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At least 433 records · Page 24Linked to original sources
PubMed1990

Calcitonin gene-related peptide (CGRP) immunoreactivity in the afferents to the caudate-putamen and perirhinal cortex of rats.

The posterior caudate-putamen and perirhinal cortex are innervated by fibers immunoreactive to calcitonin gene-related peptide (CGRP). We investigated the origins of these fibers by using immunohistochemistry combined with lesion experiments and fluorescent dye tracers. Lesions of the posterior thalamus surrounding the medial geniculate nucleus, in which groups of CGRP-like immunoreactive (CGRP-LI) cells exist, decreased the number of ipsilaterally CGRP-LI fibers in the posterior caudate-putamen and partly in the perirhinal cortex. Some of CGRP-LI neurons in several posterior thalamic nuclei surrounding the medial geniculate nucleus were labeled with both Fast blue injected into the posterior caudate-putamen and fluoro-gold administered into the anterior perirhinal cortex. Our results indicate that CGRP-LI cells in the posterior thalamus, such as posterior intralaminar, lateral subparafascicular and subparafascicular nuclei, project either separately or simultaneously to innervate the posterior caudate-putamen and perirhinal cortex.

Amidines↗
PubMed1990

Tectospinal neurons in hamster contain glutamate-like immunoreactivity.

Immunocytochemistry with a monoclonal antibody directed against glutamate revealed numerous immunoreactive cells in the hamster's superior colliculus (SC). A large number of these neurons were located in the deep layers and many were in the stratum album intermedium (SAI). These neurons appeared similar to the large multipolar cells that have been shown to project to the cervical spinal cord in this species. The combination of retrograde tracing using either Fluoro-Gold- or FITC-labelled latex beads with immunocytochemistry for glutamate revealed that many of the immunoreactive cells did, in fact, project into the predorsal bundle and extend axons as far as the cervical spinal cord.

Animals↗
PubMed1990

Long-term retrograde labelling of neurons.

The intensity of labelling of neuronal perikarya with Fluoro-gold or rhodamine microspheres appeared unchanged in rats surviving one year after surgery. These tracers may be used for sequential labelling with long intervals and to study brain connections in precious specimens.

Animals↗
PubMed1990

Neurons in the sacral parasympathetic nucleus that project to the hypothalamus do not also project through the pelvic nerve--a double labeling study combining Fluoro-gold and cholera toxin B in the rat.

We recently reported that neurons in the sacral parasympathetic nucleus (SPN) project directly to the hypothalamus. In the present study, we examined the possibility that individual neurons in SPN send both an axon into the pelvic nerve and an ascending projection to the hypothalamus. We used a new double-labeling technique in which two sensitive retrograde tracers (Fluoro-gold and cholera toxin subunit B immunocytochemically stained with rhodamine-labeled antibodies) were combined. The effectiveness of this combination for singly and doubly labeling neurons was established in experiments in which both tracers were injected into overlapping areas of the tongue or ventrobasal thalamus. These injections doubly labeled large numbers of neurons in the hypoglossal or dorsal column nuclei, respectively. In studies of the projections of neurons in the SPN, injection of one tracer into the hypothalamus and the other into the pelvic nerve and/or pelvic ganglion singly labeled many neurons (more than 3300 in the 7 examined cases). However, no SPN neurons were doubly labeled. These findings indicate that the SPN in the rat consists of at least two distinct groups of cells, parasympathetic preganglionic neurons and neurons that project to the hypothalamus.

Animals↗
PubMed1990

Evidence that Fluoro-Gold can be transported avidly through fibers of passage.

Small iontophoretic injections of the retrograde tracer Fluoro-Gold were restricted to the dorsal columns in the cervical enlargement of 6 rats. Large numbers of neurons were labeled in the lumbosacral dorsal horn in each rat. In the most effective case, more than 1800 neurons were labeled in alternate sections through nine examined segments. Many neurons were also labeled in lumbosacral dorsal root ganglia of all cases. This study, in contrast to previous reports, indicates that Fluoro-Gold can be transported avidly by axons passing through, but not terminating in, injection sites.

