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PubMed1995

Expression of glutamate (AMPA type) and gamma-aminobutyric acid (GABA)A receptors in the rat caudal trigeminal spinal nucleus.

The localization of GABAA receptor gamma 1 and gamma 2 subunits and the AMPA-type glutamate receptor subunits GluR1 and GluR2/3 were identified in the caudal trigeminal spinal tract nucleus (TNC) by immunohistochemistry using specific antibodies. The receptor species on the projecting neurons to the thalamus in TNC were also examined. A retrograde tracer, Fluoro-gold (FG), was injected into the thalamus, and the sections were simultaneously labeled with the antibodies. Injection of FG into the ventral posteromedial nucleus of the thalamus resulted in labeling of scattered neurons contralaterally in the TNC. Most of the neurons labeled by retrograde tracing also showed gamma 1- and gamma 2-like immunoreactivity, while many of the neurons containing FG lacked GluR1- and GluR2/3-like immunoreactivity. These findings show that neurons projecting to the thalamus from the TNC receive GABAergic input via GABAA receptors containing gamma 1 and gamma 2 subunits, while many neurons expressing the AMPA-type receptor did not project to the thalamus.

Animals↗
PubMed1995

The neuroprotective effect of high-dose methylprednisolone in rat spinal cord hemisection.

Multiple studies support a neuroprotective effect for high-dose methylprednisolone (MP) in acute blunt spinal cord injury. We know of no study that addresses the role of MP in prophylaxis for surgical trauma to the spinal cord or for the treatment of non-missile penetrating injuries to the spinal cord. We examined the neuroprotective effect of MP as measured by the retrograde transport of the fluorescent tracer Fluoro-Gold in 20 rats undergoing C-2 hemisection. Mean cell counts of retrogradely labeled rubrospinal neurons were determined 1 week post-injury. The group receiving MP had a significantly higher (P < 0.0001) number of labeled cells (x = 594) compared to controls (x = 387). The highly significant increase in mean cell counts in rats receiving steroids suggests less secondary axonal injury in the MP group. These findings are the first report of a neuroprotective effect of MP in rat spinal cord hemisection. We suggest that MP may be beneficial as prophylaxis during planned or incidental surgical trauma to the spinal cord and after non-missile penetrating injuries to the spinal cord.

Animals↗
PubMed1995

Direct nitric oxide-containing innervation from the rat spinal cord to the penis.

Nitric oxide synthase (NOS)-immunoreactive pathways to the rat penis were studied by combining retrograde tracing by Fluorogold with NOS immunohistochemistry. Injection of the tracer into the penile shaft resulted in Fluorogold labelling in a vast number of NOS-immunoreactive neurons in the major pelvic ganglion. In addition, some neurons in the spinal cord intermediolateral column consistently contained Fluorogold label in the upper lumbar levels. Most of these neurons were also NOS-immunoreactive. These findings suggest that the sympathetic preganglionic, NOS-containing neurons project to the penis, and they may participate in nitric oxide-mediated penile erection.

Adrenergic Fibers↗
PubMed1995

Sites of origin of corticotropin-releasing factor-like immunoreactive projection fibers to the paraventricular thalamic nucleus in the rat.

Neurons containing the peptide corticotropin-releasing factor (CRF) are thought to play a pivotal role in orchestrating autonomic and behavioral responses to stress. CRF afferents to the thalamus are almost entirely concentrated in the midline nuclei, especially in the paraventricular thalamic nucleus. In chloral hydrate-anesthetized male Wistar rats, we sought to determine the sites of origin of the CRF projection fibers to the thalamus, employing a combination of retrograde neuronal tracing and immunocytochemistry for CRF. Prethalamic neurons showing CRF immunoreactivity were detected in the continuum formed by the central nucleus of amygdala and the bed nucleus of the stria terminalis. Additional sources of the CRF fibers to the thalamus were also detected in the parabrachial nuclei and ventrolateral medulla.

Animals↗
PubMed1989

Cholinergic projections to the substantia nigra from the pedunculopontine and laterodorsal tegmental nuclei.

