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PubMed1981

Glossopharyngeal and vagal afferent projections to the brain stem of the cat: a horseradish peroxidase study.

Brain stem projections of the glossopharyngeal and vagus nerves in the cat were studied using the anterograde transport of horseradish peroxidase (HRP). Crystalline HRP was applied to the proximal cut ends of the nerves for a period of 4-10.5 h, and after a survival time of 24-120 h, transverse and horizontal sections of the brain stem were processed according to the tetramethylbenzidine method. Labeled fibers from both nerves were found to project bilaterally to the solitary complex, and ipsilaterally to the ventral region of the external cuneate nucleus and to the medial region of the nucleus praepositus hypoglossi, just dorsolateral to the medial longitudinal fasciculus. Within the solitary complex terminal labeling was found in the parvocellular, ventrolateral, lateral, medial and commissural solitary nuclei. Exclusive glossopharyngeal nerve projections were found ipsilaterally in the rostral dorsal motor nucleus of the vagus, the ventrolateral portion of the medial cuneate nucleus, the dorsal part of the nuclei caudalis and interpolaris of the trigeminal complex, the nuclei insulae cuneati lateralis, and the dorsolateral aspect of the nucleus medullae oblongata centralis. Finally, in the area postrema a bilateral projection of vagal and an ipsilateral projection of glossopharyngeal fibers were found. These findings demonstrate that the glossopharyngeal nerve has more widely distributed brain stem projections that the vagus nerve and provide essential information on projection sites of visceral and taste inputs to the central nervous system.

Afferent Pathways↗
PubMed1987

Projections to areas of the nucleus tractus solitarii related to circulatory and respiratory responses in cats.

Using chloralose-anesthetized cats, afferent projections to the nucleus tractus solitarii (NTS) were studied in relation to circulatory and respiratory responses. Horseradish peroxidase (HRP) was injected into 3 distinct regions of the NTS: the rostral regions from which electrical stimulation elicited pressor and apneustic responses: the intermediate regions from which stimulation elicited depressor and apneic responses; the commissure regions from which stimulation elicited depressor and hypopneic responses. HRP-labeled cells were sought throughout the medulla oblongata upward including the telencephalon. The results indicate that: many neurons of the frontal cortex (sigmoid gyrus, anterior ectosylvian gyrus, anterior sylvian gyrus, and anterior suprasylvian gyrus) project bilaterally to the 3 regions, predominantly to the rostral regions; a few neurons of the bed nucleus of the stria terminalis project almost ipsilaterally to the 3 regions; a few neurons of the nucleus amygdalae centralis project almost ipsilaterally to the 3 regions; many neurons of the paraventricular nucleus project bilaterally to the 3 regions, predominantly to the ipsilateral commissure regions; a moderate number of neurons of the fastigial nucleus project contralaterally to the rostral regions. These findings suggest that there are some specific projections to each region of the NTS from various supramedullary nuclei, which may be involved in modulation of the cardiovascular and respiratory systems.

Animals↗
PubMed1981

Metabolic mapping of functional activity in the olfactory projections of the rat: ontogenetic study.

An ontogenetic study of the uptake of [14C]2-deoxy-D-glucose (2-DG) within the direct olfactory bulb projections and the tertiary olfactory projections was performed on rats of 1, 9 and 21 days old. Animals were exposed either to ethyl acetoacetate or to nest odor. In newborns, most of the direct olfactory bulb projections - anterior olfactory nucleus, anterior part of the olfactory tubercle, piriform cortex and nucleus of the lateral olfactory tract - appear labelled on films and therefore seem functional. No evidence of 2-DG uptake can be brought out in the cortical amygdala nucleus. AS regards the tertiary olfactory projections, there is no apparent functional activity, neither in the medio-dorsal and medio-ventral thalamic nuclei nor in the hypothalamic nuclei, e.g. the lateral preoptic area and the lateral hypothalamus. In 9-day-old pups, the direct olfactory bulb projections and the tertiary olfactory projections appear well-contrasted. Moreover, the patterns of labelling within the direct olfactory bulb projections are comparable to those observed in 21-day-old rats and in adult. These data are correlated with the postnatal development of the discriminating ability of the rat.

Aging↗
PubMed1984

The transience of cerebrocerebellar projections is due to selective elimination of axon collaterals and not neuronal death.

