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At least 145 records · Page 8Linked to original sources

PubMed1993

Direct projection from the nucleus of the optic tract to the medial vestibular nucleus in the cat.

The nucleus of the optic tract (NOT) serves as an important visuo-motor relay between the retina and preoculomotor structures that mediate optokinetic nystagmus. In the present study, the efferent targets of NOT were investigated using biocytin as an anterograde tracer. Following biocytin injections into NOT, labeled fibers were observed in each of the following efferent pathways: (1) those that project to the contralateral NOT via the posterior commissure; (2) those that course through the nucleus reticularis pontis oralis to terminate in the nucleus reticularis tegmenti pontis; and (3) those that descend via the medial lemniscus to the level of the medulla to terminate in the dorsolateral pontine nucleus, nucleus prepositus hypoglossi, medial vestibular nucleus and the inferior olive. Direct projections from the NOT to the medial vestibular nucleus may contribute to the residual optokinetic responses of the vestibular nucleus neurons following cerebellar or inferior olivary lesions.

Animals↗

PubMed1983

Branched output neurons of the rat subthalamic nucleus: electrophysiological study of the synaptic effects on identified cells in the two main target nuclei, the entopeduncular nucleus and the substantia nigra.

The synaptic responses of entopeduncular and nigral cells to subthalamic stimulation were studied with extracellular recording techniques in rats with and without chronic lesions. Entopeduncular output cells were identified by antidromic activation from the lateral habenula, ventral anterior thalamic nucleus and tegmenti pedunculopontine nucleus. Nigral cells projecting to superior colliculus were identified by antidromic discharge. Stimulation of the subthalamic nucleus produced a short latency suppression of spontaneous activity (10-60 ms duration) of 89% of the entopeduncular cells tested in chronically lesioned rats. Of these cells, 50% were identified as projecting to lateral habenula. On the other hand, subthalamic nucleus stimulation produced a short latency excitation of 73% of the nigral cells tested (4.16 +/- 0.07 ms). Forty-eight percent of these cells projected to superior colliculus. The subthalamic fibres which terminate in entopeduncular nucleus and substantia nigra, come from the same neuronal population since the majority, if not all, rat subthalamic neurones send branched projections to both these nuclei. Therefore, the two different types of responses recorded in these nuclei are elicited by the activation of a single neuronal population. This dual effect could be easily explained if one of the responses is mediated by local interneurones. If not, the same transmitter induces the two responses. The entopeduncular nucleus and substantia nigra which are the main target nuclei of the subthalamic nucleus, are also the only known outputs of the striatum. The subthalamic efferent cells could thus modulate the activity of the entire striatal descending output. It is noteworthy that this subthalamic control is different in entopeduncular nucleus than in substantia nigra.

Animals↗

PubMed2006

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.

Amidines↗

PubMed2000

Synaptic contacts between serotonergic and cholinergic neurons in the rat dorsal raphe nucleus and laterodorsal tegmental nucleus.

We examined synaptic connectivity between cholinergic and serotonergic neurons in the dorsal raphe nucleus and the laterodorsal tegmental nucleus of the rat. To this purpose we employed two variations (the combination of pre-embedding immunogold-silver intensification with avidin-biotin-peroxidase complex technique and the combination of avidin-biotin-peroxidase/3, 3'-diaminobenzidine/silver-gold intensification with avidin-biotin-peroxidase/3,3'-diaminobenzidine reaction) of a double pre-embedding immunoelectron procedure, using primary antibodies against vesicular acetylcholine transporter and serotonin. At the light-microscopic level, serotonin-like immunoreactive neurons in the dorsal raphe nucleus appeared as reddish black and vesicular acetylcholine transporter-like immunoreactive axon terminals were brown colored using a combination of pre-embedding immunogold-silver technique and avidin-biotin-peroxidase complex technique. Serotonin-like immunoreactive fibers projected to the laterodorsal tegmental nucleus. At the electron microscopy level, with both methods we observed in the dorsal raphe nucleus vesicular acetylcholine transporter-immunopositive axon terminals in synaptic contact with serotonin-like immunoreactive dendrites and, to a lesser degree, with serotonin-like immunoreactive cell bodies. These synapses usually were of the symmetrical type. Occasionally we noted, next to vesicular acetylcholine transporter-immunopositive axon terminals, also immunonegative terminals synapsing with the serotonin-like immunoreactive dendrites. In the laterodorsal tegmental nucleus we found serotonin-like immunoreactive axon terminals and immunonegative terminals forming synapses with vesicular acetylcholine transporter-immunoreactive dendrites. Most synapses formed by the serotonin-like immunopositive terminals were of the asymmetrical type. Our results suggest that serotonergic neurons in the dorsal raphe nucleus and cholinergic neurons in the laterodorsal tegmental nucleus may reciprocally influence each other by means of synaptic connectivity. Such connectivity may serve to regulate pain sensation, or be involved in the regulation of the sleeping-waking cycle.