Animals↗
PubMed1990

Habenulopetal catecholaminergic projections in the rat brain: a combined Fluoro-Gold/catecholamine fluorescence study.

Habenulopetal catecholamine (CA)-containing neurons were determined using Fluoro-Gold retrograde tracing combined with a CA-fluorescence technique. A robust number of habenulopetal CA neurons were found mainly in the ipsilateral locus coeruleus (LC), while a considerable number of habenulopetal non-CA neurons were found in the LC, subcoeruleus, A5, A4 and A7 areas.

Animals↗
PubMed1990

Afferent connections of the thalamic paraventricular and parataenial nuclei in the rat--a retrograde tracing study with iontophoretic application of Fluoro-Gold.

The origin of the afferents of the thalamic anterior paraventricular and parataenial nuclei (PVA-PT) in the rat was studied with fluorescent retrograde tracing method. After iontophoretic application of Fluoro-Gold into PVA-PT, many labeled cells were found in the medial frontal cortex, ventral subiculum, claustrum, septum, ventral pallidum, thalamic reticular nuc., zona incerta, hypothalamus, central gray, dorsal raphe nuc., parabrachial nuc., and the laterodorsal tegmental nuc. A few cells were labeled in the medial amygdaloid nuc., amygdalohippocampal area, median raphe nuc., and the locus coeruleus. Occasional neurons were labeled in the ventral lateral geniculate nuc., pretectal area, and in the solitary nuc. and the lateral reticular nuc. in the medulla.

Animals↗
PubMed1990

Projections of substance P-immunoreactive neurons located in the ventromedial medulla to the A7 noradrenergic nucleus of the rat demonstrated using retrograde tracing combined with immunocytochemistry.

Stimulation of neurons located in the ventromedial medulla (VMM), including the nucleus raphe magnus (RMg), produces antinociception which appears to be mediated in part by activation of spinally-projecting noradrenergic neurons located in the A7 catecholamine nucleus. Although the identity of the VMM neurons that project to the A7 nucleus is not known, there is indirect evidence that these neurons contain substance P. This possibility was examined by injecting the retrograde tracer Fluoro-Gold into the A7 nucleus and determining whether substance P-immunoreactive neurons in the VMM were labeled with Fluoro-Gold. The results of these experiments demonstrated that numerous substance P-immunoreactive cells in the RMg, gigantocellular reticular nucleus pars alpha and the paragigantocellular reticular nucleus were retrogradely labeled by an injection of Fluoro-Gold into the A7 nucleus. These observations indicate that substance P-containing neurons in these areas of the VMM project to the A7 nucleus. Thus, the antinociception induced by stimulation of the VMM may be mediated by activation of substance P-containing neurons that project to and activate spinally projecting noradrenergic neurons in the A7 nucleus.

Animals↗
PubMed1991

Distribution and origin of noradrenergic and serotonergic fibers in the cochlear nucleus and inferior colliculus of the rat.