Fluorescent dyes were used to determine firstly if the transience of cerebrocerebellar projections in neonatal kittens is due to the selective elimination of axon collaterals or to neuronal death; and secondly, if the cerebrocerebellar projection neurons lived, did any maintain a projection to the brainstem or spinal cord. Injections of Fast Blue were made into the cerebellar cortex and deep nuclei in 7-9 postnatal days old kittens, the age in which cortical axons grow into the cerebellum. Later, at 31-71 postnatal days of age, when the transient cerebrocerebellar projections have disappeared, injections of Nuclear Yellow were made into the brainstem or the spinal cord. In the frontoparietal cortex, numerous neurons were labeled with Fast Blue suggesting that the disappearance of cerebrocerebellar projections is due primarily to the selective elimination of axon collaterals and not neuronal death. Moreover, many of the cortical neurons labeled with Fast Blue also were labeled with Nuclear Yellow which shows that many of the cortical neurons with transient collateral projections to the cerebellum in the neonate maintain a projection to brainstem or spinal targets in older animals.

Animals↗
PubMed1987

Development and plasticity in hamster trigeminal primary afferent projections.

At birth (gestational day 16), the hamster infraorbital nerve projects to the appropriate portion of the brainstem, though the projection lacks adult-like internal organization (patchiness). Infraorbital nerve damage at this time does not produce appreciable transganglionic atrophy in the central projections of the infraorbital nerve, but it does result in a failure to develop normal infraorbital primary afferent patches. Such damage also produces a more widespread central projection of spared mandibular afferents into regions occupied by 'regenerate' infraorbital terminals (J. Comp. Neurol., 235 (1985) 129-143). In the present study, transganglionic transport techniques were again used to show that, by postnatal day 5 (gestational day 21), rostrocaudally continuous aggregates of horseradish peroxidase-labelled infraorbital terminals are visible throughout the trigeminal brainstem nuclear complex. This aggregation pattern is nearly adult-like and isomorphic with the distribution of the mystacial vibrissae on the face. A similar infraorbital lesion performed on postnatal day 5, however, markedly decreased the density of the adult central projection of the infraorbital nerve to subnuclei principalis, oralis, interpolaris, and the magnocellular laminae of caudalis. The projection to superficial laminae of caudalis and the cervical dorsal horn was maintained. A postnatal-day-5 infraorbital lesion also failed to produce a more widespread central projection from spared mandibular primary afferents. These data suggest a relationship between the postnatal maturity of trigeminal primary afferents and the response of damaged and undamaged trigeminal afferents to infraorbital nerve transection in hamster. The similarity in the central primary afferent response to lesions at equivalent gestational times (postnatal days 5 and 0, respectively) in hamster and rat, suggests that this plasticity gradient may be a general characteristic of mammalian trigeminal primary afferents.

Afferent Pathways↗
PubMed1989

Pattern formation in the striatum: developmental changes in the distribution of striatonigral projections.

The mammalian striatum (the major subcortical structure in the telencephalon) can be divided into two compartments, the patch and the matrix, on the basis of various neurochemical and hodological markers expressed in the adult. The primary efferent target of striatal neurons is the substantia nigra. We have previously shown that the patch compartment sends projections to the substantia nigra embryonically; whereas the matrix does not form a similar projection until the early postnatal period (Fishell and van der Kooy, J. Neurosci., 7 (1987) 1969-1978). The projection of patch neurons to the substantia nigra is the earliest developmental marker for the patch compartment. Here we ask about the early distribution of patch projections and their possible relation to striatal compartmentalization. Embryonic anterograde axonal tracing of the striatonigral pathway can take advantage of the temporal separation of patch versus matrix projections to reveal the terminal distribution of patch striatonigral neurons independent of the nigral terminal distribution from the striatal matrix. The anterograde tracer rhodamine isothiocyanate was shown in a model system to persist in labeled neurons for more than a week, but to be available for uptake into these neurons for a few days after injection at the most. These properties of rhodamine isothiocyanate were combined experimentally with short and long term survival periods. This allowed assessment of the changing developmental distribution of nigral fibers from specifically the striatal patch compartment. In all experimental cases the anterogradely labeled sections of the substantia nigra were also stained with antibodies to tyrosine hydroxylase, which permitted differentiation of the dopamine cell rich pars compacta from the dopamine cell poor pars reticulata. The results show that in the adult the majority of patch and matrix striatonigral projections are confined to the substantia nigra pars reticulata. Furthermore, their fiber distribution within the pars reticulata is overlapping rather than complementary. Most interestingly, in the late embryonic period (most noticeably at embryonic day 19) there is a marked overlap between patch striatonigral fibers and nigral dopamine perikarya. By early postnatal times, when the matrix compartment begins to form its striatonigral projection, the overlap of patch striatonigral fibers and dopamine cells has largely disappeared. The results suggest that a transient interaction between patch striatonigral fibers and dopamine neurons (which is concomitant with the formation of striatal compartments), may be an important developmental event in the phenotypic maturation of striatal pa

