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PubMed1986

Differences in function and structure of the capillary endothelium in the supraoptic nucleus and pituitary neural lobe of rats. Evidence for the supraoptic nucleus as an osmometer.

The physiology and structure of capillary endothelial cells in the hypothalamic ventromedial and supraoptic nuclei and pituitary neural lobe were evaluated with quantitative methods and compared. The capillary endothelial cells in the ventromedial nucleus were used as an index of blood-brain barrier endothelium in cerebral gray matter; this endothelium has relatively low surface area and low permeability to tracer solutes. The permeability X surface area product of endothelial cells for a neutral amino acid, 14C-alpha-aminoisobutyric acid (AIB), in the ventromedial nucleus was similar to the value for supraoptic nucleus and was several hundred times smaller than in the neural lobe. The supraoptic nuclei and neural lobe had exceptionally large capillary surface areas, but dissimilar rates of blood flow and transendothelial influx of AIB. Differences in permeability of the endothelial cells between these two structures correlated closely with their marked dissimilarities in morphology. The neural lobe endothelium had numerous fenestrations (five per capillary cross-section) and vesicular profiles (twice as many as supraoptic nucleus), two features commonly associated with high capillary permeability. The capillary endothelium of the supraoptic nucleus was that of a typical blood-brain barrier structure having intercellular junctions that appeared tight, no fenestrations, and few cytoplasmic pits and vesicles. The unusually large capillary surface area of the supraoptic nucleus and low rate of solute flux across its endothelial cells make this nucleus a unique structure in which rapid changes in tissue volume may occur in response to small perturbations in plasma osmolality. The findings implicate the supraoptic nucleus as an osmotically sensitive detector or 'osmometer' in neuroendocrine regulation of body fluid homeostasis.

Animals↗

PubMed1996

Mossy fiber projections from the cuneate nucleus to the cochlear nucleus in the rat.

A reciprocal connection is known to exist between the cuneate nucleus, which is a first-order somatosensory nucleus, and the cochlear nucleus, which is a first-order auditory nucleus. We continued this line of study by investigating the fiber endings of this projection in the cochlear nucleus of rats using the neuronal tracer Phaseolus vulgaris leucoagglutinin in combination with ultrastructural and immunocytochemical analyses. In the cochlear nucleus, mossy fiber terminals had been described and named for their morphologic similarity to those in the cerebellum, but their origins had not been discovered. In the present study, we determined that the axonal projections from the cuneate region gave rise to mossy fiber terminals in the granule cell regions of the ipsilateral cochlear nucleus. The cuneate mossy fibers appear to be excitatory in nature, because they are filled with round synaptic vesicles, they make asymmetric synapses with postsynaptic targets, and they are labeled with an antibody to glutamate. The postsynaptic targets of the mossy fibers include dendrites of granule cells. This projection onto the granule cell interneuron circuit of the cochlear nucleus indicates that somatosensory cues are intimately involved with information processing at this early stage of the auditory system.

Animals↗

PubMed1991

Projections from the subfornical organ to the supraoptic nucleus in the rat: ultrastructural identification of an interposed synapse in the median preoptic nucleus using a combination of neuronal tracers.

The subfornical organ, along with other regions of the lamina terminalis, may contain osmoreceptors and is likely to be a site of action of blood-borne angiotensin II. The neural pathways by which these stimuli lead to vasopressin secretion, have been suggested to extend from the subfornical organ to hypothalamic sites of vasopressin production either directly or via synapses in an intervening nucleus such as the median preoptic nucleus. In the present study, cholera toxin conjugated to horseradish peroxidase (CT/HRP) or colloidal gold (CT/Au) has been injected, respectively, into the subfornical organ and supraoptic nucleus of the same animal. The anterograde and retrograde transport of the toxin from these two sites has made possible the identification, at the ultrastructural level, of a synapse in the median preoptic nucleus interposed in the pathway between the subfornical organ and the supraoptic nucleus. Moreover, the presence of retrogradely transported CT/HRP and CT/Au in the same neurone in the median preoptic nucleus indicates that some neurones in this nucleus have axons with collateral branches to both the subfornical organ and supraoptic nucleus. Either or both of these pathways may transmit information related to the tonicity of the blood or circulating levels of angiotensin II to sites in the hypothalamus.

