Descending projections to the mammillary nuclei in the rat, as studied by retrograde and anterograde transport of wheat germ agglutinin-horseradish peroxidase

The cells of origin and projection fields of the descending afferents to the mammillary nuclei were studied in the rat with retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase. The subiculum projects bilaterally to the entire medial mammillary nucleus (MM) in a topographic fashion along the two axes: 1) the proximal part of the subiculum along the presubiculo-CA1 axis projects to the caudal and lateral regions of the MM whereas the more distal part of the subiculum projects to the medial region; 2) the septal part of the subiculum projects to the caudodorsal region of the MM whereas the more temporal part projects progressively to the more rostroventral regions. The ventral subiculum also projects ipsilaterally to the ventral and lateral margin of the lateral mammillary nucleus (LM). The presubiculum projects bilaterally to the dorsolateral region of the pars posterior of the MM and ipsilaterally to the LM. The infra-limbic cortex projects bilaterally to the rostrodorsal region of the MM, whereas the retrosplenial cortex (areas 29a and 29b) projects bilaterally to the medial region at the midrostrocaudal and middorsoventral levels of the MM. The nucleus of the diagonal band projects bilaterally to the caudomedial region of the MM, whereas the lateral septal nucleus projects bilaterally to the pars mediana and the mammillary fiber capsule. A part of the anterior hypothalamic area ventromedial to the fornix projects predominantly ipsilaterally to the rostroventral part of the MM, whereas other basal forebrain regions such as the bed nucleus of the stria terminalis, the medial preoptic and anterior hypothalamic areas, and the area of the tuber cinereum send fibers predominantly ipsilaterally to the mammillary fiber capsule. The results reveal a complex organization of the descending projections to the mammillary nuclei, which may reflect the complex functions of these nuclei within the limbic circuitry.     

Postnatal maturation in the cochlea of the cat

At birth, the cochlea of the cat, though generally developed, is still immature. Maturation of the organ of Corti begins at the base and gradually reaches the apex. In two weeks the process is complete. The most significant morphological criteria of the epithelial maturation are the formation of the tunnel of Corti and of the space of Nuel, the lengthening of the outer hair cells and the freeing of the internal spiral sulcus. On the third day after birth, the appearance of these criteria at the level of the first coil of the lamina spiralis coincides with the general physiological awakening of the auditory systems, as testified by the recording of evoked potentials from the cerebral cortex. Since such responses can be provoked by electrical stimulation of the nerve from birth onwards, the maturation of the organ of Corti appears to be the final stage in the development of the auditory system.     

The callosal connexions of the primary somatic sensory cortex in the monkey

The callosal connexions of the primary somatic sensory cortex, SI, of the monkey have been studied with axonal degeneration methods after the placement of lesions of varying size in the cortex of one hemisphere and after section of the corpus callosum. For the correlation of the distribution of the degeneration with the cytoarchitectonic subdivisions of SI and with their boundaries, planar reconstructions of the extents of the subdivisions and of area 5 were made. The extent of area 5 is surprisingly large, being about the same as SI, and area 3a can be recognized as a distinct subdivision along the entire medio-lateral extent of SI. The callosal fibres end in narrow, irregular bands aligned in the medio-lateral dimension and there are accentuations at the boundaries of the cytoarchitectural subdivisions. In the representations of the trunk and face, the bands of degeneration are present across the entire antero-posterior extent of SI and with increases at the boundaries, while in the limb regions the degeneration becomes restricted to the boundaries. It is suggested that the callosal connexions of the somatic sensory cortex, like those in the visual and auditory areas, are connecting those parts of the cortex in the two hemispheres that are concurrently activated by a peripheral stimulus. The parts of SI that are devoid of callosal connexions are related to the distal limbs. The callosal connexions are homo- and heterotopical; an architectonic subdivision within the callosally connected regions projects to the same and other architectonic subdivisions at the same medio-lateral level in the opposite hemisphere; the cortex containing the representation of the caudal trunk near the post-central dimple is connected with the same region in the other hemisphere and with that of the separate representation of the caudal trunk in the posterior part of the cingulate sulcus, while the representation of the occipital region at the post-central dimple is connected both with the homotopical site in the other hemisphere and with the other representation of this part of the periphery at the level of the lower end of the intraparietal sulcus.     

