Distribution of tyrosine hydroxylase and neuropeptide Y-like immunoreactive neurons in rabbit medulla oblongata, with attention to colocalization studies, presumptive adrenaline-synthesizing perikarya, and vagal preganglionic cells

A double-label immunohistochemical study of intramural ganglia from the human male urinary bladder neck

Double-label immunocytochemistry was used to investigate the colocalisation of various neuropeptides and the enzymes nitric oxide synthase (NOS) and tyrosine hydroxylase (TH) in intramural ganglia of the human male urinary bladder neck and trigone. Postmortem specimens were obtained from 7 male infants and children ranging in age from 2 mo to 3 y who had died as a result of cot death or accidental trauma. On average 60% of the intramural neurons were non-TH-immunoreactive (-IR) (i.e. presumptive cholinergic) and 40% were TH- and D beta H-IR (i.e. noradrenergic). Within the non-TH-IR population, calcitonin gene-related peptide (CGRP) was found in 65% of cells, neuropeptide Y (NPY) in 90%, nitric oxide synthase (NOS) in 45%, somatostatin (SOM) in 90%, and vasoactive intestinal polypeptide (VIP) in 40%. The corresponding values for the TH-IR neurons were CGRP (54%), NPY (70%), NOS (58%), SOM (73%) and VIP (40%). All the observed bombesin (BOM)-immunoreactivity was colocalised with TH while 90% of VIP and almost all the CGRP was colocalised with NPY. Less than 5% of neurons were immunoreactive for substance P (SP) or met-enkephalin (m-ENK) and some of these also contained TH. Varicose nerve fibres were seen in close proximity to some of the intramural neurons, the majority of such varicosities showing immunoreactivity to CGRP, VIP or TH. Less common were pericellular varicosities immunoreactive to NPY, SOM or SP. These results demonstrate the neurochemical heterogeneity of intramural neurons in the human bladder neck and provide indirect evidence for the complexity of the peripheral innervation of the human urinary bladder.

Colocalization of somatostatin, neuropeptide Y, neuronal nitric oxide synthase and NADPH-diaphorase in striatal interneurons in rats

The neuropeptides somatostatin (SS), neuropeptide Y (NPY), the enzyme neuronal nitric oxide synthase (nNOS) and enzymatic activity for NADPH diaphorase (NADPHd) are extensively colocalized in striatal interneurons, which has led to the widespread tendency to operationally treat all four substances as being completely colocalized within a single class of striatal interneurons. We have explored the validity of this assumption in rat striatum using multiple-labeling methods. Conventional epi-illumination fluorescence microscopy was used to examine tissue triple labeled for SS, NPY and nNOS, or double-labeled for SS and nNOS or for SS and NPY. In tissue double-labeled for SS and nNOs, confocal laser scanning microscopy (CLSM) images of SS and nNOS labeling were compared to subsequent NADPHd labeling. We found that SS, NPY and nNOS co-occurred extensively, but a moderately abundant population of neurons containing SS and nNOS but not NPY was also observed, as were small populations of SS only and nNOS only neurons. About 80% of SS+ neurons contained NPY, and no NPY neurons were devoid of SS or nNOS. All neurons containing nNOS in rat striatum were found to contain NADPHd. Combining our various quantitative observations, we found that of those striatal neurons containing any combination of SS, NPY, nNOS and NADPHd in rats, about 73% contained all four, 16% contained SS, nNOS and NADPHd, 5% contained SS only, and 6% contained only nNOS and NADPHd. These results indicate that while there is a large population of striatal neurons in which SS, NPY, nNOS and NADPHd are colocalized in rats, there may be smaller populations of striatal neurons devoid of NPY in which SS or nNOS/NADPHd are found individually or together.