Animals↗

PubMed1992

Testosterone regulates substance P within neurons of the medial nucleus of the amygdala, the bed nucleus of the stria terminalis and the medial preoptic area of the male golden hamster.

The medial nucleus of the amygdala, bed nucleus of the stria terminalis, and medial preoptic area appear to mediate steroidal regulation of mating behavior in male rodents. The mechanism of action has not been determined. One way testosterone could enhance neuronal function is by increasing neurotransmitter levels, thus altering neuronal transmission. To assess this hypothesis, we examined the effect of castration and testosterone treatment on substance P levels in the neurons of these three brain regions. Brains from male Syrian hamsters that were (1) gonadally intact, (2) castrated for 13 weeks, or (3) castrated for 9 weeks and treated with testosterone for 4 weeks, were processed for substance P, and the numbers of substance P immunoreactive neurons in the medial nucleus of the amygdala, bed nucleus of the stria terminalis, and medial preoptic area were determined. Castration reduced the number of substance P neurons in the bed nucleus of the stria terminalis and medial preoptic area relative to those in intact hamsters; the number of substance P neurons in these regions was restored by testosterone treatment. Castration did not reduce the number of substance P neurons in the medial nucleus of the amygdala; however, testosterone treatment increased the numbers of these neurons when compared to intacts. Thus, testosterone regulates substance P levels in areas that regulate mating behavior. As substance P enhances male copulatory behavior our results suggest that testosterone may regulate copulatory behavior by enhancing substance P levels in medial nucleus of the amygdala, bed nucleus of the stria terminalis and medial preoptic area.

Amygdala↗

PubMed1987

Anatomical evidence of a reciprocal connection between the posterior thalamic nucleus and the parvocellular division of the red nucleus in the rat. A combined retrograde and anterograde study.

The functional and anatomical organizations of the magnocellular part of the red nucleus are now well established. Our knowledge of the parvocellular part is, however, more limited. Using both anterograde and retrograde tracing methods, the present study suggests in the rat the existence of a large projection from the posterior thalamic nucleus to the parvocellular part of the red nucleus. In turn, the parvocellular part of the red nucleus sends a weaker projection to the posterior thalamic nucleus. Three different tracers were utilized (horseradish peroxidase alone, horseradish peroxidase conjugated to wheat germ agglutinin and Phaseolus vulgaris leucoagglutinin), all of which gave similar results. The posterior thalamic nucleus is known to receive a large proportion of somatosensory afferents. It is suggested, therefore, that in addition to receiving cerebellar and cortical inputs, the parvocellular part of the red nucleus has access to highly integrated somatosensory and/or nociceptive information delivered by the posterior thalamic nucleus.

Animals↗

PubMed1987

Hippocampal signal transmission to the pedunculopontine nucleus and its regulation by dopamine D2 receptors in the nucleus accumbens: an electrophysiological and behavioural study.

The integrative role of the nucleus accumbens and subpallidal area in relaying hippocampal signals to the mesencephalic locomotor region in the brainstem was investigated electrophysiologically in urethan-anaesthetized rats. A behavioural study of the functional connections was also performed in freely moving rats. In the electrophysiological experiments, subpallidal output neurons to the pedunculopontine nucleus and the adjacent ventral gray were first identified by their antidromic responses to electrical stimulation of the pedunculopontine nucleus. Hippocampal stimulation was then shown to inhibit orthodromically some of these subpallidal neurons. The inhibitory response was attenuated following microinjection of a dopamine D2 agonist (LY 171555), but not a D1 agonist (SKF 38393), into the accumbens. This suggests that signal transmission from the hippocampus to the subpallidal output neurons to the pedunculopontine nucleus is modulated by a D2 receptor-mediated mechanism in the nucleus accumbens. Injections of N-methyl-D-aspartate into the ventral subiculum of the hippocampus resulted in a threefold increase in locomotor responses. Injection of a D2 agonist into the accumbens reduced the hyperkinetic response dose-dependently and suggests that D2 receptors regulate locomotor responses initiated by the hippocampal-accumbens pathway. Injection of nipecotic acid, a GABA uptake inhibitor, into the subpallidal area or of procaine, a neural transmission blocker, into the region of the pedunculopontine nucleus, also reduced significantly the hippocampal-induced hyperkinetic response. These results provide evidence of limbic (e.g. hippocampus) influences on locomotor activity by way of nucleus accumbens-subpallidal-pedunculopontine nucleus connections which may contribute to adaptive behaviour. Signal transmission from the hippocampus may be regulated by a dopamine D2 receptor mechanism in the accumbens, presumably mediated by the converging mesolimbic dopaminergic input from the ventral tegmental area.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1990

The role of serotonin release and autoreceptors in the dorsalis raphe nucleus in the control of serotonin release in the cat caudate nucleus.