The cholinergic innervation of the compact and reticular parts of the substantia nigra in the rat was investigated by use of highly sensitive retrograde and anterograde tract-tracing methods in combination with choline acetyltransferase immunohistochemistry. The fluorescent tracers True Blue, propidium iodide, or fluorogold were infused preferentially into either nigral subnucleus. Cells positive for choline acetyltransferase and retrograde tracer were found in both the pedunculopontine and laterodorsal tegmental nuclei, although considerably more double-labeled somata were observed in the former than in the latter component of the pontomesencephalotegmental cholinergic complex. Approximately 2-3 times more cholinergic cells were labeled in the peduculopontine and laterodorsal tegmental nuclei when tracer injections were centered in the compact nigral subdivision than when infusions of about the same size were confined totally to the reticular part. Infusions of the anterogradely transported tracer Phaseolus vulgaris leucoagglutinin into the pontomesencephalotegmental cholinergic complex resulted in uptake and transport of that label to both nigral subnuclei, and some of the Phaseolus vulgaris leucoagglutinin-accumulating somata and proximal processes also demonstrated choline acetyltransferase-like immunoreactivity. The Phaseolus vulgaris agglutinin-labeled entities in the substantia nigra exhibited terminal-like profiles that were reminiscent of the pattern of nigral choline acetyltransferase-positive puncta demonstrated immunohistochemically by use of nickel ammonium sulfate enhancement of the final reaction product in the avidin-biotin procedure. These observations strongly support the contention that the pontomesencephalotegmental cholinergic complex is the major source of cholinergic projections to both the compact and reticular portions of the rat substantia nigra.

Animals↗
PubMed1989

Spinal lamina I projection neurons in the rat: collateral innervation of parabrachial area and thalamus.

A major ascending nociceptive pathway from spinal lamina I to the mesencephalon has previously been reported in the cat, rat and monkey. In the present paper, we have used single and double retrograde labeling techniques to describe this projection system and its collateralization to the thalamus in the rat. Injections of wheat germ agglutinin-horseradish peroxidase into the pontomesencephalic parabrachial area labeled cell bodies bilaterally in lamina I and deeper laminae of the spinal cord. Bilateral lesions of the dorsolateral funiculi at thoracic levels reduced labeling of lamina I neurons caudal to the lesions. Combined injections of fluorescent retrograde tracers into the lateral thalamus and parabrachial area resulted in double labeling of projection neurons in lamina I, lamina IV VIII and the lateral spinal nucleus of the cervical and lumbar enlargements. Double-labeled neurons were especially abundant in lamina I. Thus, we have demonstrated a major lamina I projection through the dorsolateral funiculi to the parabrachial area with significant collateralization to the thalamus. Moreover, since more than 80% of retrogradely labeled lamina I spinothalamic tract cells had collaterals to the parabrachial area we have indirectly demonstrated the presence of a dorsolateral funicular pathway for lamina I spinothalamic neurons in the rat. More lamina I neurons were retrogradely labeled from midbrain injections as compared to thalamic injections. The significance of these findings rest on previous work in this and other laboratories and concerns the understanding of spinal nociceptive mechanisms. Lamina I projection neurons are primarily nociceptive-specific in their response properties and have been shown to project to both the midbrain and thalamus via the dorsolateral funiculus in a number of species. The role of this projection system in nociceptive transmission may lie in its ability to distribute precise information to multiple brain stem sites which in turn activate autonomic or affective responses or descending pain modulatory mechanisms.

Animals↗
PubMed1989

Connectivity of striatal grafts implanted into the ibotenic acid-lesioned striatum--II. Cortical afferents.

