大鼠前庭神经核群向腰髓投射特征——BDA法逆行研究

目的　研究大鼠前庭神经核群向脊髓的投射纤维特征。方法　在 7例SD大鼠采用结合生物素的葡聚糖胺(BDA)逆行法观察大鼠前庭核群向脊髓的投射。结果　除前庭神经上核 (SVN)外的其余各前庭核均有向大鼠腰髓的投射 ,单侧注射的实验动物中 ,前庭神经内侧核 (MVN)、外侧核 (LVN)和降核 (DVN)的标记神经元可见于双侧 ,其中MVN和LVN的标记神经元以注射同侧占优势 ,而DVN标记神经元两侧数量基本一致。结论　大鼠前庭脊髓尾侧束发出纤维投向脊髓腰段     

Connections of Purkinje cell axons of lobule X with vestibulospinal neurons projecting to the cervical cord in the rat

Connections of Purkinje cell axons of lobule X (nodulus vermis) with vestibulospinal neurons have been demonstrated in the rat, by anterograde labeling of axons with biotinylated dextran (BD) injected into sublobule Xa and by retrograde labeling of neurons with cholera toxin subunit B (CTB) injected into cervical segments. Labeled terminals of Purkinje cell axons were numerous in the superior vestibular nucleus, the parvocellular (MVpc) and the caudal part (MVc) of the medial vestibular nucleus (MV), and group y. A limited number of labeled terminals were seen in the caudal part of the descending vestibular nucleus (DV). Occasional labeled terminals were seen in the lateral part of the lateral vestibular nucleus (LV) whereas few labeled terminals were seen in the magnocellular part of the MV (MVmc). Vestibulospinal neurons labeled from the C2 and C3 segments were seen bilaterally in the MVmc, MVpc, MVc, and DV, and ipsilaterally in the LV. CTB-labeled vestibulospinal neurons in contact with BD-labeled terminals of Purkinje cell axons were identified in the lateral part of the MVpc, near the border between the MVpc and MVmc, or close to the dorsal acoustic stria, and in the middle part of the MVc at its rostral level. The present study suggests that Purkinje cells of lobule X regulate the output of cervical-projecting vestibulospinal neurons in the MVpc and MVc.     

Properties of utricular-activated vestibular neurons that project to the contralateral vestibular nuclei in the cat

The properties of utricular (UT)-activated vestibular neurons that send axons to the contralateral vestibular nuclei (commissural neurons) were investigated intracellularly or extracellularly in decerebrate cats. A total of 27 vestibular neurons were orthodromically activated by stimulation of UT nerves and antidromically activated by stimulation of the contralateral vestibular nuclei. All neurons tested were classified as vestibulospinal (VS), vestibulooculospinal (VOS), vestibuloocular (VO), and unidentified vestibular neurons (V) after antidromic stimulation of the spinal cord and oculomotor/trochlear nuclei. Most UT-activated commissural neurons (20/27) received monosynaptic inputs. Twelve of 27 commissural neurons were located in the medial vestibular nucleus, 5 were in the lateral vestibular nucleus, 10 were in the descending vestibular nucleus, and no commissural neurons were recorded in the superior vestibular nucleus. Seven of 27 neurons were commissural VS neurons, 9 of 27 were commissural VOS neurons, and 11 of 27 were commissural V neurons. No commissural VO neurons were found. All VOS neurons and 3 VS neurons issued descending axons via the medial vestibulospinal tract. We also studied convergent inputs from the posterior semicircular canal (PC) nerve onto UT-activated commissural neurons. Five of 27 UT-activated commissural neurons received converging inputs from the PC nerves. Electronic Publication     

A direct projection from the medial vestibular nucleus to the cervical spinal dorsal horn of the rat, as demonstrated by anterograde and retrograde tracing