Using a push-pull cannula technique and an isotopic method for estimating [3H]serotonin continuously synthesized from [3H]tryptophan, the effects of changes in the release of serotonin in the dorsalis raphe nucleus on in vivo release of [3H]serotonin in the cat caudate nucleus were investigated. The increase in the release of serotonin in the dorsalis raphe nucleus caused by local application of parachlorophenylethylamine (10(-6) M) reduced striatal [3H]serotonin release. This inhibition in serotonin release in the striatum was blocked by the prior and continuous local superfusion of the dorsal raphe with methiothepin (10(-6) M), a serotonin autoreceptor antagonist. GABA (5 x 10(-5) M) applied to the dorsalis raphe reduced both local and striatal release of [3H]serotonin. However, picrotoxin (10(-5) M), a GABA A receptor antagonist applied locally in the dorsalis raphe nucleus increased [3H]serotonin release while decreasing striatal [3H]serotonin release. This decrease in serotonin release in the striatum was again blocked by continuous superfusion of the raphe with methiothepin. Furthermore, superfusion of serotonergic cell bodies of the dorsalis raphe nucleus with methiothepin alone never altered local release or striatal release of [3H]serotonin. These data strongly suggest that the release of serotonin from the cell body in the dorsalis raphe nucleus phasically controls release of the amine at the axonal nerve ending through serotonergic autoreceptors located on serotonergic nerve cell bodies in the dorsalis raphe nucleus. The origin of the serotonin released in the dorsalis raphe nucleus and the possibility that this type of regulation could be related to changes in nerve impulse conduction of the serotonergic raphe-striatal system are discussed.

Animals↗

PubMed1996

Projections from the ventral cochlear nucleus to the inferior colliculus and the contralateral cochlear nucleus in guinea pigs.

Multipolar cells in the ventral cochlear nucleus are the source of projections to numerous brainstem auditory nuclei, including the contralateral and ipsilateral inferior colliculi and the contralateral cochlear nucleus. Multiple fluorescent tracers were used to label the multipolar cells that project to each of these targets. Following injections of different tracers into each target, the ventral cochlear nucleus was examined for the presence of cells that contained more than one tracer. Such cells were never observed. In contrast, double-labeled cells were common in the dorsal cochlear nucleus, where cells frequently contained the two tracers that were injected into the ipsilateral and contralateral inferior colliculi. The distribution and somatic morphology of cells in the ventral cochlear nucleus that project to each of the three targets were examined. Each population contained cells with somas that ranged in shape from elongated to rounded, but there were differences in soma size. Projections to the ipsilateral and contralateral inferior colliculi arise predominantly from small to medium-sized cells, the average size being slightly less for cells with projections to the ipsilateral colliculus. Projections to the contralateral cochlear nucleus arise from cells with somas that range in size from small to large, including cells much larger than those that projected to either inferior colliculus. On the basis of these results, we conclude that projections from the ventral cochlear nucleus to the ipsilateral and contralateral inferior colliculi and to the contralateral cochlear nucleus arise in three different populations of multipolar cells.

Analysis of Variance↗

PubMed2001

Fine structure and neurotransmitter cytochemistry of neurons in the rat ventral cochlear nucleus projecting to the ipsilateral dorsal cochlear nucleus.