Grafts of fetal striatal tissue, implanted into the ibotenic acid-lesioned caudate-putamen in adult recipient rats, have previously been shown to receive extensive afferent inputs from various subcortical areas in the host. In the present study, the formation of graft afferents from the host neocortex has been analysed, 3-12 months after transplantation, by means of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin, iontophoretically injected at multiple sites into the host frontal cortex, in combination with intra-transplant injections of the fluorescent retrograde tracer, Fluoro-Gold. From the cortical injection sites, fibres labelled with Phaseolus vulgaris leucoagglutinin could be traced through the corpus callosum, along the myelinated fascicles of the internal capsule, into the host caudate-putamen. The labelled axons passed in large numbers across the host-graft border zone to form a rich terminal plexus that covered large parts of the grafted tissue, in close association with the grafted neurons. The labelled corticostriatal terminal network was dense, particularly in the peripheral portions of the grafts, although it did not reach the density seen in the spared portions of the host caudate-putamen. Injections of Fluoro-Gold into the depth of the striatal grafts labelled large numbers of neurons in the frontoparietal cortical regions. Consistent with previous findings, labelled neurons were also found, ipsilateral to the graft, in the intralaminar nuclear complex of the thalamus, basolateral amygdala, substantia nigra and dorsal raphe. The host neocortical neurons labelled by Fluoro-Gold injections into the graft had the same laminar and regional distribution as the neurons labelled from the homotopic area of the intact striatum, indicating that the cortical afferents to the graft were derived from those corticostriatal neurons which projected to the area of the ibotenic acid-lesioned caudate-putamen into which the graft had been placed. The number of Fluoro-Gold-labelled cortical neurons ipsilateral to the graft reached in the best cases about 1/3 of the number labelled by identical Fluoro-Gold injections into the intact caudate-putamen. Labelled neurons occurred, with a similar distribution, also in the contralateral frontoparietal cortex, but they were considerably fewer in number. The results demonstrate that fetal striatal tissue, implanted into the previously neuron-depleted adult caudate-putamen, receives innervations from all normal principal cortical and subcortical striatal afferent systems, thus pointing to a remarkable capacity of the implanted fetal striatal neurons to become anatomically integrated into the lesioned host striatal circuitry.

Animals↗
PubMed1989

Connectivity of striatal grafts implanted into the ibotenic acid-lesioned striatum--III. Efferent projecting graft neurons and their relation to host afferents within the grafts.

Efferent projections of intrastriatally implanted striatal neurons have been studied using a combination of anterograde and retrograde axonal tracers. Adult rats subjected to a unilateral ibotenic acid lesion of the head of the caudate putamen received cell suspension grafts obtained from 14 15-day-old striatal primordia. Three and a half to 20 months after transplantation the rats received either intratransplant injections of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin or injections of fluorescent retrograde tracers. Fluoro-Gold and rhodamine-labelled latex beads, into the host globus pallidus and substantia nigra. Injections of Phaseolus vulgaris leucoagglutinin located entirely within the grafts labelled axons that ramified extensively within the tissue itself, as well as axons that extended caudally, across the graft host border, along the myelinated fascicles of the internal capsule to arborize in the medial parts of the host globus pallidus. A few axons also reached the entopeduncular nucleus. Injections of Fluoro-Gold into the host globus pallidus labelled large numbers of graft neurons, which had a prominent patchy distribution and were most abundant in the caudal portions of the grafts. Clear retrograde labelling was also seen after injection of Fluoro-Gold or rhodamine beads into the host substantia nigra, although the number of labelled graft neurons was 30-50 times lower than that seen after pallidal injections. Combined injections of Fluoro-Gold into the pallidus and rhodamine beads into the nigra showed that the vast majority of cells labelled from the nigra were also labelled by Fluoro-Gold from the pallidus. In some of the grafted and Fluoro-Gold-injected animals, the fetal donor tissue had been labelled with [3H]thymidine prior to transplantation. Many examples of neurons labelled with both [3H]thymidine and Fluoro-Gold were found after tracer injections into the host globus pallidus, and double-labelled neurons were identified also after Fluoro-Gold injections into the host substantia nigra. In several animals retrograde tracing was combined with labelling of host dopaminergic afferents (by tyrosine hydroxylase immunohistochemistry) and cortical afferents (by injections of Phaseolus vulgaris leucoagglutinin into the host frontal cortex). Comparison of adjacent sections revealed a striking overlap between the patches of Fluoro-Gold-labelled graft neurons (labelled from the host pallidum) and the dense patches of tyrosine hydroxylase-positive terminals. In addition, many of the Fluoro-Gold-labelled cell patches received a high density of cortical afferents labelled by Phaseolus vulgaris leucoagglutinin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Magnocellular tuberomammillary nucleus input to the supraoptic nucleus in the rat: anatomical and in vitro electrophysiological investigations.