The dorsal vagal complex of the ferret: anatomical and immunohistochemical studies

To further the understanding of gastrointestinal function in this species, and in particular to advance our own work concerning central emetic pathways, the cytoarchitecture and the distribution of eight neurochemicals were studied in the ferret dorsal vagal complex (DVC; area postrema, nucleus of the solitary tract [nTS] and dorsal motor nucleus of the vagus). The cytoarchitectural features of this region in the ferret were similar to those seen in other species; however, the ferret possesses a particularly large and distinct subnucleus gelatinosus of the nTS. Dense calcitonin gene-related peptide-immunoreactivity was found in the gelatinous, interstitial and commissural subnuclei of the nTS, with lesser amounts in other regions of the DVC. Enkephalin-immunoreactivity of varying densities was found throughout the DVC. Moderate to dense galanin-immunoreactivity was observed throughout the DVC, with the exception of the subnucleus gelatinosus of the nTS, from which it was virtually absent. Dense neuropeptide Y-immunoreactivity was observed in the subnucleus gelatinosus and interstitial subnucleus, with moderate staining in other regions of the DVC. Neurotensin immunoreactivity was very sparse or absent. Immunoreactivity for serotonin was sparsely distributed throughout the DVC. Moderate somatostatin-immunoreactivity was observed over a large portion of the DVC, but was virtually absent from the gelatinosus and interstitial subnuclei. Substance P immunoreactivity was observed throughout the DVC and was particularly dense in the dorsal/dorsolateral subnucleus and the dorsal aspects of the medial and commissural subnuclei. In terms of its cytoarchitecture the DVC of the ferret is more similar to the cat than the rat, especially with regard to the area postrema and the subnucleus gelatinosus of the nTS. The distribution of neuroactive substances was largely similar to other species; however, differences were present particularly in patterns of immunoreactivity for enkephalin, serotonin, neuropeptide Y and somatostatin.

Müller cells in the retina of the cane toad, Bufo marinus, express neuropeptide Y-like immunoreactivity

We have used light- and electron-microscopic immunohistochemistry to identify the presence of immunoreactivity to neuropeptide Y (NPY) within Müller cells in the retina of the cane toad, Bufo marinus. Müller cells containing NPY-like immunoreactivity (NPY-LI) were identified at the light-microscopic level by the coexistence with immunoreactivity to glial fibrillary acidic protein (GFAP) and at the ultrastructural level by their characteristic relationship to neuron cell bodies and processes. At the light-microscopic level, those cells which contained both NPY-LI and GFAP-LI usually had small cell bodies in the inner nuclear layer, while those cells which contained only NPY-LI were identified as large and small amacrine cells. The radially oriented primary processes in the inner plexiform layer and the vitreal end feet of GFAP-LI Müller cells also expressed NPY-LI. At the ultrastructural level, thin lamellar processes of Müller cells with NPY-LI enclosed some amacrine cell bodies in the inner nuclear layer and amacrine cell dendrites in the inner plexiform layer. These observations suggest that NPY-LI is localized in Müller cells in addition to two types of amacrine cells previously identified in the Bufo retina. This study provides the first evidence that glial elements in the vertebrate retina express NPY-LI.

Medullary neurons activated by angiotensin II in the conscious rabbit

Previous studies have shown that angiotensin II (Ang II) can activate cardiovascular neurons within the medulla oblongata via an action on specific receptors. The purpose of this study was to determine the distribution of neurons within the medulla activated by infusion of Ang II into the fourth ventricle of conscious rabbits, using the expression of Fos, the protein product of the immediate early gene c-fos as a marker of neuronal activation. Experiments were done in both intact and barodenervated animals. In comparison with a control group infused with Ringer's solution alone, in both intact and barodenervated animals, fourth ventricular infusion of Ang II (4 to 8 pmol/min) induced a significant increase in the number of Fos-positive neurons in the nucleus of the solitary tract and in the rostral, intermediate, and caudal parts of the ventrolateral medulla. Double-labeling for Fos and tyrosine hydroxylase immunoreactivity showed that 50% to 75% of Fos-positive cells in the rostral, intermediate, and caudal ventrolateral medulla and 30% to 40% of Fos-positive cells in the nucleus of the solitary tract were also positive for tyrosine hydroxylase in both intact and barodenervated animals. The distribution of Fos-positive neurons corresponded very closely to the location of Ang II receptor binding sites as previously determined in the rabbit. The results indicate that medullary neurons activated by Ang II are located in discrete regions within the nucleus of the solitary tract and ventrolateral medulla and include, in all of these regions, both catecholamine and noncatecholamine neurons.