We examined the monoaminergic innervation of the rat cochlear nucleus (CN) and the inferior colliculus (IC) by using retrograde transport of the fluorescent dye Fluoro-Gold combined with immunohistochemistry. We used antisera against the catecholamine synthesizing enzymes tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT), and one against the transmitter serotonin (5-HT). Each substance revealed a distinct pattern of immunoreactive staining in the CN and the IC. In the CN, DBH-immunoreactive (-ir) fibers were present in all subnuclei. The molecular layer of the dorsal CN and the granular layer of the ventral CN, however, were largely devoid of DBH-ir fibers. In contrast, 5-HT-ir fibers were abundant in the molecular layer and the granular cell layer of the CN. In the dorsal CN and the postero- and anteroventral CN, however, this innervation was less dense and evenly distributed across subnuclei. In the IC, the DBH-ir fibers were slightly more numerous in layer 2 of the dorsal cortex than in other subnuclei, while the layer 1 of both the dorsal and the external cortex contained only a few fibers. In contrast, the 5-HT-ir fibers formed a dense network in both the dorsal and external cortices of the IC, while they were less abundant in the remaining subnuclei. PNMT-ir fibers were not found in any of the auditory brainstem nuclei. Following Fluoro-Gold injections into the CN or IC, retrogradely labeled DBH-ir neurons were found in the A6 noradrenergic cell group (locus coeruleus). The CN received additional projections from the A5 noradrenergic cell group, as well as sparse projections from the A4 and A7 cell groups. The serotonergic innervation of the CN and IC originated largely in the B7 serotonergic cell group (dorsal raphe nucleus). Serotonergic neurons in other groups of the raphe nuclei were only occasionally labeled. Our data indicate that both noradrenaline and serotonin may play a role in central auditory processing. Their differential distribution in the IC and CN subnuclei suggests that these transmitter systems might influence different functional circuits.

Animals↗
PubMed1991

The globus pallidus receives a projection from the parafascicular nucleus in the rat.

Study of the afferents of the rat globus pallidus (GP) with Fluoro-gold, a retrograde tracer, revealed retrogradely labeled neurons in the ipsilateral parafascicular nucleus of the thalamus (PF), a previously undescribed afferent of the rat GP. We used the anterograde tracer, Phaseolus vulgaris-leucoagglutinin (PHA-L), to confirm and extend our findings. After injections of PHA-L in the PF, labeled fibers with varicosities and terminal specializations were observed in the ipsilateral GP. The topographical organization of the projection is such that lateral and ventral PF neurons project preferentially to respective parts of the GP, and medial PF neurons project primarily to the ventral GP. There were very few labeled fibers seen in the dorsal or medial GP. The presently described projection from the PF to the GP provides an additional route for the PF to influence basal ganglia circuitry.

Animals↗
PubMed1991

Fluoro-Gold: composition, and mechanism of uptake.

Determining the mechanism by which fluorescent retrograde neuronal tracers are taken up requires knowledge of their composition. It has been claimed that Fluoro-Gold, a retrogradely transported fluorescent neuronal tracer, is 2-hydroxy-4,4'-diamidinostilbene (hydroxystilbamidine), an amidine antibiotic. However, this appears questionable, since the fluorescence spectrograms reported for Fluoro-Gold differ markedly from the spectrograms previously reported for purified hydroxystilbamidine. To help clarify the mechanism by which Fluoro-Gold might be taken up, it was decided to examine its composition and determine whether hydroxystilbamidine was its active agent. Fluoro-Gold was found by mass spectrometry to contain a component with a molecular weight of 280 Da (identical to that of hydroxystilbamidine), and fluorescence spectroscopy demonstrated the existence of a substance with a fluorescence spectrum similar to that of purified hydroxystilbamidine. Although a major fluorescent impurity was also observed, chromatographic separation of different fluorescent components of Fluoro-Gold suggested that the fraction resembling hydroxystilbamidine was responsible for its retrograde labeling of cells. It is concluded that hydroxystilbamidine is the active constituent of Fluoro-Gold. Chemically, hydroxystilbamidine is a weak base. In this respect it resembles True blue, DAPI, Granular blue, bis-benzimide, Nuclear yellow, and several other retrogradely transported molecules. It is suggested that these agents cross cell membranes in their uncharged form and are trapped in lysosomes and endosomes by a favorable pH gradient. Thus, the uptake of this type of retrograde tracer may be an example of a well-understood process occurring widely throughout biological systems: the trapping of weak bases in acidic cellular compartments.

Animals↗
PubMed1991

An enkephalinergic mechanism involved in amygdaloid suppression of affective defence behavior elicited from the midbrain periaqueductal gray in the cat.