Animals↗
PubMed1991

Evidence that the relative densities of afferents from both eyes control laminar distribution and binocular segregation of retinotectal projections in rats.

In the superior colliculus of normal rodents the crossed retinal projection overlaps the uncrossed projection. The present study describes an abnormal laminar distribution and binocular segregation of the retinotectal afferents induced after the experimental enlargement of the uncrossed retinotectal pathway in pigmented rats. Intraocular injections of anterograde tracers were used to investigate the topographic and laminar organization of retinotectal projections in adult rats given unilateral optic tract lesions at birth. These lesions are known to increase the number of ipsilaterally projecting ganglion cells in the opposite retina. The uncrossed retinal projection to the remaining superior colliculus forms an abnormal band of terminal labeling at the superficial half of the stratum griseum superficiale, markedly different from the laminar distribution of this pathway in unoperated controls. This abnormal uncrossed projection has its maximum density at the rostrolateral quadrant of the tectum. Within this region, the crossed retinotectal projection retracts from the surface of the superior colliculus, leading to partial binocular segregation. The results suggest that both the laminar distribution and the experimental binocular segregation of retinotectal afferents depend on the balance of the densities of the converging pathways from both eyes in the superior colliculus.

Animals↗
PubMed1994

Chronic embryonic MK-801 exposure disrupts the somatotopic organization of cutaneous nerve projections in the chick spinal cord.

The effect of altering neural activity on the development of the central projections of cutaneous and muscle sensory neurons was studied in the embryonic chick spinal cord. Animals were treated chronically with MK-801, a non-competitive N-methyl-D-aspartate receptor antagonist, during the period when both cutaneous and muscle sensory afferents form connections in the spinal cord. Daily applications of MK-801 began on embryonic day 5, 1 day before sensory collaterals penetrate the spinal cord gray matter, and continued until the animals were analyzed (at embryonic day 14). The patterns of cutaneous and muscle sensory nerve projections were determined by applying fluorescent tracers to individual, identified peripheral nerves. MK-801 treatment did not overtly alter the pattern of muscle afferent projections. However, in the MK-801-treated embryos, the somatotopic organization of cutaneous afferent projections was dramatically altered. Normally, the projections formed by the lateral femoral cutaneous and the medial femoral cutaneous nerves are located immediately adjacent to one another in the lumbar dorsal horn, with little overlap. In the MK-801-treated embryos, the projections from these two cutaneous nerves both expanded significantly within dorsal horn laminae to become almost completely superimposed. These data suggest that MK-801 disrupts the development of the somatotopic organization of cutaneous afferent projections in the spinal cord.

Afferent Pathways↗
PubMed1988

Zonal organization of olivo-nodulus projections in albino rabbits.

The organization of inferior olivary projections to the cerebellar nodulus in albino rabbits was assessed by autoradiographic, anterograde degeneration and retrograde transport techniques. These data indicate that the caudal aspect of the dorsal cap of Kooy projects to a band extending 0.5-1 mm lateral to the midline of the nodulus. The medial half of this region receives a projection from beta nucleus over at least the dorsal surface of the nodulus; an extension onto the ventral surface, though, is consistent with the anterograde tracing data. The rostral aspect of the dorsal cap and ventrolateral outgrowth projects to an adjacent 0.5-1 mm wide band in the nodulus. A group of cells spanning the intermediocaudal dorsal cap and the adjacent, dorsomedial margin of the beta nucleus appears to project laterally on the ventral surface of the nodulus. On the dorsal aspect of the nodulus and ventral surface of lobule IXd, though, comparisons of anterograde and retrograde tracing data suggest that this lateral field is innervated by the rostral aspect of the dorsomedial cell column and the rostromedial accessory olive. Finally, the regions of lobules X and IXd lining the posterolateral fissure represent a transition between lobule IX and ventral lobule X patterns of olivary projections. These data provide a basis for investigating the efferent projections of the nodulus to distinct olivo-vestibular terminal fields in the vestibular nuclei.