Anatomical and electrophysiological methods were used to investigate the existence and role of inputs from the magnocellular tuberomammillary nucleus to the supraoptic nucleus. After injecting either Fluoro-Gold or rhodamine-labeled latex microspheres into the supraoptic nucleus, consistent patterns of retrogradely labeled neurons within the tuberomammillary nucleus were observed. The results indicate that both subdivisions of the supraoptic nucleus, the tuberal and the anterior, receive input from the tuberomammillary nucleus. Injections into the tuberal supraoptic nucleus tended to label more cells in the contralateral tuberomammillary nucleus, while injections into the anterior supraoptic nucleus may label more cells on the ipsilateral side. The in vitro intracellular electrophysiological results support the anatomical findings and extend them in several ways. Some tuberomammillary neurons were found to project to the supraoptic nuclei on both sides of the brain. Intracellular Lucifer Yellow injections into tuberomammillary cells after electrophysiological recording revealed labeled axons that were traceable into the supraoptic nucleus, where apparent varicosities (possible en passant terminals) were seen. Magnocellular tuberomammillary nucleus neurons had characteristic passive and active membrane properties and morphology, similar to histaminergic neurons in this area studied by other workers. Finally, in two of the 21 cases, Lucifer Yellow injection into one neuron revealed dye-coupled pairs of tuberomammillary neurons. Previous work by others has shown that histamine excited cells in the tuberal subdivision of the supraoptic nucleus, stimulating vasopressin release, and that the tuberomammillary nucleus provides histaminergic input to the anterior portion of the supraoptic. The present findings show that the tuberomammillary nucleus supplies input to both subdivisions of the supraoptic nucleus and that this input is provided bilaterally. Taken together with previous work, these data suggest that the tuberomammillary nucleus provides histaminergic input to the supraoptic nucleus and may be involved specifically with vasopressin release.

Action Potentials↗
PubMed1990

Distribution of glutamate decarboxylase-containing neurons in rabbit medulla oblongata with attention to intramedullary and spinal projections.

Functional studies in the rabbit suggest that GABA is an important inhibitory neurotransmitter in the control of cardiovascular, respiratory and neuroendocrine functions by the medulla oblongata. The present work was undertaken to provide a description of the distribution in the rabbit medulla of neurons containing glutamate decarboxylase, an enzyme present in GABA-synthesizing neurons. Combined retrograde axonal transport and immunohistochemical studies were carried out to determine intramedullary and spinal projections of immunopositive neurons located in regions particularly relevant to the interpretation of functional studies. Neurons containing glutamate decarboxylase, putatively GABA-containing neurons, were found in all nuclei of the rabbit medulla with the exception of somatic cranial nerve nuclei and the lateral reticular nucleus. The immunopositive cells were distributed throughout individual nuclei and their morphological appearance was similar to that of neighbouring immunonegative neurons in the nucleus. An exception was encountered in the dorsal motor nucleus of the vagus where the glutamate decarboxylase-containing neurons belong to a population of small neurons easily distinguished from the larger vagal preganglionic cells. Many immunopositive cells in the raphe nuclei, in the medial reticular formation and in the vestibular nuclei have axonal projections to the spinal cord and presumably represent sources of inhibitory bulbospinal control. Within the medulla there were glutamate decarboxylase-containing neurons in the nucleus tractus solitarius with projections to caudal but not to rostral regions of the ventrolateral medulla. These neurons could provide a GABAergic input to respiratory, cardiovascular and neuroendocrine neurons in the caudal ventrolateral medulla. Immunopositive cells projecting from the caudal to the rostral ventrolateral medulla could form part of the population of inhibitory vasomotor neurons known to be present in the caudal ventrolateral medulla. Some glutamate decarboxylase-containing neurons just medial to the nucleus ambiguous in the rostral medulla, in the region containing the Botzinger group, project to the caudal ventrolateral medulla and could therefore provide an inhibitory input to caudal respiratory cells.

Animals↗
PubMed1990

Access of luteinizing hormone-releasing hormone neurons to the vasculature in the rat.

Luteinizing hormone-releasing hormone is secreted into the hypophysial portal vasculature through which it controls the release of the gonadotropins. The peptide also acts as a neurotransmitter in various loci within the central nervous system. It is not known whether these roles are performed by separate populations of luteinizing hormone-releasing hormone neurons. Some recent tracing experiments suggest that this is the case (Silverman et al., J. Neurosci. 7, 2312, 1987; Jennes and Stumpf, Neuroscience 18, 403, 1986). One aspect of this question was addressed in the current study by intraperitoneal introduction of Fluoro-Gold (a retrograde tracer) into male and female rats under various age and hormonal conditions. Brain sections from the anterior olfactory nuclei to the median eminence were treated for the immunocytochemical demonstration of luteinizing hormone-releasing hormone. In all cases, regardless of the age, sex or hormonal condition of the animal, the Fluoro-Gold tracer was found in more than 90% of the luteinizing hormone-releasing hormone neurons. We conclude that virtually all luteinizing hormone-releasing hormone neurons in the rat secrete outside the blood-brain barrier, including those which project to sites within the central nervous system.