Peptidergic transmission: from morphological correlates to functional implications

Like non-peptidergic transmitters, neuropeptides and their receptors display a wide distribution in specific cell types of the nervous system. The peptides are synthesized, typically as part of a larger precursor molecule, on the rough endoplasmic reticulum in the cell body. In the trans-Golgi network, they are sorted to the regulated secretory pathway, packaged into so-called large dense-core vesicles, and concentrated. Large dense-core vesicles are preferentially located at sites distant from active zones of synapses. Exocytosis may occur not only at synaptic specializations in axonal terminals but frequently also at nonsynaptic release sites throughout the neuron. Large dense-core vesicles are distinguished from small, clear synaptic vesicles, which contain "classical' transmitters, by their morphological appearance and, partially, their biochemical composition, the mode of stimulation required for release, the type of calcium channels involved in the exocytotic process, and the time course of recovery after stimulation. The frequently observed "diffuse' release of neuropeptides and their occurrence also in areas distant to release sites is paralleled by the existence of pronounced peptide-peptide receptor mismatches found at the light microscopic and ultrastructural level. Coexistence of neuropeptides with other peptidergic and non-peptidergic substances within the same neuron or even within the same vesicle has been established for numerous neuronal systems. In addition to exerting excitatory and inhibitory transmitter-like effects and modulating the release of other neuroactive substances in the nervous system, several neuropeptides are involved in the regulation of neuronal development.

Neuropeptides and neurotransmitter-synthesizing enzymes in intrinsic neurons of the human urinary bladder

The expression of neuropeptides, and the enzymes nitric oxide synthase and tyrosine hydroxylase were examined in intramural ganglia of human urinary bladder using single label immunocytochemistry. Scattered ganglia composed of between 1-36 neurons (median 4) were observed in all layers of the lateral wall of the bladder. These contained immunoreactivity to vasoactive intestinal peptide, nitric oxide synthase, neuropeptide Y, and galanin. Neurons within the bladder were heterogeneous with regard to their content of these antigens, with the proportion of immunopositive cells ranging from 58-84%. Occasional neurons with immunoreactivity to the catecholamine-synthesizing enzyme, tyrosine hydroxylase, were also observed. No cell somata, however, were immunoreactive for enkephalin, substance P, calcitonin gene-related peptide or somatostatin. Varicose terminals entering the ganglia were seen to form pericellular baskets surrounding some of the principal ganglion cells. The most prominent pericellular varicosities were those containing calcitonin gene-related peptide- or vasoactive intestinal peptide-immunoreactivity, followed by those with immunoreactivity for enkephalin, neuropeptide Y, or galanin. Less common were pericellular varicosities with substance P-immunoreactivity, which may represent collateral processes of unmyelinated primary sensory fibres, and presumptive noradrenergic processes containing tyrosine hydroxylase. Some calcitonin gene-related peptide-immunoreactive varicosities constituted a distinct type, terminating as large pericellular boutons 2-4 microns in diameter. Fibres containing nitric oxide synthase- or somatostatin-immunoreactivity were not associated with the intramural neurons. The results demonstrate that intrinsic neurons within the human urinary bladder express a number of neuroactive chemicals, and could in principle form circuits with the potential to support integrative activity.