The somatotopic organization of forelimb cutaneous nerves in the brachial dorsal horn: an anatomical study in the cat

The projection of forelimb cutaneous nerves to the brachial dorsal horn was studied in the cat by the transganglionic transport method. The results demonstrate a precise somatotopic termination pattern. Afferent nerves from the paw occupy the largest area, with the palm represented most medially in the dorsal horn, followed progressively more laterally by the representations for the palmar and dorsal surfaces of the digits and the dorsum of the paw. The digits are represented in a longitudinal sequence, with the first digit in the caudal part of C6 and the fifth in the caudal part of C8. The projections of the wrist and arm are split, with the line of discontinuity located along the ventral surface of the limb, so that the radial side is represented rostral to the paw and the ulnar side caudal to the paw, with the dorsal surface of the arm represented lateral to the paw. Nerves innervating the skin of the back project to the lateralmost part of the dorsal horn. The degree of overlap or separation of the terminal fields of the nerves along the mediolateral axis of the dorsal horn seems to correspond to the degree of overlap or separation of the peripheral innervation fields. However, along the rostrocaudal axis there appears to be an overlap for which there is no counterpart peripherally.     

Centrifugal influence on olfactory bulb activity in the rabbit

(1) Regions which exert centrifugal influences on the olfactory bulb activity were studied by applying systematic stimulation to various areas of the ipsilateral telencephalon in the rabbit. By delivering electric stimuli to the anterior commissure (AC), the deep lying structures in the projection areas of the lateral olfactory tract (LOT) and the medial forebrain bundle situated between the lateral hypothalamic area and the lateral preoptic area, negative field potentials were evoked in the granule cell layer (GCL) of the bulb. (2) Intracellular recordings from the mitral cells and the GCL neurons in the olfactory bulb were performed in order to clarify the modes of the centrifugal influences on the olfactory bulb neurons. (3) EPSPs were recorded in the GCL neurons by stimulation of the deep-lying structure of the prepiriform cortex as well as by stimulation of the AC. The onset time and duration of the EPSPs corresponded well to those of the negative field potentials in the GCL. Thus, it was suggested that these negative potentials were caused by the EPSPs of the number of granule cells. (4) In almost all of the mitral cells, IPSPs were recorded by stimulation of the AC and the deep-lying structures of the LOT projection areas. The onsets of the IPSPs were found with delays of several milliseconds from those of the negative field potentials in the GCL. (5) It was postulated that the excitation of the centrifugal system mainly exerts a depressive influence on the activity of the mitral cell, and that the GCL neuron (presumably the granule cell) seems to be an inhibitory interneuron interpolated between the extrinsic fibers from the telencephalon and the mitral cell.     

The vestibular nuclei in the domestic hen (Gallus domesticus): VI. Afferents from the cerebellum

Following horseradish peroxidase (HRP) injections in the superior, in the Deiters', in the medial, and in the descending vestibular nuclei in the hen, labeled cells are found in lateral longitudinal zones in the ipsilateral cerebellar cortex, most numerously in the anterior lobe, the nodulus, the uvula, and the auricle. Furthermore, labeled cells are found bilaterally in the ventral parts of the medial and intermediate cerebellar nuclei. Lesions in the cerebellar cortex of the anterior lobe and in anterior parts of the posterior lobe result in terminal degeneration, mainly in the nucleus Deiters dorsalis, but also scantily, in peripheral regions of the superior nucleus, the nucleus Deiters ventralis, the ventrolateral part of the medial nucleus and, mainly medially, in the descending nucleus. Lesions in the posterior part of the uvula, in the nodulus, and in the auricle result in much denser degeneration, most heavily affecting the nucleus Deiters dorsalis, but also affecting peripheral regions of the superior nucleus, the nucleus Deiters ventralis, the entire descending and medial nuclei, and the tangential nucleus. Lesions in the medial cerebellar nucleus result in degeneration bilaterally in the vestibular complex, most heavily affecting the nucleus Deiters ventralis and cell group B, but also affecting peripheral regions of the superior nucleus, the medial nucleus—mainly in dorsomedial regions, lateral and caudal parts of the descending nucleus and, very scantily, in the nucleus Deiters dorsalis. The findings are discussed in the light of the data concerning the organization of the cerebellovestibular projections in mammals and the known connections of the vestibular nuclei in birds.     