Aging↗
PubMed1991

The hypophysiotropic galanin system of the rat brain.

The external zone of the rat median eminence contains a large amount of galanin-immunoreactive terminals indicating that galanin might function as a hypophysiotropic hormone. The possible sources of these galanin-containing nerve terminals were studied in the male and female rat by means of retrograde labeling in combination with fluorescence immunocytochemistry. Fluoro-Gold was used as retrograde tracer, and it was injected peripherally. Fluoro-Gold does not penetrate the blood-brain barrier, but it is taken up by nerve terminals which project to areas supplied by capillaries that lack the blood-brain barrier. The simultaneous detection of Fluoro-Gold taken up by nerve terminals in the median eminence and the endogenous galanin in thin paraffin sections has revealed that approximately 60% of the hypophysiotropic galanin cells are located in the arcuate nucleus. The remaining portion is located in the parvocellular subdivision of the paraventricular nucleus. Only scattered hypophysiotropic galanin cells are present in the medial preoptic area.

Animals↗
PubMed1991

Neurons with access to the general circulation in the central nervous system of the rat: a retrograde tracing study with fluoro-gold.

Central nervous system neurons which have access to the general circulation were identified by injecting the retrograde tracer Fluoro-Gold peripherally. Fluoro-Gold does not penetrate the blood-brain barrier but is taken up by nerve terminals which project to areas supplied by fenestrated capillaries or to the periphery. Fluoro-Gold-accumulating neurons were present in the following regions or cell groups of the central nervous system: diagonal band of Broca; medial preoptic area; organum vasculosum of the lamina terminalis; subfornical organ; anterior periventricular area; paraventricular nucleus; arcuate nucleus; accessory magnocellular nuclei of the hypothalamus; motor neurons of cranial nerves III-VII, and IX-XII in the brainstem and spinal cord; autonomic ganglionic cells of cranial nerve III (Westphal-Edinger nucleus) in the mesencephalon and the intermediolateral column of the spinal cord; sensory ganglia of the cranial nerve V (mesencephalic trigeminal nucleus); and the C1-C2 and A2 adrenergic cell groups in the medulla. In addition, Fluoro-Gold-accumulating neurons were seen in the sensory ganglia of cranial and spinal nerves. Retrograde labeling with Fluoro-Gold can be combined with immunocytochemistry to identify the chemical messengers within Fluoro-Gold-labeled perikarya. Although a large number of neurons are labeled in the central nervous system with Fluoro-Gold when it is administered peripherally, this technique in combination with immunocytochemistry can be a powerful tool to identify selected neuronal systems in the central nervous system.

Animals↗
PubMed1991

Persistence of fluoro-gold following degeneration of labeled motoneurons is due to phagocytosis by microglia and macrophages.

When the neural tracer Fluoro-Gold is used to retrogradely label a population of axotomized neurons, cellular labeling can persist in the axotomized nucleus even when Nissl staining indicates that the injured neurons have degenerated. In order to determine the identity of the labeled cells that remain, this study combines retrograde transport of Fluoro-Gold with immunocytochemical methods for identification of specific non-neuronal cell types following peripheral axotomy and Fluoro-Gold labeling of motoneurons in the dorsal motor nucleus of the vagus in neonatal and adult rats. Fourteen days following cervical vagotomy in neonatal rats, Nissl staining revealed a virtually complete loss of vagal motoneurons. Fourteen days after cervical vagotomy in adult rats, vagal motoneuronal loss was not yet extensive but chromatolysis had clearly begun. Injection of Fluoro-Gold into the vagus nerve just prior to the vagotomy led to Fluoro-Gold labeling of remaining vagal motoneurons. In addition, many other small, brightly labeled cells were present in the lesioned vagal nuclei of all rats. Immunofluorescent identification of astrocytes with anti-glial fibrillary acidic protein and microglia and macrophages with OX42 (anti-C3bi complement receptor) and ED1 (anti-monocyte/macrophage cytoplasmic antigen) demonstrated that the small, bright Fluoro-Gold-labeled cells were non-neuronal, non-astrocytic phagocytes, including microglia. These results indicate that phagocytic microglia and other macrophages sequester Fluoro-Gold in the axotomized dorsal motor nucleus of the vagus of neonatal and adult rats, leading to persistence of fluorescent cellular labeling following the loss of retrogradely labeled axotomized neurons.