Changes in enkephalin and neuropeptide Y-like immunoreactivity in rabbit chromaffin tissues during perinatal development

Enkephalin-like immunoreactivity (ENK-LI), neuropeptide Y (NPY)-LI and dopamine-beta-hydroxylase (DBH)-LI were found within the chromaffin cells of both the paraaortic body and the adrenal medulla of the newborn rabbit using immunohistochemistry. Cells positive to DBH-LI were abundant in both the paraaortic body and the adrenal medulla. ENK-LI positive cells were frequent in the paraaortic body, but more sparse in the adrenal medulla. A few cells staining for NPY-LI could be detected in both organs. Some nerve fibers within these organs also contained substance P-LI and calcitonin-gene related peptide-LI. The tissue contents of ENK-LI and NPY-LI, as measured by radioimmunoassay, increased after birth in the adrenal glands and were significantly higher than the fetal levels from 1 week of age. In the paraaortic body the lowest content of ENK-LI was found around birth, whereas the content of NPY-LI was highest at that time. With advancing postnatal age, the content of ENK-LI increased, whereas the content of NPY-LI decreased. At each age, there was a higher content of ENK-LI as compared to NPY-LI in both organs. This indicates that the synthesis of ENK-LI and NPY-LI in the paraaortic body is differently regulated during perinatal development.

Human intermediate reticular zone: a cyto- and chemoarchitectonic study

The primary aim of this study was to provide a comprehensive account of the morphology, topography, and frequency of tyrosine hydroxylase- and substance P-like (TH-LI, SP-LI) immunoreactive neurons of the human intermediate reticular zone (IRt), the putative autonomic zone of the medullary reticular formation. A further aim is to examine the IRt from a three-dimensional perspective using computer reconstruction techniques and compare its relationship with other structures in the rest of the medullary reticular formation. Six adult human brains were obtained from individuals with no sign of cerebral disease and were perfusion fixed. Free-floating transverse sections were immunostained with monoclonal antibodies against tyrosine hydroxylase and substance P by the avidin-biotin-peroxidase technique. The entire IRt displays TH-LI cell bodies and fibers, and thus it is readily distinguishable from the neighbouring gigantocellular and parvicellular reticular nuclei. In contrast, SP-LI cells are restricted to the external part of the IRt that is found in the open medulla, while SP-LI fibers are more widely distributed. The IRt displays TH-LI neurons which are fusiform, oval, and round in shape. The SP-LI neurons of the IRt are primarily oval and fusiform. In preparations stained for Nissl substance, IRt cells were classified as pigmented and nonpigmented. A characteristic feature of the IRt is that its cells are larger (20 +/- 4 micrograms) than those of the laterally adjoining parvicellular (12 +/- 2 micrograms) and clearly smaller than those of the medially adjoining gigantocellular nuclei (33 +/- 6 micrograms). The shape of the IRt is in keeping with the radial organization of the medulla with zones emanating from the fourth ventricle. Three-dimensional computer reconstructions of the cell plots show that 1) TH-LI neurons extend through the entire IRt and densely packed in the rostral part of the ventrolateral IRt and 2) SP-LI neurons are found only in the rostral half of the medulla oblongata.

Calretinin-containing preganglionic nerve terminals in the rat superior cervical ganglion surround neurons projecting to the submandibular salivary gland

The distribution and targets of calretinin-immunoreactive preganglionic nerve terminals in the superior cervical ganglion of the rat were examined using immunohistochemistry and retrograde neuronal tracing. Calretinin-immunoreactive nerve terminals were found throughout the ganglion, forming distinct pericellular baskets around a sub-population of postganglionic neurons. The targets of postganglionic neurons surrounded by calretinin-immunoreactive nerve terminals were determined after injection of tracer into the submandibular salivary gland, the extra-orbital lacrimal gland, the thyroid gland, the anterior chamber of the eye or the skin of the forehead. Only when tracer was injected into the submandibular gland were neurons labelled that were surrounded by calretinin-immunoreactive nerve terminals. When immunohistochemistry using antisera to neuropeptide Y was combined with retrograde tracing, only submandibular gland projecting neurons lacking neuropeptide Y were surrounded by calretinin-immunoreactive terminals. When retrograde neuronal tracer was injected into the superior cervical ganglion, a proportion of retrogradely-labelled neurons in the upper thoracic spinal cord showed relatively weak calretinin-immunoreactivity. All calretinin-immunoreactive terminals in the superior cervical ganglion disappeared following section of the sympathetic chain distal to the superior cervical ganglion. Thus, calretinin is present in a population of preganglionic neurons projecting exclusively to neuropeptide Y non-immunoreactive (presumably secretomotor) neurons innervating the submandibular salivary gland of the rat.