Representation of the cecum in the lateral dorsal motor nucleus of the vagus nerve and commissural subnucleus of the nucleus tractus solitarii in rat.

Motor fibers of the accessory celiac and celiac vagal branches are derived from the lateral columns of the dorsal motor nucleus of the vagus nerve. These branches also contain sensory fibers that terminate within the nucleus of the tractus solitarii. This study traces the innervation of the intestines by using the tracer cholera toxin-horseradish peroxidase. In 53 rats, the tracer was injected into either the stomach, duodenum, jejunum, terminal ileum, cecum, or ascending colon. With all cecal injections, prominent retrograde labeling of cell bodies occurred bilaterally in the lateral columns of the dorsal motor nucleus of the vagus nerve above, at, and below the level of the area postrema. Dendrites of laterally positioned neurons projected medially and rostrocaudally within the dorsal motor nucleus of the vagus nerve and dorsomedially into both the medial subnucleus and parts of the commissural subnucleus of the nucleus of the tractus solitarii. Sensory terminal labeling occurred in the dorsolateral commissural subnucleus at the level of the rostral area postrema and the medial commissural subnucleus caudal to the area postrema. Additionally, there was sensory terminal labeling within a small confined area of the dorsomedial zone of the nucleus of the tractus solitarii immediately adjacent to the fourth ventricle at a level just anterior to the area postrema. Stomach injections labeled motoneurons of the medial column of the entire rostrocaudal extent of the dorsal motor nucleus of the vagus nerve and a sensory terminal field primarily in the subnucleus gelatinosus, with less intense labeling extending caudally into the medial and ventral commissural subnuclei. Dendrites of gastric motoneurons project rostrocaudally and mediolaterally within the dorsal motor nucleus of the vagus nerve and dorsolaterally within the nucleus of the tractus solitarii. They are most pronounced at the level of the rostral area postrema where many dendrites course dorsolaterally terminating primarily within the subnucleus gelatinosus. Injections of the duodenum labeled a small number of the cells within the medial aspects of the dorsal motor nucleus of the vagus nerve. Jejunal, ileal, and ascending colon injections labeled cells sparsely within the lateral aspects of the dorsal motor nucleus of the vagus nerve bilaterally. No afferent terminal labeling was evident after injection of these areas of the bowel.(ABSTRACT TRUNCATED AT 400 WORDS)     

Corticocortical connections of frontal oculomotor areas in the cat

The corticocortical connections of the frontal 'oculomotor' areas related to eye movements of the cat were studied using the retrograde horseradish peroxidase (HRP) tracing method combined with electrophysiological techniques. The following results were obtained. (1) The medial wall of the hemisphere under the cruciate sulcus (CRU), where contralateral conjugate eye deviation was elicited, received fibers from the medial bank of the presylvian sulcus (PRE). The fundus of the coronal sulcus (COR), where monocular movement of the contralateral eye was evoked, received fibers from the lateral bank of the PRE. (2) All the frontal oculomotor areas, the medial wall of the hemisphere under the CRU, the fundus of the COR, and both banks of the PRE, received fibers from the ipsilateral ventral bank of the anterior ectosylvian sulcus (AES). (3) The ventral bank of the AES received fibers from the caudal part of the lateral suprasylvian visual areas. On the basis of the fiber connections, the frontal oculomotor areas can be subdivided into a 'medial' area, the medial wall of the hemisphere under the CRU and the medial bank of the PRE, and a 'lateral' area, the lateral bank of the PRE and the fundus of the COR. Moreover, we found evidence of fiber projections from the ventral bank of the AES to the frontal oculomotor areas that were physiologically identified.     