A series of recent studies in our laboratory have provided evidence that opioid peptides powerfully suppress feline affective defense behavior at the level of the midbrain periaqueductal gray (PAG). In the present study, we tested the hypothesis that the central (CE) nucleus of the amygdala constitutes a significant inhibitory input to the PAG which utilizes enkephalins as its neurotransmitter or neuromodulator. Cannula-electrodes were implanted into the PAG for the elicitation of affective defense behavior as well as for infusion of opioid antagonists. Monopolar stimulating electrodes were also implanted into the central, lateral and medial amygdaloid nuclei from which suppression or facilitation of affective defense behavior could be obtained. Initially, 4 trials of concurrent, subseizure stimulation of the CE or lateral amygdala at very low (100 microA, 60 Hz) currents and PAG resulted in an immediate suppression of this response which displayed a time dependent decline after 30 min. In the next stage of the experiment, naloxone (2.7, 18.9 and 27.5 nM) was microinjected through the cannula-electrode into the PAG affective defense site and the experimental procedures noted above were repeated. Naloxone treatment (at 27.5 and 18.9 nM) blocked the suppressive effects of CE and lateral amygdaloid stimulation in a dose and time dependent manner. Further analysis revealed that this effect is likely mediated via the mu receptor since the suppressive effects of amygdaloid stimulation were blocked by the selective mu antagonist, beta-Funaltrexamine (0.05 and 0.2 nM) but not by the selective delta-antagonist, ICI 174,864 (0.7 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

Affect↗
PubMed1991

Non-dopaminergic projections from the substantia nigra pars lateralis to the inferior colliculus in the rat.

The substantia nigra pars lateralis (SNI) of the rat was found, by the anterograde and retrograde tracing methods, to send projection fibers to the peripheral shell region surrounding the central nucleus of the inferior colliculus (IC), bilaterally with a clear-cut ipsilateral dominance. SNI neurons sending their axons to the IC were distributed throughout the entire rostrocaudal extent of the SNI. None of these SNI neurons showed tyrosine hydroxylase-like immunoreactivity.

Animals↗
PubMed1991

Origin of cuneate projections to the anterior and posterior lobes of the rat cerebellum.

The present study was carried out to analyze the topography of projections from external cuneate nucleus to the anterior and posterior lobes of the cerebellum and to investigate whether projections to the two lobes come from different cuneocerebellar neurons or from branching axons of the same cells. We used retrograde double-labeling techniques to estimate the incidence of cuneocerebellar neurons projecting to both anterior and posterior lobes via axon collaterals. Cells sending their axons to the lobus anterior were about twice the number of those projecting to the posterior lobe. The double-labeled cells were about 1/7 of all labeled neurons and were located mainly in the more lateral half of the nucleus. Therefore, the two lobes of the cerebellum are likely to receive common information from these cells, but different information from the separate populations of cuneocerebellar neurons that project only to one lobe or the other.

Animals↗
PubMed1991

The projection of locus coeruleus neurons to the spinal cord in the rat determined by anterograde tracing combined with immunocytochemistry.

Pontospinal noradrenergic neurons located in the A5, A7 and locus coeruleus/subcoeruleus (LC/SC) nuclei are the major source of the noradrenergic innervation of the spinal cord. However, the specific terminations of spinally-projecting noradrenergic neurons located in these nuclei have not been clearly defined. The purpose of the experiments described in this report was to more precisely define the spinal terminations of neurons located in the LC/SC using the anterograde tracer phaseolus vulgaris-leucoagglutinin in combination with dopamine-beta-hydroxylase (D beta H) immunocytochemistry. In addition, the spinal cord regions in which LC/SC neurons terminate was assessed by measuring the reduction in the density of D beta H-immunoreactive axon terminals in specific spinal cord regions after a unilateral electrolytic lesion that included LC/SC neurons. The results of these experiments indicate that the axons of LC neurons are located primarily in the ipsilateral ventral funiculus and terminate most heavily in the medial part of laminae VII and VIII, the motoneuron pool of lamina IX, and lamina X. LC neurons provide a moderately dense innervation of the ventral part of the dorsal horn, but only a very sparse innervation of the superficial dorsal horn. The SC projects ipsilaterally in the ventrolateral funiculus and terminates diffusely in the intermediate and ventral laminae of the spinal cord.