Acetylcholine↗

PubMed1985

Noradrenergic alpha 2 binding sites in vagal dorsal motor nucleus and nucleus tractus solitarius: autoradiographic localization.

The distribution in the canine medulla oblongata of binding sites for p-[3H]aminoclonidine, a ligand specific for alpha 2-adrenergic receptors, was studied with light microscopic autoradiographic methods. Specific labelling was determined using unlabelled phentolamine as a displacer. The greatest density of sites was localized in the dorsal motor nucleus of the vagus nerve, the area postrema, and in several regions of the nucleus tractus solitarius. Less dense binding of the radioligand was also seen in the inferior olivary nucleus. Dorsomedial regions of the nucleus tractus solitarius were the most densely labelled in this nucleus, and dorsolateral and ventral regions were much less densely labelled. The region of the nucleus tractus solitarius shown in this study to be heavily labelled with alpha 2-adrenergic binding sites has been implicated in the autonomic control of blood pressure. The dorsal motor nucleus of the vagus, together with the nucleus tractus solitarius, may thus represent the site of the antihypertensive action of the drug clonidine, an alpha 2-adrenoreceptor agonist.

Animals↗

PubMed2004

Reciprocal neural connections between the central posterior/prepacemaker nucleus and nucleus G in the gymnotiform fish, Apteronotus leptorhynchus.

The central posterior nucleus of teleost fish is a cluster of neurons in the dorsal thalamus that plays an important role in controlling social behaviors. In the weakly electric gymnotiform fish, Apteronotus leptorhynchus, this nucleus forms a larger complex together with the prepacemaker nucleus, hence called central posterior/prepacemaker nucleus (CP/PPn). This complex is crucially involved in neural control of transient modulations of the electric organ discharge, which occur both spontaneously and in the context of social interactions. This control function is intimately linked to its pattern of connectivity with other brain regions. By employing an in vitro neuronal tract-tracing technique, we have, in the present study, identified a novel reciprocal connection between the CP/PPn and a cell group situated in the region between the ventral thalamus and the inferior lobe. Despite the previous interpretation by other authors of this cell group as the glomerular nucleus, the lack of a projection of this nucleus to the hypothalamus, as also demonstrated in the present investigation, makes such a homology unlikely. We, therefore, interpret this nucleus as a brain structure of unknown homology in other teleosts and suggest 'nucleus G' to identify it.

Animals↗

PubMed1989

A quantitative histological study of the anterodorsal thalamic nucleus and the lateral mammillary nucleus of ageing mice.

The number of neurons and neuroglia in the anterodorsal nucleus of the thalamus and in the lateral mammillary nucleus of the ASH/TO strain mouse was estimated at 6, 25, 28 and 31 months of age. There was no significant variation in neuron number in either nucleus with age but there was a statistically significant increase (approximately 20%) in the number of neuroglia in the anterodorsal nucleus between 28 and 31 months of age which raised the glia to neuron ratio from 0.59 to 0.72. There was no change in neuroglial number in the ageing lateral mammillary nucleus. Neurons in both nuclei lost Nissl substance. This was first evident at 28 months in the anterodorsal nucleus and at 31 months in the lateral mammillary nucleus. Lipofuscin accumulation was common in the perikarya of anterodorsal nuclear neurons from 25 months onwards but was very rare in neurons of the lateral mammillary nucleus even at 31 months.