Die stereotaktische Orientierung im menschlichen Hirn an Hand röntgenologischer Befunde

All attempts to reconstruct the topography of the brain in the living from studies of animal material are handicapped by technical difficulties. The best method is to compare exact X-ray pictures, which have been taken under stereotactic conditions. From a large collection of such X-rays the authors have composed contours of the internal table of the skull and of the ventricles, which best match the brains, selected for the Schaltenbrand-Bailey sterotactic atlas. For practical purposes these contours were combined with the transparent overlays for the nomenclature and the border lines of the different parts of the basal ganglia, which have been used in the myelin sections part of the atlas. A comparison of our sagittal series with the new X-ray findings shows, that the sagittal schemata of the atlas represent an extreme variation in the position of the Meynert axis and of the contours of the 4th ventricle. We have chosen a new axis system for the hindbrain, which corresponds to the average of our brains in constructing a new set of typical overlays for the atlas. The contour of the posterior fossa had to be completed. An independent axis system dor the structures of the 4th ventricle was developed, consisting of the base of the 4th ventricle, and a tangent, to the upper contour of the pons. In sterotactic procedures the axis systems for the forebrain and the hindbrain should be used independently. The results obtained are the basis for a new series of lantern slides which can be projected against the X-ray pictures with the Würzburg stereotactic equipment. In the course of this investigation we discovered a source of error. When air enters the puncture hole of the dura, the brain may sink back, so with the patient lying on his back, all structures may shift a few millimeters towards the occipital region. When the patient is lying on his side, as during an approach to the amygdala through the planum temporale, the ventricular system may collapse, so that almost no air is visible in the ventricles and the 3rd ventricle may appear to be in the lower hemisphere, the dislocation being more than 5-8 mm. But filling the ventricle with air through the ventricular catheter is sufficient to blow up the brain and to restore the normal topography.     

桥小脑角区神经内镜下解剖学研究及临床应用

目的通过神经内镜下桥小脑区的解剖,为内镜辅助下该区域病变的手术治疗提供解剖学支持,并探讨其临床应用价值。方法在8具福尔马林固定的成人尸头标本和4具新鲜成人尸头标本上,交替使用神经内镜和手术用显微镜,在模拟手术的条件下进行桥小脑角区的窥镜下解剖学研究,并实际应用于临床。结果内镜经小脑外侧间隙可顺利到达桥小脑角区和脑干前方,可清晰显示V～XI颅神经及其附近走行的血管,手术中可明显改善深部术野的照明效果和显微解剖结构的识别,减少对小脑和脑干的牵拉,提高手术的安全性,减少并发症的发生。结论神经内镜在颅内实质性肿瘤的切除术中的应用可弥补手术显微镜的不足,对显微外科手术起到重要的辅助作用。     

Rubrobulbar projections in the rabbit. A light and electron microscopic study

The crossed rubrobulbar fibers coursing in association with the classical rubrospinal tract in the rabbit were investigated by means of the Nauta and the Fink-Heimer methods. The synaptic organization within the terminal areas of the rubrobulbar fibers were also studied electron microscopically. The crossed rubrobulbar fibers are distributed to the ventral portion of the reticular area intercalated between the motor and the main sensory nuclei of the trigeminal nerve, to the ventrolateral part of the lateral parvocellular reticular formation, the dorsal region of the facial nucleus, the subtrigeminal portion of the lateral reticular nucleus, and the rostrolateral part of the main portion of the lateral reticular nucleus. Small to medium-sized, electron-dense, degenerated synaptic knobs were observed in the dorsal region of the facial nucleus and in the rostrodorsolateral part of the lateral reticular nucleus. All of the synaptic vesicles contained in the degenerated synaptic bags were spherical. Almost all of the degenerated synaptic terminals were in contact with dendritic profiles. Sporadic electron-dense synaptic knobs contacting the soma of nerve cells were encountered only in the dorsal aspect of the facial nucleus.     

Projections from the amygdaloid complex to the piriform cortex: A PHA-L study in the rat