Animals↗
PubMed1979

Direct septo-hypothalamic projections in the rat.

Axonal projections from neurons located in the medial and lateral septal nuclei (MSN and LSN) were traced autoradiographically. The MSN projected bilaterally via a midline route to the diagonal band of Broca (DBB), the preoptic area (POA), the suprachiasmatic (SCN), paraventricular (PVN), ventromedial (VHM) and arcuate (ARC) nuclei including the median eminence (fiberous zone). Lateral coursing fibers traveled with the medial forebrain bundle (MFB) to the supraoptic (SON) and pre- and supra-mammillary nuclei. The majority of LSN axons projected to, and terminated in, the MSN. Fibers projected ipsilaterally through the POA, SON, SCN, ARC, ME and MMN with axonal projections observed throughout the MFB. In summary, the neurons of the MSN project to the medial hypothalamic nuclei via a midline route while LSN axons projected strongly to the MSN with the remaining fibers coursing along the ipsilateral MFB to terminate in several hypothalamic nuclei. These data indicate that a direct septo-hypothalamic pathway exists in the rat.

Animals↗
PubMed1986

The cerebellorubral projection in the rat: retrograde anatomical study.

The cerebellorubral projections have been studied in the rat using the retrograde transport of horseradish peroxidase-wheat germ agglutinin conjugate. The lateral cerebellar nucleus projects to the parvocellular red nucleus (RN), the anterior (NIA) and posterior (NIP) interposed nuclei project to the magnocellular RN. Whereas the projections from the NIP are limited to the medial aspect of the RN, those from the NIA extend throughout the magnocellular RN. NIA-RN projections are topographically arranged: the medial NIA projects ventrally, the lateral NIA projects dorsally. Functionally, this differential distribution seems to fit the hindlimb-forelimb areas of origin of the rubrospinal tract.

Animals↗
PubMed1987

The development of the corticotectal pathway in the albino rat: transient projections from the visual and motor cortices.

In rats ranging in age from the second postnatal day (23rd postconceptional day-23 PCD) to adulthood, we have studied the distribution of corticotectal terminals labelled anterogradely by unilateral injections of horseradish peroxidase (conjugated with wheat germ agglutinin) into the visual or motor cortices. No projection to the contralateral superior colliculus (SC) was observed. The earliest age at which the labelled axons and/or terminals from the visual cortex were observed in the ipsilateral SC was 25 PCD. At this stage the projection only involves the optic layer. From 28 to 34 PCD, the projection involves the optic layer, the intermediate layers and the deep part of superficial gray layer. Between 34 and 40 PCD the projection becomes restricted to the superficial laminae (i.e. adultlike). On the 23 PCD (the earliest age examined) we observed a projection from the motor cortex to the intermediate laminae and to a lesser extent the optic layer of the ipsilateral SC. By 34 PCD only the adult-like projection extending from the brachium to the periaqueductal gray (PAG) is apparent. The disappearance of the transient projections to the intermediate collicular laminae may be the result of withdrawal of 'misprojecting' axonal collaterals.

Animals↗
PubMed1988

Subtypes of neurones in Forel's field H as defined by their axonal projection.

Projection of neurones in Forel's field H (FFH) to the mesencephalon, the lower brainstem, and the upper cervical spinal cord (C1) was investigated by threshold mapping for evoking antidromic spikes from these areas. Projections of all FFH neurones tested were ipsilateral. Two main types (Type I and II) and their subtypes were differentiated from the pattern of the trajectories. Type Ia FFH neurones were found to project primarily to the oculomotor nucleus (IIIn) and the periaqueductal gray (PAG) bud did not descend down to the medulla, while Type Ib neurones projected to IIIn, PAG and the nucleus reticularis gigantocellularis (NRG) and Type Ic projected further down to the C1. Type II neurones were characterized by the absence of collaterals to IIIn. Type IIb projected to the cuneiform, subcuneiform and red nuclei in the mesencephalon and to the NRG, while Type IIc projected further down to the spinal cord. Type IIa neurones which terminated rostral to the NRG were found only rarely. These results suggested that Type Ib and Ic neurones are involved in the control of synergic eye and head movements, while Type IIb, IIc and Ia neurones are specified for the independent control of head and eye movement.