Aging↗

PubMed1986

[Changes in the activity of cells in the lateral geniculate nucleus by stimulation of the abducens nucleus area in rabbits].

These investigations are aimed at studying the influence of the electrical stimulation of the VIth nucleus (abducens nucleus) on responses of lateral geniculate cells in rabbits. The animals were prepared in the usual fashion for single cell recordings at the lateral geniculate nucleus (LGN). Results show that: Electrical stimulation of the VIth nucleus always produced excitatory discharges whose latency varied from 30 to 400 ms. Interestingly, an electrical pulse applied to the abducens nucleus was capable of enhancing the light-evoked responses without altering the spontaneous rate of firing. It thus seems that the ascending influence of the VIth nucleus manifests itself when it coincides with light responses. Most cells which were sensitive to electrical activation of the abducens nucleus had their receptive field located peripherally (greater than 50 degrees). Histological reconstructions of recording electrode tracts suggest that cells which responded to electrical stimulation were located in a narrow band lying dorsally relative to the LGN. This area can be paralleled with the perigeniculate area observed in other mammals, although not identified in rabbits. It is suggested that these extraretinal impulses which reach the LGN and emerge from an area surrounding the VIth nucleus are associated with corollary discharges.

Abducens Nerve↗

PubMed1995

Projections from the lateral mammillary nucleus to the anterodorsal thalamic nucleus in the rat.

There has been an abundance of research on the connections of the mammillary bodies but the projections from the lateral mammillary nucleus to the anterodorsal thalamic nucleus has remained a gray area due to a dearth of material which directly addresses the details of this pathway. This study seeks to further define the nature of this particular nerve connection within the mammillothalmic tract. The technique employed is fluorescent nerve tract tracing using two fluorescent tracers implanted separately into each anterodorsal thalamic nucleus then followed retrogradely to the soma of the neurons in the lateral mammillary nucleus. Fluorescent photomicrography allowed us to document the single and double labeled cells of the lateral mammillary nucleus. The single labeled cells can be categorized into ipsilaterally projecting neurons and contralaterally projecting neurons. About half of all labeled cells were bilaterally projecting double-labeled, a third was ipsilaterally projecting single-labeled and the remainder were contralaterally projecting single labeled-cells. There were no labeled cells traced to the medial mamillary nucleus. The mammillary bodies play an important role in the limbic circuitry and a part of the so-called "Papez Circuit". The pathway by which the mammillary body projects to the other structures of the limbic system and the way it connects the limbic system to other parts of the brain like the tegmentum is not fully understood. This clarification of the connection between the lateral mammilary nucleus and the anterodorsal thalamic nucleus is but one of the contemplated pathways.

Animals↗

PubMed1997

Innervation of the caudate nucleus, thalamus and red nucleus by the remaining sensorimotor cortex in cats with fetal or neonatal unilateral frontal cortex removal.