Projections from the amygdala to the piriform cortex are proposed to provide a pathway via which the emotional system can modulate the processing of olfactory information as well as mediate the spread of seizure activity in epilepsy. To understand the details of the distribution and topography of these projections, we injected the anterograde tracer Phaseolus vulgaris-leucoagglutinin into different nuclear divisions of the amygdaloid complex in 101 rats and analyzed the distribution and density of projections in immunohistochemically processed preparations. The heaviest projections from the amygdala to the piriform cortex originated in the medial division of the lateral nucleus, the periamygdaloid and sulcal subfields of the periamygdaloid cortex, and the posterior cortical nucleus. The heaviest terminal labeling was observed in layers Ib and III of the medial aspect of the posterior piriform cortex. Lighter projections to the posterior piriform cortex originated in the dorsolateral division of the lateral nucleus, the magnocellular and parvicellular divisions of the basal and accessory basal nuclei, and the anterior cortical nucleus. The projections to the anterior piriform cortex were light and originated in the dorsolateral and medial divisions of the lateral nucleus, the magnocellular division of the basal and accessory basal nuclei, the anterior and posterior cortical nuclei, and the periamygdaloid subfield of the periamygdaloid cortex. The results indicate that only selective amygdaloid nuclei or their subdivisions project to the piriform cortex. In addition, substantial projections from several amygdaloid nuclei converge in the medial aspect of the posterior piriform cortex. Via these projections, the amygdaloid complex can modulate the processing of olfactory information in the piriform cortex. In pathologic conditions such as epilepsy, these connections might provide pathways for the spread of seizure activity from the amygdala to extra-amygdaloid regions.     

Amygdaloid projections to the frontal cortex and the striatum in the rat.

Projections from the basolateral nucleus of the amygdala (BLA) to the frontal cortex and the striatum were studied by using Phaseolus vulgaris-leucoagglutinin (PHA-L) anterograde tracing technique in the rat. PHA-L injections into the rostral part of the BLA resulted in a dense labeling of fibers with boutons in the dorsal bank of the rhinal fissure and in the lateral and the medial agranular cortex. PHA-L injections into the caudal part of the BLA produced a dense labeling of fibers in the medial surface of the frontal cortex. In most of the cortical regions, labeled fibers were predominantly distributed in two bands: one in the deep part of layers I and II and the other, heavier band, in layers V and VI. PHA-L injections into the rostral BLA resulted in a dense labeling of fibers with boutons in the olfactory tubercle, the rostral and caudolateral portion of the nucleus accumbens, and a large region of the caudate-putamen. The labeled area of the caudate-putamen included the rostroventral area, the central area, and the area caudal to the anterior commissure and dorsal and lateral to the globus pallidus. PHA-L injections into the caudal BLA produced fiber labeling in the most rostromedial area of the caudate-putamen facing the lateral ventricle, the medial portion of the nucleus accumbens, and the lateral septum. In the rostroventral striatum, PHA-L-labeled fibers selectively innervated the matrix compartment that contains abundant somatostatin-immunoreactive fibers. Compartmental segregation was less clear in the caudodorsolateral caudate-putamen and in the nucleus accumbens. Electron microscopy revealed that PHA-L-labeled boutons in the striatum contained abundant, small, round vesicles. These boutons formed asymmetrical synapses with dendritic spines of striatal neurons.     

The efferent connections of the anterior hypothalamic area of the rat, cat and monkey.

The general morphology and topographic relations of the anterior hypothalamic area (AHA) in the rat, cat and squirrel monkey have been described, and its efferent connections analyzed autoradiographically, after small injections of 3H-labeled amino acids into, or around, the area. In all three species the AHA is rather poorly separated from the surrounding preoptic and hypothalamic areas and nuclei but shows three distinct cellular condensations, located rostrally, centrally, and posterodorsally. Closely associated with the AHA are the retrochiasmatic area, the anterior periventricular nucleus and the scattered neurons usually referred to as the accessory supraoptic nucleus. The AHA has primarily short connections to the adjoining medial preoptic area, the lateral hypothalamic area, the periventricular nucleus, the dorsomedial nucleus, and to the "capsule" of the ventromedial nucleus. However, it also has certain more distant projections, rostrally to a narrow zone centered in the ventral part of the lateral septal nucleus, and caudally to the dorsal premammillary nuclei, the posterior hypothalamic area and the central gray. There is some evidence to suggest that the various subdivisions of the AHA have different efferent connections. Thus the posterodorsal cell condensation appears to give rise to the bilateral projection to the dorsal premammillary nuclei, while the projections to the septum, the posterior hypothalamic area and the central gray seem to have their origin in the central condensation. Similarly, the retrochiasmatic area sends its efferents through the ventral supraoptic commissure to the amygdala, the anterior periventricular nucleus contributes to the periventricular fiber system and to the external lamina of the median eminence, and the accessory supraoptic neurons project to the internal lamina of the median eminence.     