Clonidine and rilmenidine suppress hypotension-induced Fos expression in the lower brainstem of the conscious rabbit

Our current knowledge of the sites of action of the centrally-acting antihypertensive drug clonidine is based almost entirely on experiments in anesthetized animals. The aim of this study was to determine, in conscious rabbits, the sites of action in the brainstem of systemically administered clonidine, as well as its oxazoline analog rilmenidine. Three groups of experiments were carried out. In the first group, hypotension was produced by continuous intravenous infusion of sodium nitroprusside, at a rate sufficient to decrease arterial pressure by 20-30 mmHg, maintained for a period of 60 min. In the second and third groups of experiments, sustained hypotension was also produced by nitroprusside infusion as in the first group, but this was preceded by intravenous injection of clonidine (7-30 micrograms/kg i.v.) or rilmenidine (150-300 micrograms/kg i.v.), respectively. In confirmation of our previous study [Li Y.-W. and Dampney R. A. L. (1994) Neuroscience 61, 613-634], hypotension produced by nitroprusside alone induced a large increase (compared to sham control experiments) in the neuronal expression of Fos (a marker of neuronal activation) in the nucleus of the solitary tract, area postrema, the rostral, intermediate and caudal parts of the ventrolateral medulla, A5 area, locus coeruleus and subcoeruleus, and parabrachial nucleus. In comparison with this group, in rabbits pretreated with clonidine the numbers of Fos-positive cells were greatly reduced (by 76-94%) in the rostral, intermediate and caudal parts of the ventrolateral medulla, area postrema, A5 area, locus coeruleus and subcoeruleus. Clonidine pretreatment also caused a more moderate reduction (by 45%) in the number of Fos-positive cells in the nucleus of the solitary tract, but had no effect on Fos expression in the parabrachial nucleus. Double-labeling for tyrosine hydroxylase and Fos immunoreactivity showed that clonidine pretreatment greatly reduced the numbers of both catecholamine and non-catecholamine Fos-positive neurons. Rilmenidine pretreatment also greatly reduced Fos expression in the lower brainstem, with a very similar pattern to that observed after clonidine pretreatment. The results indicate that in conscious animals both clonidine and rilmenidine cause a widespread but selective inhibition of neurons in the pons and medulla that are normally activated by a hypotensive stimulus. In contrast to previous observations in anesthetized animals, the results suggest that (i) systemic administration of both drugs inhibits non-catecholamine as well as catecholamine neurons in the ventrolateral medulla, and (ii) the regional pattern of neuronal inhibition following administration of equipotent hypotensive doses of both drugs is very similar.

Co-localization of neurotransmitter immunoreactivities in putative nitric oxide synthesizing neurones of the cat brain stem