The neural tracer wheat germ agglutinin conjugated to horse radish peroxidase was injected into the rat dorsal cochlear nucleus and acoustic stria. Some labelled neurons in the ipsilateral ventral cochlear nucleus were found as a result. These neurons were studied at the ultrastructural level, and their axo-somatic synaptic profile and glycine immunoreactivity were determined. Most neurons were glycine negative and classified as type I multipolar neurons. The latter showed a different synaptic profile from that of neurons projecting to the contralateral inferior colliculus or cochlear nucleus. This suggests the presence of differing populations of multipolar cells based on their synaptic profile. Few labelled multipolar neurons of type II were found, which appeared glycine negative and, rarely, glycine positive. The latter show an ultrastructure and axo-somatic profile similar to that of glycinergic commissural neurons in the dorsal and ventral cochlear nucleus. In particular, about one-third of boutons contained round synaptic vesicles, which are believed to contain an excitatory neurotransmitter. The ultrastructural analysis of the synaptic boutons in the cochlear nucleus confirms the presence of numerous cases of colocalization of glycine and GABA where flat and pleomorphic synaptic vesicles are mixed. The present study is in accordance with previous tract-tracing light microscopic studies which have indicated that large glycinergic neurons in the ventral cochlear nucleus act as broad-band inhibitory neurons in microcircuits of the dorsal cochlear nucleus and contralateral cochlear nucleus.

Animals↗

PubMed1999

Glycine immunoreactivity of multipolar neurons in the ventral cochlear nucleus which project to the dorsal cochlear nucleus.

Certain distinct populations of neurons in the dorsal cochlear nucleus are inhibited by a neural source that is responsive to a wide range of acoustic frequencies. In this study, we examined the glycine immunoreactivity of two types of ventral cochlear nucleus neurons (planar and radiate) in the rat which project to the dorsal cochlear nucleus (DCN) and thus, might be responsible for this inhibition. Previously, we proposed that planar neurons provided a tonotopic and narrowly tuned input to the DCN, whereas radiate neurons provided a broadly tuned input and thus, were strong candidates as the source of broadband inhibition (Doucet and Ryugo [1997] J. Comp. Neurol. 385:245-264). We tested this idea by combining retrograde labeling and glycine immunohistochemical protocols. Planar and radiate neurons were first retrogradely labeled by injecting biotinylated dextran amine into a restricted region of the dorsal cochlear nucleus. The labeled cells were visualized using streptavidin conjugated to indocarbocyanine (Cy3), a fluorescent marker. Sections that contained planar or radiate neurons were then processed for glycine immunocytochemistry using diaminobenzidine as the chromogen. Immunostaining of planar neurons was light, comparable to that of excitatory neurons (pyramidal neurons in the DCN), whereas immunostaining of radiate neurons was dark, comparable to that of glycinergic neurons (cartwheel cells in the dorsal cochlear nucleus and principal cells in the medial nucleus of the trapezoid body). These results are consistent with the hypothesis that radiate neurons in the ventral cochlear nucleus subserve the wideband inhibition observed in the dorsal cochlear nucleus.

Animals↗

PubMed2004

The spinal trigeminal nucleus--considerations on the structure of the nucleus caudalis.

The caudal part (nucleus caudalis) of the spinal trigeminal nucleus is considered to be the site of the second order neurons of the nociceptive pathways of the face. Recent studies have supported the co-participation in these circuits of the oral part of the same nucleus (nucleus oralis). The aims of the present study are: 1) to determine the morphology of the nucleus caudalis in human preparates; 2) to consider whether there is any structural basis for the pathways of signal transmission observed in animal experiments; 3) to provide evidence-based support for further consideration on the orofacial pathways. The studies were made using the Bielschowsky silver staining technique (on blocks) applied to drawn pieces of brainstems from human cadavers. On the sections the outer laminae of the nucleus are distinguishable, while the inner part hardly exposes any laminar configuration on transverse cuts. A marginal plexus with small polygonal or rounded small cells appears configured in 3 parts, namely dorsal, intermediate and ventral. Outer to the marginal plexus a clear band marks it off from the interstitial plexus, which appears more delicate. Within the marginal plexus is substantia gelatinosa with rare randomly distributed small or medium-sized cells. The inner magnocellular layers consist of clusters of small cells specifically allocated to fibre bundles, isolated small cells and large cells, pear-shaped or fusiform, appearing either bipolar or multipolar. The marginal and interstitial plexuses can represent the framework for modulation and vertical signal transmission within the spinal trigeminal nucleus, while the magnocellular layers seem to be mainly responsible for contralateral projection. It seems that the outer laminae of the spinal trigeminal nucleus may represent the receiver and the inner laminae the transmitter of the signal on the trigeminal pathway at brainstem level.