Connections of the subthalamic nucleus with ventral striatopallidal parts of the basal ganglia in the rat

The present study was undertaken to establish the precise anatomical relationship of the subthalamic nucleus (STh) with limbic lobe-afferented parts of the basal ganglia in the rat. The anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L), injected in the STh, the globus pallidus, the ventral pallidum, the ventral striatum, and the parafascicular thalamic nucleus, and the retrograde tracers Fluoro-Gold (FG) and cholera toxin B (CTb), injected in the globus pallidus, the ventral pallidum, the ventral striatum, and the ventral mesencephalon, were used for this purpose. The results of these tracing experiments confirm the general notion of reciprocal connections between the STh and pallidal areas. Thus the dorsomedial part of the STh is connected with the subcommisural ventral pallidum, whereas a more ventral and lateral part of the medial STh is related to the medial globus pallidus. The lateral hypothalamic area, directly adjacent to the STh, containing neurons with a morphology quite similar to those in the STh, projects to parts of the ventral pallidum related to the olfactory tubercle. The reciprocal projection from this pallidal area to subthalamic regions appears to be very sparse. The medial STh sends strong projections to the medial part of the entopeduncular nucleus and the adjacent lateral hypothalamic area. Sparser projections from the medial STh reach the rostral and medial part of the caudate-putamen and the nucleus accumbens. The nucleus accumbens sends a very sparse projection back to the medial STh. The projections of the medial STh to the ventral mesencephalon appear also to be topographically organized. The lateral hypothalamus and a few cells in the most medial part of the STh project to the ventral tegmental area, whereas progressively more lateral parts of the ventral mesencephalon, in particular the substantia nigra, receive input from successively more lateral and caudal parts of the STh. In addition, a number of STh fibers reach the midbrain extrapyramidal area. The lateral part of the parafascicular thalamic nucleus projects to the lateral part of the STh, whereas parafascicular neurons medial to the fasciculus retroflexus project to the dorsomedial portion of the STh. The medial part of the STh and the adjacent lateral hypothalamus are intimately connected with limbic parts of the basal ganglia in a way similar and parallel to the connections of the lateral STh with motor-related parts of the basal ganglia. These findings suggest a role for the STh in nonmotor functions of the basal ganglia.     

Alpha-melanocyte stimulating hormone immunoreactivity in the brain of the cichlid fish Oreochromis mossambicus

This study reports the distribution of a pro-opiomelanocortin-derived neuropeptide α–MSH in the brain of the cichlid fish Oreochromis mossambicus. α–MSH-ir fibres were found in the granule cell layer of the olfactory bulb, the medial olfactory tract, the pallium and the subpallium, whereas in the preoptic area of the telencephalon, few large α–MSH-ir perikarya along with extensively labeled fibres were observed close to the ventricular border. Dense network of α–MSH-ir fibres were seen in the hypothalamic areas such as the nucleus preopticus pars magnocellularis, the nucleus preopticus pars parvocellularis, the suprachiasmatic nucleus, the nucleus anterior tuberis, the paraventricular organ, the subdivisions of the nucleus recessus lateralis and the nucleus recessus posterioris. In the nucleus lateralis pars medialis, some α–MSH-ir perikarya and fibres were found along the ventricular margin. In the diencephalon, numerous α–MSH-ir fibres were detected in the nucleus posterior tuberis, the nucleus of the fasciculus longitudinalis medialis and the nucleus preglomerulosus medialis, whereas in the mesencephalon, α–MSH-ir fibres were located in the optic tectum, the torus semicircularis and the tegmentum. In the rhombencephalon, α–MSH-ir fibres were confined to the medial octavolateralis nucleus and the descending octaval nucleus. In the pituitary gland, densely packed α–MSH-ir cells were observed in the pars intermedia region. The widespread distribution of α–MSH-immunoreactivity throughout the brain and the pituitary gland suggests a role for α–MSH peptide in regulation of several neuroendocrine and sensorimotor functions as well as darkening of pigmentation in the tilapia.     