Age Factors↗
PubMed1991

Transneuronal transport of herpes simplex virus from the cervical vagus to brain neurons with axonal inputs to central vagal sensory nuclei in the rat.

The recent introduction of live viruses as intra-axonal tracing agents has raised questions concerning which central neurons are transneuronally labelled after application of the virus to peripheral organs or peripheral nerves. Since the central connections of the vagus nerve have been well described using conventional neuronal tracing agents, we chose to inject Herpes Simplex Virus Type 1 into the cervical vagus of the rat. After survival times of up to 3 days the rat brains were processed immunohistochemically using a polyclonal antiserum against herpes simplex virus. Two days after injection of the virus we observed viral antigen in the area postrema and in the nucleus tractus solitarius and the dorsal motor nucleus of the vagus (dorsal vagal complex), principally ipsilaterally. At this survival time the viral antigen in the dorsal vagal complex was largely confined to glial cells. After 3 days the viral antigen was localized both in glia and in nerve cells within the dorsal vagal complex and in brain regions previously demonstrated, using conventional tracing procedures, to contain neurons with axonal projections to the dorsal vagal complex. This was true for medullary, pontine, midbrain and hypothalamic regions and for telencephalic regions including the amygdala, the bed nucleus of the stria terminalis, and the insular and medial frontal cortices. Many of the nerve cells containing viral antigen were displayed in a Golgi-like manner, with excellent visualization of the dendritic tree. Axonal processes, in contrast, were not visualized. We used co-localization studies to confirm previous findings concerning monoamine neurotransmitter-related antigens present in medullary and pontine neurons projecting to the dorsal vagal complex. After 3 days there were many Herpes Simplex Virus Type 1-containing glial cells along the intra-medullary course of the vagal rootlets. However, no viral antigen was found in brain regions containing neurons whose axons pass through the region of glial cell-labelled rootlets. Glial cells containing viral antigen were particularly numerous in brain regions known to receive an input from neurons in the area postrema and the dorsal vagal complex. Taken together with our observation concerning the early appearance of viral antigen within glial cells in the dorsal vagal complex, this suggests that when the virus reaches the axon terminal portion it is transferred to nearby glial cells and possibly enters central neurons by way of these structures.

Amidines↗
PubMed1991

Evidence that some preganglionic sympathetic neurons in the rat contain vasoactive intestinal peptide- or peptide histidine isoleucine amide-like immunoreactivities.

Physiological studies have established that preganglionic sympathetic nerve fibers innervating the rat superior cervical ganglion release a second transmitter, in addition to acetylcholine. Based on pharmacological and histochemical investigations, possible candidates for this non-cholinergic neurotransmitter include vasoactive intestinal peptide and peptide histidine isoleucine amide. For example, previous immunohistochemical studies have demonstrated that antisera raised against both of these peptides stain neural processes in the rat preganglionic cervical sympathetic trunk and in the superior cervical ganglion. In the present study, it was found that, when the cervical sympathetic trunk was ligated, vasoactive intestinal peptide- and peptide histidine isoleucine amide-like immunoreactivities built up on both sides of the ligature. In addition, examination of the thoracic spinal cord in colchicine-treated animals revealed vasoactive intestinal peptide- and peptide histidine isoleucine amide-like immunoreactivies in neuronal cell bodies in the intermediolateral cell column and in the region of the lateral funiculus adjacent to it. In a second group of animals in which retrograde tracing techniques were used, these two regions of the spinal cord were shown to contain most of the cell bodies of the preganglionic neurons that project to the superior cervical ganglion. Smaller numbers of retrogradely labeled neurons were found dorsal to the central canal and in the nucleus intercalatus. When either vasoactive intestinal peptide- or peptide histidine isoleucine amide-like immunostaining and retrograde labeling were examined in the same animals, double-labeled neurons were found in the intermediolateral cell column and in the lateral funiculus. These data demonstrate that vasoactive intestinal peptide- and peptide histidine amide-like immunoreactivities are present in certain of the preganglionic neurons that project to the superior cervical ganglion, supporting the hypothesis that vasoactive intestinal peptide and peptide histidine isoleucine amide are released in the ganglion when these preganglionic neurons are activated.