Summary Phaseolus vulgaris leucoagglutinin and wheat germ agglutinin-horseradish peroxidase were iontophoretically injected into different parts of the vestibular nuclear complex (VNC) of the rat. Injections centered into the caudal part of the medial vestibular nucleus revealed a vestibulospinal projection predominantly to the dorsal horn of the cervical spinal cord, besides the expected projection to the intermediate zone (IZ) and ventral horn (VH). While most of the anterogradely labelled fibres could be localized in laminae III to V, some scattered fibres were also seen in laminae I and VI. Lamina II remained free of labelling. The dorsal horn (DH) area with detectable anterograde labelling showed a rostrocaudal extension from C₁-C₆. Injections into other parts of the VNC labelled fibres and terminals in the IZ and VH while the DH remained almost free of labelling. Additionally, fluorogold and wheat germ agglutininhorseradish peroxidase were pressure- or iontophoretically injected at different levels into the spinal cord to confirm the projection to the dorsal horn by means of retrograde tracing. Labelled neurons in the area of the medial vestibular nucleus (MVN), from which anterograde labelling in the DH was obtained, were only detectable after fluorogold and wheat germ agglutinin-horseradish peroxidase injections into the cervical spinal cord, in particular its DH. This projection from the caudal medial vestibular nucleus to the dorsal horn of the cervical spinal cord probably enables the VNC to influence sensory processing in the DH, in addition to its well-established influence on posture and locomotion via projections to the intermediate zone and ventral horn.Abbreviations BSA bovine serum albumin - CuN cuneate nucleus - CCN central cervical nucleus - cMVN caudal medial vestibular nucleus - cVST caudal vestibulospinal tract - DAB diaminobenzidine - DH dorsal horn - DRG dorsal root ganglia - DVN descending vestibular nucleus - ECN external cuneate nucleus - FCS fetal calf serum - FG fluorogold - HRP horseradish peroxidase - icp inferior cerebellar peduncle - In intercalated nucleus - IZ intermediate zone - LVN lateral vestibular nucleus - LVST lateral vestibulospinal tract - mlf medial longitudinal fasciculus - MVN medial vestibular nucleus - MVST medial vestibulospinal tract - PHA-L Phaseolus vulgaris leucoagglutinin - PrH praepositus hypoglossi nucleus - rMVN rostral medial vestibular nucleus - Ro Roller's nucleus - SVN superior vestibular nucleus - TMB tetramethylbenzidine - VH ventral horn - VNC vestibular nuclear complex - WGAHRP wheat germ agglutinin-horseradish peroxidase - 12 hypoglossal nucleus Dedicated to Prof. J.W. Rohen on the occasion of his 70th birthday     

Ipsilateral and contralateral projections to the trochlear nucleus arise from different subdivisions in the vestibular nuclei

Vestibular neurons that project to the trochlear nucleus were studied following unilateral injections of horseradish peroxidase. After 48 h, the animals were perfused, transverse sections were cut, and reacted with diaminobenzidine. After injections centered on the trochlear nucleus, one-third of the labeled neurons were located in the ipsilateral superior (S) vestibular nucleus and almost half were in the contralateral medial (M) vestibular nucleus. Labeled fibers were restricted to the medial longitudinal fasciculus ipsilateral to the injection. This study supports hypotheses, based on physiological data of two vertical vestibulo-ocular pathways; one originating in the ipsilateral S that may be inhibitory and the second originating predominantly from the contralateral M that may be excitatory.     

Anterograde tracing of projections from the dorsal raphe nucleus to the vestibular nuclei

This study used the anterograde transport of biotinylated dextran amine (BDA) to identify the course and terminal distribution of projections from the dorsal raphe nucleus (DRN) to the vestibular nuclei in rats. After iontophoretic injection of BDA into the medial and lateral regions of DRN, anterogradely labeled fibers descend within the medial longitudinal fasciculus and the ventricular fiber plexus to terminate within two discrete regions of the vestibular nuclear complex. One terminal field was located primarily ipsilateral to the injection site and involved rostrodorsal aspects of the vestibular nuclei, including superior vestibular nucleus and rostral portions of the medial vestibular nucleus (MVN) and lateral vestibular nucleus (LVN). The other terminal field involved caudoventral aspects of both ipsilateral and contralateral MVN and LVN and was less heavily innervated. These findings confirm that the vestibular nuclei are targeted by a regionally-selective projection from the DRN. The segregation of DRN terminals into anatomically distinct fields indicates that the DRN-vestibular nucleus projections are organized to selectively modulate processing within specific functional domains of the vestibular nuclear complex. In particular, these terminal fields may be organized to modulate vestibular regions involved in eye movement-related velocity storage, coordination of vestibular and affective responses, and the bilateral coordination of horizontal eye movement reflexes.     