The distribution of nitric oxide producing neurones in the medulla oblongata of the cat was investigated using nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, and nitric oxide synthase (NOS) immunohistochemistry. The pattern of staining obtained with both methods was found to be similar. Strongly diaphorase and NOS reactive neurones were present in the paramedian and lateral tegmental fields, including the regions occupied by the A1/C1 catecholamine cell groups, the nucleus ambiguus and lateral reticular nucleus, and in a number of sensory nuclei including the nucleus of the tractus solitarius and the dorsal column nuclei. The extent of co-localization of NADPH-diaphorase with a number of neuropeptides and neurotransmitters was investigated by combining NADPH-diaphorase histochemistry with immunocytochemistry for neuropeptide Y, somatostatin, glutamate, cholecystokinin and tyrosine hydroxylase. NADPH-diaphorase reaction product was observed in neurones immunoreactive for glutamate and somatostatin. These double-labelled cells were found in the paramedian region, lateral reticular field, the nucleus prepositus hypoglossi and in the rostral nucleus of the tractus solitarius. In the rostral ventrolateral medulla NADPH-diaphorase/somatostatin immunoreactive cells were found in the paragigantocellular nucleus. NADPH-diaphorase/glutamate immunoreactive cells overlapped the nucleus ambiguus, the lateral reticular nucleus and the A1/C1 catecholaminergic cell groups. In addition, a few NADPH-diaphorase/glutamate immunoreactive cells were found in the paraolivary area and gigantocellular tegmental field, in the external cuneate and infratrigeminal nuclei. The functional implications of the co-localization of nitric oxide with these neurotransmitters in areas of the medulla concerned with cardiovascular regulation is discussed.

Immunolocalization of putative neurotransmitters innervating autonomic regulating neurons (correction of neurones) of cat ventral medulla

This study investigated possible sites of contact of nerve fibers containing a range of putative neurotransmitter substances onto neurons in the cat ventral medulla oblongata concerned with autonomic, particularly cardiovascular, regulation. The parasympathetic preganglionic neurons of the nucleus ambiguous (correction of ambiguus) were identified by retrograde horseradish peroxidase tracing from the vagus nerve, and the groups of neurons in the A1 and C1 cell areas and the raphe nucleus by catecholamine enzyme or 5-hydroxytryptamine (5-HT) immunohistochemistry, respectively. Immunoreactive (-ir)nerve fibers and terminals in the vicinity if these neurons were visualized by subjecting the sections to a dual-staining technique using a brown peroxidase-diaminobenzidine reaction product and a blue alkaline phosphatase-Fast blue reaction product. By employing monochrome photography with combinations of blue and orange-red filters, it was possible to discriminate neural elements displaying one or the other reaction product, or colocalization of reaction products. The results revealed the presence of calcitonin gene-related peptide (CGRP) and galanin (GAL)-ir in some motoneurons of the nucleus ambiguus, but not in those innervating the heart via the cardiac vagus nerve. The latter group of parasympathetic efferent neurons were found to be densely innervated by fibers immunoreactive for dopamine beta-hydroxylase (DBH, indicating noradrenaline), glycine (GLY), gamma-aminobutyric acid (GABA), 5-HT, enkephalin (ENK), neuropeptide Y (NPY), substance P (SP), and thyrotropin-releasing hormone (TRH), and, to a lesser extent, by other neuropeptide-ir fibers. The catecholamine cells of the rostral C1 and caudal A1 groups showed a broadly similar pattern of innervation, most noticeably by fibers immunoreactive for DBH, GABA, 5-HT, cholecystokinin (CCK), CGRP, ENK, GAL, NPY, and SP. The 5-HT-ir neurons of the raphe nucleus, some also containing SP, TRH, ENK, or corticotropin-releasing factor (CRF)-ir, were most prominently innervated by terminals containing DBH, GABA, CCK, ENK, NPY, TRH, somatostatin (SRIF), and vasoactive intestinal polypeptide (VIP)-ir. Although the proof that these groups of neurons receive functional synaptic contacts from the immunoreactive fibers awaits further ultrastructural studies, the results do suggest that a wide range of putative transmitters may influence the activity of efferent neurons in the cat medulla controlling autonomic functions.