Action Potentials↗
PubMed1982

Effects of neonatal cortical lesions upon retinocollicular projections in the hamster.

Autoradiography and anterograde horseradish peroxidase transport were used to examine retinocollicular projections in normal hamsters and in animals subjected to ablation of the ipsilateral, posterior neocortex at 1, 3, 6, 10, or 120 days of age. The crossed retinotectal projections of all groups were quite similar. There did, however, appear to be a slight increase in the density of the projection to the lower portion of the stratum griseum superficiale in the neonatally brain-damaged hamsters. The uncrossed pathway, on the other hand, was quite abnormal in the neonatally lesioned animals. In normals, the ipsilateral retinocollicular projection consisted almost entirely of a series of patches along the stratum griseum superficiale-stratum opticum border in the rostral one-third of the colliculus. Only a few axons from the ipsilateral eye were observed in the caudal two-thirds of the tectum and these could only be visualized when horseradish peroxidase was used as the tracer. In all of the neonatally brain-damaged hamsters both autoradiography and horseradish peroxidase tracing demonstrated that the ipsilateral retina densely innervated the entire rostrocaudal extent of the colliculus. Retrograde tracing experiments demonstrated that the portion of the temporal retina which gave rise to the uncrossed retinocollicular projection in the normal hamsters was also the source of the expanded projection in the neonatally brain-damaged animals; and, further, that the numbers and areal distributions of ipsilaterally projecting retinal and retinocollicular ganglion cells were similar in the two groups. These findings suggest that, at least in the hamster, normal inputs from the two eyes may not be a sufficient condition for the development of the largely complementary pattern of collicular innervation by the two retinae.

Animals↗
PubMed1983

Do retinal and spinal projections overlap within the turtle thalamus?

The spinal and retinal projections to the turtle thalamus were studied using the autoradiographic tracing technique. Particular attention is given to the regions receiving both spinal and retinal projections: the ovalis complex and a perirotundal stripe. Spinal and retinal projections do not overlap significantly in either of these regions. In the perirotundal stripe there appears to be little likelihood of convergence of these projections on single neurons. In the ovalis complex, the most densely and the most consistently innervated thalamic region, however, the respective spinal and retinal target areas are located immediately adjacent to each other and low order somatosensory and visual projections may converge on single neurons with dendrites extending into both the spinal and retinal terminal arborizations. The ovalis complex in the turtle may be compared with the ventral part of the mammalian lateral geniculate nucleus. Both these nuclei receive spinal and retinal projections and both, reportedly, do not project to the telencephalon. The findings are discussed in relation to the possible evolution of the specific thalamic sensory nuclei in higher mammals as well as to the prosencephalic processing of somatosensory and visual information in turtles and mammals.

Animals↗
PubMed1983

The auditory brainstem nuclei and some of their projections to the inferior colliculus in the North American opossum.

Afferent projections to the inferior colliculus in the North American opossum have been examined using the retrograde transport of horseradish peroxidase. Projections to primarily the contralateral inferior colliculus arise in the dorsal and ventral cochlear nuclei, the auditory nerve nucleus and the spinal trigeminal nucleus pars caudalis, while ipsilateral projections arise in the superior paraolivary nucleus, the ventral nucleus of the trapezoid body, the ventral nucleus of the lateral lemniscus, the paralemniscal nucleus, the deep layer of the superior colliculus and the parabrachial nucleus. Bilateral projections to the inferior colliculus originate within the dorsal column nuclei, the nucleus reticularis gigantocellularis pars ventralis, the lateral and medial superior olivary nuclei, the dorsal nucleus of the lateral lemniscus and the auditory cortex. Nissl, fiber and Golgi-stained preparations were used to study the neuronal organization of those auditory nuclei with projections to the inferior colliculus. Anterograde axonal degeneration and transport techniques revealed that the inferior colliculus is innervated differentially by the dorsal and ventral cochlear nucleus, the superior olivary complex and the auditory neocortex. Axons from the contralateral dorsal cochlear nucleus and the ipsilateral superior olivary complex innervate both the central nucleus and external cortex, whereas those from ventral cochlear nucleus and contralateral, superior olivary complex project to only the central nucleus. Projections from auditory cortex form the complement of those from the cochlear nuclei and superior olivary complex, that is, they terminate in a thin band overlying the dorsal cortex and the superficial layer of external cortex. Our results have been compared with those obtained from eutherian mammals and it is clear that there are striking similarities in neuronal organization and connectivity. Since the opossum is born 12 days after conception and has an extended development in an external pouch, it may be suited for developmental studies of the mammalian auditory connections and the behaviors dependent of them.