Excitatory connections between neurons of the central cervical nucleus and vestibular neurons in the cat

 The central cervical nucleus (CCN) of the cat receives input from upper cervical muscle afferents, particularly primary spindle afferents. Its axons cross in the spinal cord, and while in the contralateral restiform body give off collaterals to the vestibular nuclei. In order to study the connections between CCN axons and vestibular neurons, we stimulated the area of the CCN in decerebrate cats while recording intra- or extracellularly from neurons in the contralateral vestibular nuclei. CCN stimulation evoked excitatory postsynaptic potentials (EPSPs) or extracellularly recorded firing in the lateral, medial and descending vestibular nuclei. The latency of EPSPs (mean 1.6 ms) was on average 0.4 ms longer than the latency of antidromic spikes evoked in the CCN by stimulation of the contralateral vestibular nuclei (mean 1.2 ms), demonstrating that the excitation was typically monosynaptic. The results provide further evidence that the CCN is an important excitatory relay between upper cervical muscle afferents and neurons in the contralateral vestibular nuclei. Received: 1 August 1996 / Accepted: 16 December 1996     

Non-cerebellar visual afferents to the vestibular nuclei involving the prepositus hypoglossal complex: An autoradiographic study in the rat

Summary Radioactive amino-acids were injected into the nucleus reticularis tegmenti pontis (NRTP) and the pretectum (PT) in the rat. Beside the labeling of the several nuclei which are known to receive afferents of either the NRTP and/or the PT, monosynaptic projections from these two structures to the prepositus hypoglossal complex (PHN) were demonstrated. Pretectal visual inputs to the vestibular nuclei (VN) may thus be conveyed not only by the classical PT-inferior olive-cerebellar route, but also by two other non-cerebellar ones involving the strong efferent projections of the PHN onto the VN. These last two pathways are strong candidates to account for the residual visual sensitivity of VN neurons after cerebellectomy or inferior olive lesions.Supported by CNRS (A.T.P. 8115)     

A cervical primary afferent input to vestibular nuclei as demonstrated by retrograde transport of wheat germ agglutinin-horseradish peroxidase in the rat

Summary Wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) was microiontophoretically injected into the vestibular nuclear complex of the rat. Retrogradely labeled neurons were found in ipsilateral spinal ganglia C₂-C₃ only if the injection site was in the caudal part of the medial vestibular nucleus (MVN). Injections into rostral parts of the MVN, the superior, lateral and descending vestibular nuclei (SVN, LVN, DVN), the nucleus of the solitary tract (STN) and the reticular formation did not result in spinal ganglion labeling. Thus, the caudal part of the MVN appears to be the main vestibular termination site for rostral cervical primary afferents.Abbreviations Cu cuneate nucleus - DVN descending vestibular nucleus - ECN external cuneate nucleus - g7 genu of the facial nerve - icp inferior cerebellar peduncle - In intercalated nucleus - LVN lateral vestibular nucleus - mlf medial longitudinal fasciculus - MVN medial vestibular nucleus - PrH prepositus hypoglossi nucleus - Ro Roller's nucleus - sol solitary tract - SVN superior vestibular nucleus - 12 hypoglossal nucleus     

Vestibular nerve and nuclei unit responses and eye movement responses to repetitive galvanic stimulation of the labyrinth in the rat

Summary Two-second cathodal current pulses were applied at one-minute intervals at a point external to the round window in the ear of each albino rat subject. Responses were recorded in the vestibular nerve ganglion, the vestibular nuclei (single units), or in the eye movements (search coil recording method) of anaesthetized, decerebrated, or alert rats. The unit responses to the galvanic stimuli were characterized and compared with responses to galvanic and rotational stimuli reported in the literature. The main focus of the study, however, was effects of stimulus repetition. In both the vestibular nerve and vestibular nuclei recordings, the responses of many units were substantially larger or smaller at the end of a 13-pulse stimulus train than at the beginning. In the vestibular nuclei, but not in the nerve, there was a slight bias towards a decrease in response magnitude, with 10/88 units showing decreases great enough to be considered as reflecting an habituation process. In contrast, the eye movement responses showed more consistent response decrements, especially in the alert condition, but also in the other conditions (none of the unit recordings were done in alert rats). It is concluded that some of the modifications underlying habituation of the vestibuloocular reflex probably occur in portions of the neuronal reflex pathways that are downstream from the vestibular nuclei.Prof. Precht died on March 12, 1985     