Animals↗
PubMed1991

Spinal neurons in the zebrafish labeled with fluoro-gold and wheat-germ agglutinin.

This study concerns the identification and location of interneurons in the spinal cord of the zebrafish by way of retrograde tracing from the body musculature. To distinguish motoneurons from interneurons; two tracers were applied: the fluorochrome Fluoro-Gold to label motoneurons, and the trans-synaptically transported compound wheat-germ agglutinin to label motoneurons and the associated interneurons that are considered to be premotoneurons. Because the tracer accumulated mainly in cell bodies (not in neurites), premotoneurons labeled directly from motoneurons could not be distinguished from those labeled via interjacent cells. Both tracers were unilaterally injected into the myotomal muscle at the anal level of the animal. The number of labeled cell bodies in the spinal cord was examined 6, 10 and 16 days after injection. Several technique-oriented experiments were performed in order to map all pathways along with the tracers were incorporated in the neurons. The following observations were made. (1) All Fluoro-Gold-positive cells contained wheat-germ agglutinin, but yet more cells contained only wheat-germ agglutinin; the number of wheat-germ agglutinin-labeled cells was about tenfold higher than the number of Fluoro-Gold-labeled cells. (2) Fluoro-Gold labeling was restricted to cells within one to two spinal cord segments corresponding to the injection site, whereas wheat-germ agglutinin labeling was more diffuse. (3) The position and size of Fluoro-Gold-labeled cells corresponded to those of motoneurons described in previous horse-radish peroxidase experiments. (4) Statistical analysis of the group of wheat-germ agglutinin-labeled cells showed two subpopulations, one with a mean cell size and position corresponding to motoneurons and one with a smaller mean cell size, also positioned within the motor column. The smaller cells were considered to be premotoneurons. The ratio motoneuron:premotoneuron was lowest in the ventrolateral area of the motor column.

Animals↗
PubMed1991

Adrenergic innervation of the rat nucleus locus coeruleus arises predominantly from the C1 adrenergic cell group in the rostral medulla.

Focal iontophoretic injections of the retrograde tracer Fluoro-Gold into the locus coeruleus were combined with immunocytochemistry for phenylethanolamine N-methyltransferase, the final enzyme in the synthesis of epinephrine. Retrograde labeling confirmed recent findings that the major afferents to the locus coeruleus are present in the ventrolateral (nucleus paragigantocellularis) and dorsomedial medulla (nucleus prepositus hypoglossi), areas containing the C1 and C3 adrenergic cell groups, respectively. The Fluoro-Gold label revealed morphologic details of locus coeruleus afferent cells. Labeled neurons in the prepositus hypoglossi region were typically round (10 microns diameter) or ellipsoidal and compressed against the ventricle wall (10 x 20 microns), while those in the paragigantocellularis were most often multipolar and ellipsoidal or triangular in shape (10 x 20-20 x 30 microns). Double labeling in the same tissue sections revealed that locus coeruleus afferent neurons are intercalated among phenylethanolamine N-methyltransferase-positive C1 and C3 neurons. Twenty-one per cent of locus coeruleus afferent neurons in paragigantocellularis stained for phenylethanolamine N-methyltransferase while only 4% of locus coeruleus afferents in the prepositus hypoglossi area exhibited phenylethanolamine N-methyltransferase immunoreactivity. In paragigantocellularis, doubly labeled neurons were usually the smaller locus coeruleus afferents, while in the prepositus hypoglossi phenylethanolamine N-methyltransferase labeling was found in all cell types that project to the locus coeruleus. Phenylethanolamine N-methyltransferase-positive fibers from the C1 and C3 cell groups form an adrenergic fiber bundle in the dorsomedial medulla; in the pons, these fibers appear to exit this bundle and innervate the locus coeruleus. Fibers from the neurons of the C3 cell group also appear to ascend on the dorsal surface of the medulla to innervate the locus coeruleus. The phenylethanolamine N-methyltransferase fiber innervation in the locus coeruleus was dense and highly varicose. Phenylethanolamine N-methyltransferase innervation in the dorsal pons was not restricted to the locus coeruleus but was also prominent in neighboring areas such as Barrington's nucleus and the lateral dorsal tegmental nucleus of Gudden.

Afferent Pathways↗