nuclei connected areas described as having similar best-frequency representation. The autoradiographic data corroborated the main results from the HRP experiments and provided additional information permitting these conclusions: the projections from the periolivary nuclei to the cochlear nuclear complex are organized tonotopically, at least in part; each periolivary nucleus (and perhaps individual cells), projects widely throughout the cochlear nuclear complex; the pattern of termination of projections from different periolivary nuclei to a given region of the cochlear nuclear complex are similar, as seen in autoradiograms, and the lateral and dorsal periolivary nuclei project mainly ipsilaterally, while the medial periolivary nuclei project bilaterally with a contralateral bias. The magnitude of these projections and their widespread distribution within the cochlear nuclear complex would suggest an important role for the descending projections in the normal functioning of the cochlear nucleus.     

Cerebellar projections to the red nucleus of the cat

The organization of cerebello-rubral projections in the cat was studied after injection of Diamidino yellow and/or horseradish peroxidase into the red nucleus (RN). The nucleus interpositus posterior projects to the rostral RN and the nucleus interpositus anterior to the caudal RN. In each case only sparse retrograde labeling was observed in the nucleus lateralis. These projection zones do not correspond with the organization of rubrospinal projections.     

The red nucleus activity in rats deprived of the inferior olivary complex

The long-term effects of the inferior olive destruction on the red nucleus activity, were studied in the rat following injection of 3-acetylpyridine. As soon as the olivary activity was suppressed, the discharge of the rubral units drastically decreased. Then, they progressively recovered the control frequency during the first month, although a normal rubral activity was not restored up to 8 months. The hypothesis is advanced that the olivocerebellar system is essential to shape the activity of the rubrospinal pathway.     

Edinger-Westphal nucleus: cholecystokinin immunocytochemistry and projections to spinal cord and trigeminal nucleus in the cat

Immunocytochemical methods were used to determine the distribution of cells with cholecystokinin-like immunoreactivity (CCK-LI) in the cat Edinger-Westphal complex (EW). Numerous cells with CCK-LI are found throughout the length of EW. The distribution and frequency of such cells are similar to the pattern of EW neurons that show substance P-like immunoreactivity (SP-LI). Companion retrograde transport experiments reveal that EW neurons which project to spinal cord or the region of the caudal trigeminal nucleus are found throughout the length of EW, and that some EW neurons which project to spinal cord also show CCK-LI.     

Prefrontal cortical projections to longitudinal columns in the midbrain periaqueductal gray in Macaque monkeys

The origin and termination of prefrontal cortical projections to the periaqueductal gray (PAG) were defined with retrograde axonal tracers injected into the PAG and anterograde axonal tracers injected into the prefrontal cortex (PFC). The retrograde tracer experiments demonstrate projections to the PAG that arise primarily from the medial prefrontal areas 25, 32, and 10m, anterior cingulate, and dorsomedial areas 24b and 9, select orbital areas 14c, 13a, Iai, 12o, and caudal 12l, and ventrolateral area 6v. Only scattered cells were retrogradely labeled in other areas in the PFC. Caudal to the PFC, projections to the PAG also arise from the posterior cingulate cortex, the dorsal dysgranular, and granular parts of the temporal polar cortex, the ventral insula, and the dorsal bank of the superior temporal sulcus. Cells were also labeled in subcortical structures, including the central nucleus and ventrolateral part of the basal nucleus of the amygdala. The anterograde tracer experiments indicate that projections from distinct cortical areas terminate primarily in individual longitudinal PAG columns. The projections from medial prefrontal areas 10m, 25, and 32 end predominantly in the dorsolateral columns, bilaterally. Fibers from orbital areas 13a, Iai, 12o, and caudal 12l terminate primarily in the ventrolateral column, whereas fibers from dorsomedial areas 9 and 24b terminate mainly in the lateral column. The PFC areas that project to the PAG include most of the areas previously defined as the “medial prefrontal network.” The areas that comprise this network represent a visceromotor system, distinct from the sensory related “orbital network.” J. Comp. Neurol. 401:455–479, 1998. © 1998 Wiley-Liss, Inc.     

GABA- and glycine-immunoreactive projections from the superior olivary complex to the cochlear nucleus in guinea pig

Retrograde transport of horseradish peroxidase was combined with immunocytochemistry to identify the origins of potential γ-aminobutyric acid (GABA) -ergic and glycinergic inputs to different subdivisions of the cochlear nucleus. Projection neurons in the inferior colliculus, superior olivary complex, and contralateral cochlear nucleus were examined, but only those from the superior olivary complex contained significant numbers of GABA- or glycine-immunoreactive neurons. The majority of these were in periolivary nuclei ipsilaterally, with a sizeable contribution from the contralateral ventral nucleus of the trapezoid body. Overall, 80% of olivary neurons projecting to the cochlear nucleus were immunoreactive for GABA, glycine, or both. Most glycine-immunoreactive projection neurons were located ipsilaterally, in the lateral and ventral nuclei of the trapezoid body and the dorsal periolivary nucleus. This suggests that glycine is the predominant neurotransmitter used by ipsilateral olivary projections. Most GABA-immunoreactive cells were located bilaterally in the ventral nuclei of the trapezoid body. The contralateral olivary projection was primarily GABA-immunoreactive and provided almost half the GABA-immunoreactive projections to the cochlear nucleus. This suggests that GABA is the predominant neurotransmitter used by contralateral olivary projections. The present results suggest that the superior olivary complex is the most important extrinsic source of inhibitory inputs to the cochlear nucleus. Individual periolivary nuclei differ in the strength and the transmitter content of their projections to the cochlear nucleus and may perform different roles in acoustic processing in the cochlear nucleus. J. Comp. Neurol. 381:500-512, 1997. © 1997 Wiley-Liss, Inc.