Animals↗

PubMed1981

The ascending projection of the nucleus of the lateral descending trigeminal tract: a nucleus in the infrared system of the rattlesnake, Crotalus viridis.

The efferent projections of the nucleus of the lateral descending trigeminal tract (LTTD) in the rattlesnake (Crotalus viridis) were studied by anterograde tracing techniques. The LTTD, a brainstem trigeminal nucleus, is the sole projection site of the infrared-sensitive trigeminal fibers that innervate the pit organs in these snakes. The efferent fibers exit from the ventromedial edge of the LTTD and course medially and caudally toward the central grey area of the medulla. Upon reaching the central region of the medulla these fibers turn and move laterally and rostrally, eventually forming a tract on the ventrolateral surface of the brainstem. Embedded in this tract and slightly overlapping the LTTD in the rostrocaudal axis, is a population of large (20-45 micrometer) multipolar neurons that forms the nucleus reticularis caloris. Heavy terminal and preterminal degeneration in this area indicates that many of the efferent fibers of the LTTD terminate in this nucleus. A small bundle of degenerating fibers turn dorsally from the ventrolateral tract and ascend to terminate in a nucleus associated with the cerebellum, the lateral tegmental nucleus. No projection was found to any other nuclei or areas in the brain. This study demonstrates that the infrared-sensitive snakes, along with developing peripheral specializations (the pit organs), have developed specialized nuclei to handle this additional sensory information. The direct projection from the LTTD to the nucleus reticularis caloris provides a pathway linking the infrared-sensitive neurons of the LTTD with neurons of the same modality in the optic tectum. The second LTTD projection, to the lateral tegmental nucleus, suggests a connection between the infrared system and the cerebellum in these animals.

Animals↗

PubMed1982

Organization of nucleus rotundus, a tectofugal thalamic nucleus in turtles. III. The tectorotundal projection.

Nucleus rotundus is the primary thalamic recipient of projections from the optic tectum in pond turtles. Although the projection of the retina to the optic tectum is known to be topographically organized, earlier studies suggest that the tectorotundal projection is not topographically organized. Three types of analyses are used in this paper to characterize the organization of the projection of the optic tectum to nucleus rotundus. First, large iontophoretic injections of horseradish peroxidase into the optic tectum anterogradely fill axons with reaction product after the use of a cobalt-enhanced diaminobenzidine procedure. These preparations show that shafts of axons in the tectothalamic tract give rise to thinner, primary collaterals that enter nucleus rotundus from its caudolateral aspect and form sparsely branching arbors within the nucleus. Very thin secondary collaterals branch from these collateral bear terminal collaterals with frequent varicosities. Although the total size of such arbors is unknown, the evidence suggests that each arbor is large in relation to the size of nucleus rotundus. Thus, injection sites restricted to central tectum label axons throughout nucleus rotundus. Second, subtotal lesions of the tectum produce degeneration throughout nucleus rotundus in silver degeneration preparations. Finally, analysis of electron microscopic degeneration material indicates that tectal boutons are distributed along the full lengths of the dendrites of rotundal neurons, but not on their somata. These boutons form asymmetric synaptic junctions and contain round synaptic vesicles. In view of the relatively large size of the dendritic fields of rotundal neurons, these data suggest that the tectorotundal projection is both strongly convergent on individual neurons and strongly divergent from single tectorotundal axons. This type of organization is consistent with physiological evidence that rotundal neurons have receptive fields that cover at least one-half of the contralateral visual field and often include the entire hemifield. It seems unlikely that nucleus rotundus can be involved in neuronal transactions that preserve detailed spatial information, but it may be involved in processing information on other visual parameters such as stimulus velocity or color.

Animals↗

PubMed1983

Fine structure and organization of the infrared receptor relays: lateral descending nucleus of V in Boidae and nucleus reticularis caloris in the rattlesnake.