We studied the projections to the caudate nuclei, thalami and red nuclei from the remaining sensorimotor cortex in adult cats that had sustained a unilateral frontal cortex resection prenatally or neonatally. Four cats had the lesion at age E 50-55 and six animals sustained the ablation at age P 8-14 (seven cats were intact controls). All cats grew to young adulthood and then received injections of tritiated leucine-proline in the remaining sensorimotor cortex. Injection sites and axon terminal fields were reconstructed using autoradiography-processed tissue. In all cats the label filled a similar extent of the right pericruciate cortex. Terminal field densities in the subcortical nuclei were estimated using computer-based video software. Three medial-lateral sectors at five coronal levels were examined in the caudate nucleus. Three nuclear groups were analyzed in the thalamus (intralaminary, ventralis lateralis and ventrobasal complex). For the red nucleus, the four quadrants were examined at four coronal levels. The main goal of the study was to assess possible changes in the cortical innervation of the nuclei ipsilateral to the lesion. Therefore, the mean particle counts per nucleus (and per area or sector of nuclei) and per animal group were used to calculate percentage values for the decussated (crossed, or contralateral to the injection site) as a function of the non-decussated (uncrossed, or ipsilateral to the injection site) innervation. The percentage values for the crossed projections were: (a) for the entire caudate nucleus, 61.3% for the intact. 56.7% for the fetal-lesioned and 42.7% for the neonatal-lesioned cats, with no statistical differences between groups; (b) for the thalamus the proportion of crossed projections was minimal fluctuating between a low 0.06-0.16% for the nucleus ventralis lateralis and a high of 2.01-3.46% for the intralaminary nuclei, with the highest values belonging to the lesioned groups but with no significant differences between groups: (c) for the entire red nucleus, 1.98%, 12.74% (P < 0.05) and 6.76% for the intact, fetal- and neonatal-lesioned cats respectively. In the lesioned cats, the topography of the distribution of the axon terminals was bilaterally the same as in the controls. In conclusion, only the red nucleus of the frontal-lesioned cats showed an increased crossed innervation from the remaining sensorimotor cortex but this was relatively weak and statistically significant only for the fetal-lesioned animals. These results as well as the literature suggest that: (a) the crossed corticorubral projections in fetal cats may represent true reinnervation (i.e., newly originated, no preexisting terminals); (b) the relative paucity of the crossed projections in the present cats as compared to the extensive reorganization of subcortical terminals seen after cerebral hemispherectomy (our original postnatal lesion model) may be due to the much smaller size of the present cortical lesion which presumably induced only a limited amount of subcortical nuclear deafferentation.

Animals↗

PubMed1988

Projections of nucleus angularis and nucleus laminaris to the lateral lemniscal nuclear complex of the barn owl.

Interaural phase and intensity are cues by which the barn owl determines, respectively, the azimuth and elevation of a sound source. Physiological studies indicate that phase and intensity are processed independently in the auditory brainstem of the barn owl. The phases of spectral components of a sound are encoded in nucleus magnocellularis (NM), one of the two cochlear nuclei. NM projects solely and bilaterally to nucleus laminaris (NL), wherein interaural phase difference is computed. The other cochlear nucleus, nucleus angularis (NA), encodes the amplitudes of spectral components of sounds. We report here the projections of NA and NL to the lateral lemniscal nuclei of the barn owl. The lateral lemniscal complex comprises nucleus olivaris superior (SO); nucleus lemnisci lateralis, pars ventralis (LLv); and nucleus ventralis lemnisci lateralis (VLV). At caudal levels, VLV may be divided into a posterior (VLVp) and an anterior (VLVa) subdivision on cytoarchitectonic grounds. At rostral levels, the cytoarchitectural differences diminish and the boundaries between the two subdivisions become obscured. Likewise, our data from anterograde tracing studies suggest that at caudal levels the terminal fields of NA and NL remain confined to VLVp and VLVa, respectively. They merge, however, at rostral levels. The data also suggest that NL projects to the medial portion of the ipsilateral SO and that NA projects bilaterally to all parts of SO and LLv. Studies with the retrograde transport of horseradish peroxidase confirm these projections.

Afferent Pathways↗

PubMed1991

Thyrotropin-releasing hormone-immunoreactive projections to the dorsal motor nucleus and the nucleus of the solitary tract of the rat.

Thyrotropin-releasing hormone-immunoreactive nerve terminals heavily innervate the dorsal motor nucleus and nucleus of the solitary tract, whereas cell bodies containing thyrotropin-releasing hormone residue most densely in the hypothalamus and raphe nuclei. By using double-labeling techniques accomplished by retrograde transport of Fluoro-Gold following microinjection into the dorsal motor nucleus/nucleus of the solitary tract combined with immunohistochemistry for thyrotropin-releasing hormone, it was demonstrated that thyrotropin-releasing hormone-immunoreactive neurons projecting to the dorsal motor nucleus/nucleus of the solitary tract reside in the nucleus raphe pallidus, nucleus raphe obscurus, and the parapyramidal region of the ventral medulla, but not in the paraventricular nucleus of the hypothalamus. The parapyramidal region includes an area along the ventral surface of the caudal medulla, lateral to the pyramidal tract and inferior olivary nucleus and ventromedial to the lateral reticular nucleus. Varying the position of the Fluoro-Gold injection site revealed a rostral to caudal topographic organization of these raphe and parapyramidal projections.