Aging↗
PubMed1983

Projections from brain stem nuclei to the spinal trigeminal nucleus in the cat.

Afferent projections to the trigeminal nucleus oralis and caudalis from the brain stem have been investigated by the use of retrograde transport of horseradish peroxidase in the cat. Both n. oralis and n. caudalis receive a projection from nucleus raphe magnus but not from other raphe nuclei in the medulla or pons. N. oralis and n. caudalis receive a bilateral projection from n. paragigantocellularis lateralis. N. oralis receives a projection from n. reticularis gigantocellularis and n. reticularis parvocellularis but not from n. reticularis magnocellularis. N. caudalis receives only sparse projections from n. reticularis gigantocellularis, n. reticularis parvocellularis and n. reticularis magnocellularis but receives an input from a layer of cells over the pyramids in the rostral medulla, here named n. paramagnocellularis ventralis. The study also revealed the presence of ascending and descending interconnections between n. oralis and n. caudalis, as well as contralateral trigeminal interconnections. Projections from the medial vestibular nuclei, n. praepositus hypoglossi and the facial nucleus to the spinal trigeminal nucleus were also noted. Since the spinal trigeminal nucleus has only sensory functions, the results indicate the source of projections, mainly from raphe and reticular nuclei, which are involved in sensory control in the trigeminal system.

Afferent Pathways↗
PubMed1985

The cytoarchitecture, histochemistry and projections of the tuberomammillary nucleus in the rat.

The normal morphology, efferent projections and possible neurotransmitter content of neurons in the tuberomammillary nucleus (caudal magnocellular nuclei of Bleier et al.) [Bleier, Cohn and Siggelkow (1979) In Anatomy of the Hypothalamus, Vol. 1, pp. 137-220] have been examined in the adult male rat. In Nissl-stained sections, the nucleus can be divided into a dorsomedial, ventral and diffuse part, each of which consists of large, darkly stained neurons cradling the mammillary body. The ventral part is by far the largest and consists of some 2500 neurons on each side of the brain. Immunohistochemical studies indicate that a majority of the large neurons in all three parts of the nucleus stain with antisera against glutamate decarboxylase and [Met]enkephalyl-Arg6-Phe7 heptapeptide and that a smaller subset of these neurons (about 10%) also stain with an antiserum against substance P. Single injections of retrogradely transported fluorescent tracers were made into 18 different sites in 86 animals and the results indicate that all three parts of the tuberomammillary nucleus on one side of the brain send fibers to or through various parts of the neocortex, hippocampal formation, amygdala, basal ganglia, thalamus, superior colliculus and cerebellum on both sides of the brain and that the projection neurons are not organized in a highly topographic way. Injections of two different fluorescent tracers in the same animal indicate that individual neurons in the nucleus may give rise to both ascending and descending projections, as well as projections to widely divergent parts of the forebrain. Together with previous results, this evidence suggests that the tuberomammillary nucleus has widespread projections to the numerous brain structure located in the forebrain and in the caudal medulla (it may not project to the spinal cord), and that its axons may release a mixture of neuroactive substances including gamma-amino butyrate and several peptides. Although its functional significance remains to be investigated, morphological evidence suggests that the tuberomammillary nucleus may constitute one of a series of neurotransmitter-specific cell groups in the brainstem and basal forebrain with diffuse efferent projections that may be involved in the modulation of attention or behavioral state, rather than the processing of specific sensory or motor information.

Amidines↗