Responses of neurons in the caudal medullary raphe nuclei of the cat to stimulation of the vestibular nerve

Summary In the decerebrate cat, recordings were made from neurons in the caudal medullary raphe nuclei to determine if they responded to electrical stimulation of the vestibular nerve and thus might participate in vestibulo-sympathetic reflexes. Many of these cells projected to the upper thoracic spinal cord. The majority (20/28) of raphespinal neurons with conduction velocities between 1 and 4 m/s received vestibular inputs; 13 of the 20 were inhibited, and 7 were excited. Since many raphespinal neurons with similar slow conduction velocities are involved in the control of sympathetic outflow, as well as in other functions, these cells could potentially relay vestibular signals to sympathetic preganglionic neurons. The onset latency of the vestibular effects was long (median of 15 ms), indicating the inputs were polysynaptic. In addition, 34 of 42 raphespinal neurons with more rapid conduction velocities (6–78 m/s) also received long-latency (median of 10 ms) labyrinthine inputs; 26 were excited and 8 were inhibited. Although little is known about these rapidlyconducting cells, they do not appear to be involved in autonomic control, suggesting that the function of vestibular inputs to raphe neurons is not limited to production of vestibulosympathetic reflexes. One hypothesis is that raphe neurons are also involved in modulating the gain of vestibulocollic and vestibulospinal reflexes; this possibility remains to be tested.     

Immunohistochemical demonstration of regionally selective projections from locus coeruleus to the vestibular nuclei in rats

Summary This study describes a regionally selective projection of tyrosine hydroxylase and dopamine -hydroxylase-immunoreactive fibers from locus coeruleus (LC) and the A4 region of nucleus subcoeruleus to the vestibular nuclear complex in Long-Evans and Sprague-Dawley rats. These fibers travel in two distinct pathways. A lateral descending noradrenergic bundle provides input from LC to the superior vestibular nucleus (SVN), the cochlear nuclei, and the cerebellar cortex. A medial descending noradrenergic bundle provides input to the lateral vestibular nucleus (LVN), medial vestibular nucleus (MVN), and the inferior vestibular nucleus (IVN) before continuing on to the cochlear and cerebellar nuclei. The terminal plexus of these fibers varies markedly across these vestibular nuclear regions. Immunoreactive axons form a dense plexus around somata and proximal dendrites of Deiters' neurons in dorsal LVN. The axon plexus is less dense in SVN and ventral LVN, and relatively sparse in MVN and IVN. This regional selectivity of noradrenergic innervation suggests that central adrenergic systems may selectively modulate vestibulospinal reflexes at the level of the vestibular nuclear complex.     

Descending projections from the subparafascicular thalamic nucleus to the lower brain stem in the rat

Summary In the course of our study on the neuronal connections of the subparafascicular nucleus (SPF) in the rat, descending projections from the SPF to the lower brain stem were examined by using the anterograde tracer PHA-L (Phaseolus vulgaris leukoagglutinin) and retrograde tracer WGA-HRP (horseradish peroxidase conjugated to wheat germ agglutinin). When PHA-L was injected into the magnocellular and/or parvicellular division of the SPF (SPFm and/or SPFp), presumed terminal labeling was seen, bilaterally with an ipsilateral dominance, in the mesencephalic and pontine central gray matter, peripheral shell regions of the inferior colliculus, cuneiform nucleus, and superior olivary complex (mainly in the superior paraolivary nucleus, and additionally in the nuclei of the trapezoid body). A few labeled axon terminals were also seen in the cochlear nuclei bilaterally with a contralateral dominance. In the second set of experiments, WGA-HRP was injected into the inferior colliculus, superior olivary complex, or cochlear nuclei. When WGA-HRP was injected into the peripheral shell regions of the inferior colliculus or the superior olivary complex, many labeled neuronal cell bodies were seen in the SPFm bilaterally with an ipsilateral dominance, and a moderate number of labeled neuronal cell bodies were observed in the SPFp (lateral SPF) bilaterally with an ipsilateral dominance. When WGA-HRP was injected into the cochlear nuclei, a moderate number of labeled neuronal cell bodies were observed in the SPFm and SPFp bilaterally with a contralateral dominance. The results indicate that the SPFm and SPFp (lateral SPF) of the rat send a considerable number of projection fibers to the lower brain stem. The target regions of these projection fibers include the auditory relay nuclei, such as the inferior colliculus, superior olivary complex, and cochlear nuclei.     