Animals↗

PubMed1992

Regulation of nucleus accumbens dopamine release by the dorsal raphe nucleus in the rat.

The effects of microinfusing L-glutamate, serotonin (5-HT), (+-)-8-hydroxy-2-(di-N-propylamino) tetralin (8-OH DPAT; a 5-HT1A agonist), and muscimol (a GABAA agonist) into the dorsal raphe nucleus on the extracellular levels of 5-HT, dopamine (DA) and their metabolites in the nucleus accumbens were studied in unanesthetized, freely moving, adult male Wistar rats, using the technique of microdialysis coupled with small-bore HPLC. Administration of 0.75 micrograms L-glutamate produced a 25-50% increase (P less than 0.05) in the extracellular levels of both 5-HT and DA. On the other hand, infusion of 8-OH DPAT and, to a lesser extent, 5-HT produced a significant (P less than 0.05) decrease in the extracellular levels of both 5-HT and DA. Muscimol (0.25 or 0.50 microgram) had little effect on the extracellular concentrations of 5-HT or DA following its administration. In general, the extracellular levels of the major metabolites of 5-HT and DA in the nucleus accumbens were not altered by microinfusion of any of the agents. The data indicate that (a) the 5-HT neurons projecting to the nucleus accumbens from the dorsal raphe nucleus can be activated by excitatory amino acid receptors and inhibited by stimulation of 5-HT1A autoreceptors, and (b) the dorsal raphe nucleus 5-HT neuronal system may regulate the ventral tegmental area DA projection to the nucleus accumbens.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2004

Onset neurones in the anteroventral cochlear nucleus project to the dorsal cochlear nucleus.

Considerable circumstantial evidence suggests that cells in the ventral cochlear nucleus, that respond predominantly to the onset of pure tone bursts, have a stellate morphology and project, among other places, to the dorsal cochlear nucleus. The characteristics of such cells make them leading candidates for providing the so-called "wideband inhibitory input" which is an essential part of the processing machinery of the dorsal cochlear nucleus. Here we use juxtacellular labeling with biocytin to demonstrate directly that large stellate cells, with onset responses, terminate profusely in the dorsal cochlear nucleus. They also provide widespread local innervation of the anteroventral cochlear nucleus and a small innervation of the posteroventral cochlear nucleus. In addition, some onset cells project to the contralateral dorsal cochlear nucleus.

Animals↗

PubMed1990

Topographical projections from the thalamus, subthalamic nucleus and pedunculopontine tegmental nucleus to the striatum in the Japanese monkey, Macaca fuscata.

Topographical projections from the thalamus, subthalamic nucleus (STN) and pedunculopontine tegmental nucleus (PPN) to the striatum were examined in the Japanese monkey (Macaca fuscata) by using the retrograde axonal transport technique of WGA-HRP (wheat germ agglutinin-conjugated horseradish peroxidase). After WGA-HRP injection in the head of the caudate nucleus (CN) or putamen (Put), labeled neuronal cell bodies in the thalamus were distributed mainly in the nucleus ventralis anterior (VA)-nucleus ventralis lateralis (VL) complex and the nucleus centrum medianum (CM)-nucleus parafascicularis (Pf) complex, and additionally in the paraventricular, parataenial, rhomboid, reuniens, centrodorsal, centrolateral, paracentral, and centromedial nuclei. The data indicated that the pars principalis of VA (VApc) projected mainly to CN and additionally to Put, and that the pars magnocellularis of VA (VAmc) or pars oralis of VL (VLo) projected selectively to CN or Put, respectively. It was also indicated that CM projected to the middle and caudal parts of Put, while Pf projected to CN and the rostral part of the Put. The data further indicated that the dorsomedial, ventromedial, or lateral part of CM projected respectively to the dorsolateral, ventromedial, or intermediate part of Put, and that the medial or lateral part of Pf projected respectively to the medial or lateral part of the head of CN. Direct projections from STN and PPN to the striatum were confirmed. The subthalamostriatal projections showed a mediolateral topography. The PPN was shown to project bilaterally to the striatum with an ipsilateral predominance.