Animals↗
PubMed1991

Auditory projections from the cochlear nucleus to pontine and mesencephalic reticular nuclei in the rat.

We investigated projections from the cochlear nucleus in the rat using the anterograde tracer Phaseolus vulgaris-leucoagglutinin. We focused on nuclei in the brainstem which are not considered to be part of the classical auditory pathway. In addition to labeling in auditory nuclei, we found presumed terminal fibers in 4 pontine and mesencephalic areas: (1) the pontine nucleus (PN), which receives bilateral projections from the antero- and posteroventral cochlear nuclei; (2) the ventrolateral tegmental nucleus (VLTg), which receives a contralateral projection from the rostral portion of the anteroventral cochlear nucleus; (3) the caudal pontine reticular nucleus (PnC), which receives bilateral input originating predominantly in the dorsal cochlear nucleus; and (4) the lateral paragigantocellular nucleus (LPGi), which receives projections from all subdivisions of the cochlear nuclei. In the VLTg and PnC, anterogradely labeled varicose axons were often found in close apposition to the primary dendrites and somata of large reticular neurons. Injections of the retrograde fluorescent tracer Fluoro-Gold into the VLTg demonstrated that the neurons of origin are mainly located contralaterally in the rostral anteroventral cochlear nucleus and in the cochlear root nucleus. The relevance of these auditory projections for short-latency audio-motor behaviors and acoustically elicited autonomic responses is discussed.

Animals↗
PubMed1991

Morphology and distribution of efferent vagal innervation of rat pancreas as revealed with anterograde transport of Dil.

Vagal efferent innervation of the pancreas was labeled by anterograde transport of Dil injected into the dorsal motor nucleus (dmnX). While over the entire organ only 19 +/- 3 (or 8 +/- 1%) of the 231 +/- 17 interlobular ganglia received Dil-labeled vagal fibers and terminals, the proximal duodenal lobe (or head) was significantly more densely innervated. Laser scanning confocal microscopy revealed further morphological details of the vagal terminals and their target ganglion cells. No vagal fibers or terminals were found in islets and acinar tissue.

Animals↗
PubMed1991

Prodynorphin- and substance P-containing neurons project to the medial preoptic area in the male Syrian hamster brain.

To determine if substance P- or prodynorphin-containing neurons of the medial nucleus of the amygdala and medial bed nucleus of the stria terminalis send projections to the medial preoptic area in the male Syrian hamster, we placed a fluorescent retrograde tract tracer (either Fluoro-gold, or rhodamine- or fluorescein-impregnated latex microspheres) into the medial preoptic area. Five to seven days later, the animals were treated with colchicine, allowed to survive for 48 h and the brains were processed for immunofluorescence histochemistry. Tissue sections were incubated in either rat anti-substance P or rabbit anti-C-peptide (the C-terminal sequence of dynorphin B) antiserum followed by incubation in either fluorescein- or rhodamine-conjugated anti-rabbit or anti-rat antiserum. When the injection site of retrograde tracer was centered within the caudal one-third of the medial preoptic area, labeled cell bodies were observed caudally in the medial part of the bed nucleus of the stria terminalis. Retrogradely labeled cell bodies were also observed in the posterodorsal subdivision of the medial nucleus of the amygdala. Both prodynorphin and substance P immunolabeling were observed in retrogradely labeled neurons in these two areas but fewer of these projection neurons were immunolabeled with substance P antiserum than with C-peptide antiserum. These projections may play a role in the peptidergic modulation of reproductive behavior in this species.

Amygdala↗