The morphology of the lateral descending nucleus of V (LTTD) in three species of Boidae and nucleus reticularis caloris (RC) of the rattlesnake have been studied with the light and electron microscope. First- and second-order relays in the infrared receptor pathway to the tectum are contained within LTTD in the Boidae, whereas in the rattlesnakes the secondary relay to tectipetal neurons is in nucleus RC. The lateral descending nucleus in the boids contains small and large neurons. The larger cells project to the optic tectum and morphologically are quite similar to those of nucleus RC. It has been determined at the ultrastructural level that LTTD of the three species of boids studied have very similar morphology and organization. A marginal neuropil, located near the lateral descending tract, consists of terminals of thin unmyelinated axons in synaptic contact with thin dendrites. Deeper within the nucleus primary afferent terminals containing clear spherical vesicles form synaptic clusters with dendrites and are post-synaptic to other axon terminals containing pleomorphic vesicles. The large, tectipetal neurons are postsynaptic to two morphological types of synapses, one with clear spherical vesicles, asymmetric membranes, and subsynaptic web and the other with flattened vesicles and symmetrical membranes. Similar synapses are also present on the cells of nucleus RC in the rattlesnake. There is a close similarity in function, structure, and synaptic organization between the LTTD and boids and the LTTD plus nucleus RC of pit vipers, suggesting similar or identical evolutionary origin.

Animals↗

PubMed1992

GABAergic and non-GABAergic projections of accessory optic nuclei, including the visual tegmental relay zone, to the nucleus of the optic tract and dorsal terminal accessory optic nucleus in rat.

This study examines the non-gamma-amino butyric acid (GABA)ergic (group I neurons) and GABAergic neurons (group II neurons) of the accessory optic system projecting to the nucleus of the optic tract (NOT)/dorsal terminal nucleus (DTN) of the accessory optic system in rat. These nuclei include the dorsal (MTNd) and ventral (MTNv) divisions of the medial terminal nucleus, the lateral terminal nucleus, the interstitial nucleus of the superior fasciculus, the posterior fibers, and the visual tegmental relay zone. GABAergic neurons of these nuclei that do not target the NOT/DTN (group III neurons) have also been observed. The fluorescent retrograde tracer fluoro-gold was injected into the pretectum, targeting the NOT/DTN and the tissue prepared immunocytochemically to reveal neurons containing the neurotransmitter GABA. Three groups of neurons (groups I, II, and III neurons) were examined in terms of their distribution, density, and percentage present. Group I neurons are single-labeled with fluoro-gold and represent non-GABAergic neurons projecting to the NOT/DTN. These neurons are of the highest density in the lateral terminal nucleus (204 neurons/mm2). Their densities are also substantial in the MTNv (120 neurons/mm2), interstitial nucleus of the superior fasciculus, posterior fibers (96 neurons/mm2), and visual tegmental relay zone (93 neurons/mm2). Group II neurons are double-labeled with fluoro-gold and GABA. They form a system of GABAergic neurons projecting to the NOT/DTN, which are exceedingly dense in the MTNd (78 neurons/mm2) but are also dense in both the visual tegmental relay zone (49 neurons/mm2) and MTNv (33 neurons/mm2). Group III neurons are GABAergic neurons that do not target the NOT/DTN but must project to other brain nuclei and/or be interneurons. These are of extremely high concentration in the visual tegmental relay zone (316 neurons/mm2) and are also of substantial densities in the MTNd (77 neurons/mm2), lateral terminal nucleus (72 neurons/mm2), and MTNv (44 neurons/mm2). The MTNd has the highest percentage of GABAergic neurons projecting to the NOT/DTN (72%). GABAergic neurons also form significant percentages of the projections to the NOT/DTN from the visual tegmental relay zone (34%) and MTNv (21%). The percentage of the total GABAergic neurons that project to the NOT/DTN is the highest in the MTNd (50%) and MTNv (42%). The described GABAergic afferents to the NOT/DTN may function to process information concerned with the compensation for retinal slip.

Animals↗

PubMed1992

Cholinergic innervation of the human striatum, globus pallidus, subthalamic nucleus, substantia nigra, and red nucleus.