Animals↗

PubMed1990

Effects of lidocaine injection in the interpositus nucleus and red nucleus on conditioned behavioral and neuronal responses.

The role of the cerebellum and the red nucleus in the conditioned eyeblink response was assessed, using a combination of reversible lesions and multiple-unit extracellular recording in the awake, behaving rabbit. Lesion, recording, and stimulation experiments have indicated that both of these structures are involved in the performance of learned skeletal muscle responses. The present study sought to distinguish the relative contributions of the interpositus nucleus and the red nucleus to the expression of the learned response by recording behavior-related multiple unit activity in one structure while reversibly inactivating the other via injections of local anesthetic. Results indicate that inactivating either the interpositus or the red nucleus temporarily abolishes the learned eyeblink response. Injection of lidocaine into the interpositus also abolishes the neuronal unit model of the conditioned response in the red nucleus, while injection into the red nucleus does not affect the model in the interpositus. These results are consistent with the hypothesis that the red nucleus acts as a relay for motor commands from the cerebellum, and that the plasticity that generates conditioned responses occurs in the cerebellum or an afferent structure.

Animals↗

PubMed2004

Kynurenate in the pontine reticular formation inhibits acoustic and trigeminal nucleus-evoked startle, but not vestibular nucleus-evoked startle.

The startle reflex is elicited by acoustic, trigeminal or vestibular stimulation, or by combinations of these stimuli. Acoustic startle is mediated largely by ibotenate-sensitive neurons in the ventrocaudal pontine reticular formation (PnC). In these studies we tested whether startle elicited by stimulation of different modalities is affected by infusion of the non-selective glutamate antagonist, kynurenate, into the PnC. In awake rats, startle responses evoked by either acoustic or spinal trigeminal nucleus stimulation were inhibited by kynurenate, but not saline, infusions, with the most effective placements nearest PnC. In chloral hydrate-anesthetized rats, kynurenate in the PnC reduced trigeminal nucleus-evoked hindlimb EMG responses, but not vestibular nucleus-evoked startle. Kynurenate in the vestibular nucleus had no effect on trigeminal nucleus-evoked startle. These results indicate that trigeminal nucleus stimulation evokes startle largely through glutamate receptors in the PnC, similarly to acoustic startle, but vestibular nucleus-evoked startle is mediated through other pathways, such as the vestibulospinal tract.

Animals↗

PubMed2000

Effect of high-frequency stimulation of the subthalamic nucleus on the neuronal activities of the substantia nigra pars reticulata and ventrolateral nucleus of the thalamus in the rat.

Electrophysiological recordings were made in anaesthetized rats to investigate the mode of function of high-frequency stimulation of the subthalamic nucleus used as a therapeutic approach for Parkinson's disease. High-frequency electrical stimulation of the subthalamic nucleus (130 Hz) induced a net decrease in activity of all cells recorded around the site of stimulation in the subthalamic nucleus. It also caused an inhibition of the majority of neurons recorded in the substantia nigra pars reticulata in normal rats (94%) and in rats with 6-hydroxydopamine lesions of the substantia nigra pars compacta (90%) or with ibotenic acid lesions of the globus pallidus (79.5%). The majority of cells recorded in the ventrolateral nucleus of the thalamus responded with an increase in their activity (84%). These results show that high-frequency stimulation of the subthalamic nucleus induces a reduction of the excitatory glutamatergic output from the subthalamic nucleus which results in deactivation of substantia nigra pars reticulata neurons. The reduction in tonic inhibitory drive of nigral neurons induces a disinhibition of activity in the ventrolateral motor thalamic nucleus, which should result in activation of the motor cortical system.

Adrenergic Agents↗