Two distinct strio-nigral substance P pathways in the rat: An experimental immunohistochemical study

Re-examination of the strio-nigral substance P (SP) tract by means of an experimental immunohistochemical method in the rats demonstrated the presence of two distinct pathways from the nucleus caudatus putamen (CP) to the substantia nigra (SN). Destruction of the posterior portion of the CP resulted in the disappearance of SP-positive fibers in the SN pars lateralis but not in the SN pars compacta or reticulata. On the other hand, destruction of the ventrolateral portion of the anterior portion of the CP caused the disappearance of SP-positive fibers in the SN pars compacta and pars reticulata but not in the SN pars lateralis. In addition, destruction of the dorsal portion of the anterior portion of the CP, where 3-6 cell islets of SP-positive cells are located, failed to decrease SP-positive fibers in any of the subdivisions of the SN. These findings strongly suggest that SP-positive neurons in the posterior portion of the CP project to the SN pars lateralis (posterior strio-nigral SP tract), SP-positive cells in the lateroventral part of the anterior portion of the CP extend to the SN pars compacta and pars reticulata, but SP-positive cells in the dorsal part of the anterior portion of the CP do not innervate the SN.     

Corticonuclear and corticovestibular projections from the uvula in the albino rat: differential projections from sublobuli of the uvula

The organization of the corticonuclear and corticovestibular projections from the uvula was investigated in the albino rat by an autoradiographic method. The corticonuclear fibers from sublobule a of the uvula terminated in the caudoventral part of the medial cerebellar nucleus, and the caudomedial part of the posterior interpositus nucleus with mediolateral topography. The medial and lateral portions of the sublobule projected to the medial cerebellar and posterior interpositus nuclei, respectively. The corticovestibular fibers from sublobule a terminated in the dorsal and rostral parts of the superior vestibular nucleus, the dorsal part of the lateral vestibular nucleus, and the caudomedial part of the spinal vestibular nucleus. However, the corticonuclear fibers from sublobuli b and c of the uvula terminated additionally in the ventromedial part of the lateral cerebellar nucleus, while the corticovestibular fibers from these sublobuli terminated additionally in the subnucleus y of the vestibular complex, with probable termination in the medial vestibular nucleus. The cortical region which sent efferent projections to the ventromedial part of the lateral cerebellar nucleus and the subnucleus y was located laterally in sublobuli b and c of the uvula. These differential projection patterns from the dorsal and ventral sublobuli suggest the difference of the functional correlates between the sublobuli in the uvula.     

Organization of cortical, basal forebrain, and hypothalamic afferents to the parabrachial nucleus in the rat.

In a previous study (Herbert et al., J. Comp. Neurol. [1990];293:540-580), we demonstrated that the ascending afferent projections from the medulla to the parabrachial nucleus (PB) mark out functionally specific terminal domains within the PB. In this study, we examine the organization of the forebrain afferents to the PB. The PB was found to receive afferents from the infralimbic, the lateral prefrontal, and the insular cortical areas; the dorsomedial, the ventromedial, the median preoptic, and the paraventricular hypothalamic nuclei; the dorsal, the retrochiasmatic, and the lateral hypothalamic areas; the central nucleus of the amygdala; the substantia innominata; and the bed nucleus of the stria terminalis. In general, forebrain areas tend to innervate the same PB subnuclei from which they receive their input. Three major patterns of afferent termination were noted in the PB; these corresponded to the three primary sources of forebrain input to the PB: the cerebral cortex, the hypothalamus, and the basal forebrain. Hypothalamic afferents innervate predominantly rostral portions of the PB, particularly the central lateral and dorsal lateral subnuclei. The basal forebrain projection to the PB ends densely in the external lateral and waist subnuclei. Cortical afferents terminate most heavily in the caudal half of the PB, particularly in the ventral lateral and medial subnuclei. In addition, considerable topography organization was found within the individual projections. For example, tuberal lateral hypothalamic neurons project heavily to the central lateral subnucleus and lightly to the waist area; in contrast, caudal lateral hypothalamic neurons send a moderately heavy projection to both the central lateral and waist subnuclei. Our results show that the forebrain afferents of the PB are topographically organized. These topographical differences may provide a substrate for the diversity of visceral functions associated with the PB.