The anatomical organization of cholinergic markers such as acetylcholinesterase, choline acetyltransferase, and nerve growth factor receptors was investigated in the basal ganglia of the human brain. The distribution of choline acetyltransferase-immunoreactive axons and varicosities and their relationship to regional perikarya showed that the caudate, putamen, nucleus accumbens, olfactory tubercle, globus pallidus, substantia nigra, red nucleus, and subthalamic nucleus of the human brain receive widespread cholinergic innervation. Components of the striatum (i.e., the putamen, caudate, olfactory tubercle, and nucleus accumbens) displayed the highest density of cholinergic varicosities. The next highest density of cholinergic innervation was detected in the red nucleus and subthalamic nucleus. The level of cholinergic innervation was of intermediate density in the globus pallidus and the ventral tegmental area and low in the pars compacta of the substantia nigra. Immunoreactivity for nerve growth factor receptors (NGFr) was confined to the cholinergic neurons of the basal forebrain and their processes. Axonal immunoreactivity for NGFr was therefore used as a marker for cholinergic projections originating from the basal forebrain (Woolf et al., '89: Neuroscience 30:143-152). Although the vast majority of striatal cholinergic innervation was NGFr-negative and, therefore, intrinsic, the striatum also contained NGFr-positive axons, indicating the existence of an additional cholinergic input from the basal forebrain. This basal forebrain cholinergic innervation was more pronounced in the putamen than in the caudate. The distribution of NGFr-positive axons suggested that the basal forebrain may also project to the globus pallidus but probably not to the subthalamic nucleus, substantia nigra, or red nucleus. The great majority of cholinergic innervation to these latter three structures and to parts of the globus pallidus appeared to come from cholinergic neurons outside the basal forebrain, most of which are probably located in the upper brainstem. These observations indicate that cholinergic neurotransmission originating from multiple sources is likely to play an important role in the diverse motor and behavioral affiliations that have been attributed to the human basal ganglia.

Acetylcholinesterase↗

PubMed1995

Convergent influence of the central nucleus of the amygdala and the paraventricular hypothalamic nucleus upon brainstem autonomic neurons as revealed by c-fos expression and anatomical tracing.

Combinations of anatomical tracing with detection of Fos (the protein product of the immediate early gene c-fos) consequent to the stimulation of the central nucleus of the amygdala were used to explore the possibility that the hypothalamic paraventricular nucleus participates in the activation of brainstem neurons in the nucleus of the solitary tract and ventrolateral medulla. After injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin in the paraventricular nucleus, labeled fibers and varicosities were found to impinge on catecholaminergic and non-catecholaminergic Fos-positive neurons in the brainstem. After injections of a retrograde tracer in the nucleus of the solitary tract or ventrolateral medulla, we observed that some of the Fos-positive neurons within the parvocellular paraventricular nucleus that project to the brainstem were catecholaminergic or oxytocinergic. The results indicate that direct and indirect inputs from the amygdala may influence the activity of autonomic neurons in the brainstem. The paraventricular nucleus, via its direct projections onto catecholaminergic and non-catecholaminergic neurons, may participate in activation of brainstem neurons. Activated catecholaminergic and oxytocinergic parvocellular neurons in the paraventricular nucleus may be involved in the transmission of autonomic signals from the amygdala toward the brainstem.

Amygdala↗

PubMed1991

Demonstration of projections from the lateral nucleus to the basal nucleus of the amygdala: a PHA-L study in the monkey.

Previous studies of the intrinsic connections of the amygdaloid complex in the rat, cat and monkey demonstrated that the lateral nucleus projects prominently to the accessory basal nucleus and periamygdaloid cortex and lightly to several other nuclei of the amygdala. Most previous studies have emphasized the lack of a connection between the lateral and basal nuclei. As part of ongoing studies of the intrinsic circuitry of the monkey amygdala, we have placed discrete, iontophoretic injections of the lectin anterograde tracer Phaseolus vulgaris leucoagglutinin into the lateral nucleus of the Macaca fascicularis monkey. In addition to confirming the well established intrinsic connections of the lateral nucleus, heavy fiber and terminal labeling was also observed in the adjacent basal nucleus. The projection innervated all divisions of the basal nucleus and tended to be somewhat denser rostral to the level of the injection site. This hitherto unreported intrinsic connection provides a means by which the lateral nucleus, which is the principal recipient of afferents from sensory neocortex, can influence cells of the basal nucleus, which originate the major amygdalofugal projection to the neocortex.

Amygdala↗