Serotonergic and nonserotonergic neurons in the dorsal raphe nucleus send collateralized projections to both the vestibular nuclei and the central amygdaloid nucleus

Using a combination of double retrograde tracing and serotonin immunofluorescence staining, we examined whether individual serotonergic and nonserotonergic neurons in the dorsal raphe nucleus are sources of collateralized axonal projections to vestibular nuclei and the central amygdaloid nucleus in the rat. Following unilateral injections of Diamidino Yellow into the vestibular nuclei and Fast Blue into the central amygdaloid nucleus, it was observed that approximately one-fourth of the dorsal raphe nucleus neurons projecting to the vestibular nuclei send axon collaterals to the central amygdaloid nucleus. Immunofluorescence staining for serotonin revealed that more than half of the dorsal raphe nucleus neurons from which these collateralized projections arise contain serotonin-like immunoreactivity. These findings indicate that a subpopulation of serotonergic and nonserotonergic dorsal raphe nucleus cells may act to co-modulate processing in the vestibular nuclei and the central amygdaloid nucleus, regions implicated in the generation of emotional and affective responses to real and perceived motion.     

Cytosolic glucocorticoid receptor expression in the rat vestibular nucleus and hippocampus following unilateral vestibular deafferentation

It has been suggested that vestibular compensation, the process of behavioural recovery that occurs following peripheral vestibular damage, might be partially dependent on the release of glucocorticoids (GC) during the early stages of recovery from the lesion. One possibility is that glucocorticoid receptors (GRs) in the vestibular nucleus complex (VNC) might change following the lesion, altering their response to GCs. We sought to test this hypothesis by quantifying the expression of cytosolic GRs in the bilateral VNCs at 10 h, 58 h and 2 weeks following unilateral vestibular deafferentation (UVD) in rat, using western blotting. We also examined GR expression in the CA1, CA2/3 and dentate gyrus (DG) subregions of the hippocampus and measured serum corticosterone levels. Compared with sham surgery and anaesthetic controls, we found no significant changes in GR expression in the ipsilateral or contralateral VNCs at any time post-UVD. However, we did find a significant decrease in GR expression in the ipsilateral CA1 at 2 weeks post-UVD. Serum corticosterone levels were significantly lower in all groups at 58 h post-op. compared to 10 h and 2 weeks; however, there were no significant differences between the UVD and control groups at any time point. These results suggest that changes in GR expression in the VNC are unlikely to contribute to the development of vestibular compensation. However, long-term changes in GR expression in CA1 might be related to chronic deficits in hippocampal function and spatial cognition following vestibular damage.     

The location of brainstem neurons with bilateral projections to the motor nuclei of jaw openers in the cat

Symmetrical motor output is the rule in the masticatory system. We examined morphologically how this functional symmetry might be reflected in the organization of premotor neurons that could mediate excitation of jaw-opener motoneurons. Premotor neurons projecting bilaterally to jaw-opener motoneurons by way of axon collaterals were identified by retrograde dual-labeling with cholera toxin B-conjugated fluorescein isothiocyanate (CTb-FITC) and tetramethylrhodamine (TMR). In each cat, CTb-FITC and TMR were injected into the digastric motoneuron pools, respectively, on the left and right sides. In three animals, 69-147 neurons were labeled with both tracers, comprising approximately 44% of all retrogradely labeled cells. Double-labeled cells were located bilaterally in the trigeminal oral nucleus (Vo) and the adjacent reticular formation (RF), the former containing a larger number of cells. Neurons labeled with only one tracer were also distributed bilaterally in the Vo and RF. The results indicated that the bilaterally projecting premoter neurons identified mainly in the Vo and RF represent neuronal substrates for the symmetry that characterizes most jaw movements.     

Topographic relationship between sagittal Purkinje cell bands revealed by a monoclonal antibody to zebrin I and spinocerebellar projections arising from the central cervical nucleus in the rat

Summary We have examined the topographic relationship between the sagittal bands of zebrin I immunoreactive Purkinje cells revealed by a monoclonal antibody, mabQ113, and the distribution of spinocerebellar fibers originating from the central cervical nucleus in the rat. The mossy fiber terminals were anterogradely labeled following injections of cholera toxin subunit B into the C1–C3 segments and visualized immunohistochemically. Zebrin I positive Purkinje cells appeared in seven sagittal bands (P1+ to P7+ bands). In lobules I–V of the anterior lobe, labeled mossy fiber terminals were distributed in the midline region, subjacent to the P1+ bands and at around 0.5 mm from the midline region, subjacent to the P2+ band in the lateral A1 to the medial A2 zones of Voogd et al. (1985). Labeled terminals were seen in the entire B zone and those distributed in its medial part were related to the P3+ band. In lobule VIII, labeled terminals were seen subjacent to the P1+, P2+ and P3+ bands, which were located in the lateral A1–A3 (or B) zones. In the copula pyramidis, labeled terminals appeared subjacent to the P4+, P5+ and the P6+ bands in the C1 and C2 zones (or the C1-C3 zones). Although the labeled terminals were seen beneath the zebrin I positive bands, the borders of terminal distribution were not well-delineated, and did not respect the borders of zebrin I positive bands.On leave from the Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Ibaraki 305, Japan     

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

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

The vestibular nuclei of the cat receive a primary afferent projection from receptors in extraocular muscles

Summary The vestibular nuclei of adult cat were injected with retrogradely transported tracers, WGA-HRP or fluorescent Diamidino-Yellow. Labelled cells were found in the caudal half of the ipsilateral mesencephalic trigeminal nucleus, in the area where ganglionic cells of the sensory receptors in the extraocular muscles have previously been described. Double labelling experiments were carried out with Diamidino Yellow injected in vestibular nuclei and Fast Blue in extraocular muscles. Some cells in the mesencephalic trigeminal nucleus were found to contain both tracers, providing evidence that vestibular neurons do receive direct afferent signals from extraocular muscles. Therefore, this anatomical demonstration suggests a direct feed-back control between the extraocular muscle receptors and the vestibular nuclei.     

Neuropeptide FF in the lateral spinal and lateral cervical nuclei: Evidence of contacts on spinothalamic neurons

Neuropeptide FF (NPFF, F8Famide) is best known for its modulating effect on opioid analgesia and morphine tolerance. However, the exact mode of action of NPFF in sensory transmission is not known. We compared the distribution of NPFF-immunoreactive (ir) fibers and terminal-like thickenings with the retrograde, tracer-filled spinothalamic (ST) neurons in the lateral spinal nucleus (LSN) and lateral cervical nucleus (LCN) of rat, areas where NPFF-containing nerve terminals are abundant. We injected fluorescent latex microspheres into the ventroposterolateral thalamic nucleus and more medial thalamic nuclei, which are innervated by ST neurons. We found NPFF-ir terminal-like thickenings and fibers apposing the tracer-filled neurons in the LSN and LCN. ST neurons filled with the retrograde tracer making contacts with NPFF-ir terminal-like thickenings, were found to terminate not only in the ventroposterolateral thalamic nucleus but also in more medial thalamic nuclei. The highest number of tracer-filled ST neurons having NPFF-ir terminal-like thickenings and fibers in apposition were found at the cervical level. Our results suggest that NPFF-containing systems in the spinal cord of rat are not limited to the substantia gelatinosa, and the sensory functions of NPFF may be mediated at least partly through the modulation of the ST system. NPFF-ir contacts in the LSN and LCN might play an important role in the somatic sensory transmission system. This study shows evidence for the first time that the spinal NPFF-containing system may be involved in mechanisms that control sensory input to the supraspinal levels. Received: 11 March 1997 / Accepted: 10 September 1997