Ontogeny of neurotransmitter systems in the paracervical ganglion and uterine cervix of the rat

BACKGROUND

The paracervical ganglia (PG) are components of the pelvic plexus that provides sensory and motor innervation to the reproductive system of the female rat. Several neurotransmitters including norepinephrine (NE), acetylcholine (ACh), neuropeptide Y (NPY), and vasoactive intestinal polypeptide (VIP) are present in neurons of the adult PG and in axons innervating the adult uterus and uterine cervix. The current study was undertaken to describe the onset of immunoreactivity of these neurotransmitters and neuropeptides during development.

METHODS

Female rats, ages E18 to P36, were prepared for immunohistochemistry for TH (tyrosine hydroxylase, a marker of noradrenergic neurons), NPY, or VIP as well as the histochemical demonstration of acetylcholinesterase (AChE).

RESULTS

All four markers were detected in neurons of the PG at E18. Changes in the appearance of these markers from E18 to P36 reflected previously described growth changes in the PG. Axons containing AChE, TH, NPY, or VIP were first detected within the cervix at E20. Immunopositive axons first appeared as thick, unbranched structures at the outermost portion of the cervical myometrium. Over time, these axon bundles ramified to form discrete varicose axons. The ingrowth was similar for axons containing each of the four markers.

CONCLUSIONS

The relative density of each neuronal type in the PG was reflected in the density of axons containing the same marker in the cervix. Changes in neurotransmitter/neuropeptide staining of PG neurons or axons in the cervix were not observed as the animals approached puberty.

Colocalization of nitric oxide synthase with vasoactive intestinal peptide, neuropeptide Y, and tyrosine hydroxylase in nerves supplying the human ureter

The distribution and patterns of colocalization of nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH) were examined in nerve fibers supplying the human lower ureter using double label immunofluorescence. Many nerve fibers immunoreactive for NOS were observed within the ureter. Positive varicose fibers were seen running longitudinally within the smooth muscle bundles, particularly those of the inner layers of the ureter. Immunoreactive axons were also prominent within the subepithelium, and as plexi surrounding many blood vessels. The colocalization studies indicated that NOS was never present in presumptive sympathetic nerve fibers expressing TH. All fibers containing VIP, however, were also immunoreactive for NOS. In addition, a minor population of NOS fibers did not contain VIP. Neuropeptide Y coexisted with NOS in a significant number of nerve terminals, although fibers expressing only NPY were equally common. Several immunochemically distinct nerve populations can therefore be distinguished in the human ureter: (1) nerves containing NOS either with or without VIP; (2) NOS-immunoreactive fibers with NPY; and (3) those fibers expressing TH or NPY which do not contain NOS. The results indicate that some non-noradrenergic peptide-containing nerves in the human ureter have the capacity to synthesize nitric oxide (NO), and that NO may be involved in the regulation of ureteric motility.

Patterns of neuronal colocalisation of tyrosine hydroxylase, neuropeptide Y, vasoactive intestinal polypeptide, calcitonin gene-related peptide and substance P in human ureter

The patterns of colocalisation of neuropeptides, tyrosine hydroxylase (TH), and protein gene product 9.5 (PGP), were studied in nerve fibres supplying the upper and lower human ureter using a double labelling immunofluorescence technique. The majority (85%-95%) of nerve fibres within the ureter contained neuropeptide Y-like immunoreactivity (NPY-LIR), in combination with other peptides. Approximately 52%-63% of the total ureteral innervation was made up of NPY-LIR fibres also expressing TH-LIR, while 21%-42% of fibres contained NPY-LIR in combination with vasoactive intestinal polypeptide (VIP)-LIR. These two immunochemically defined classes did not overlap, since TH- and VIP-LIR were never present within the same nerve fibre. Other minor populations of neurones included those containing calcitonin gene-related peptide (CGRP)-LIR in combination with substance P (SP)-LIR (4%-17%) and those without SP (5%). Rare coexistences were also noted between CGRP- and VIP-LIR (1%-2%), CGRP- and NPY-LIR (< or = 1%), and CGRP- and TH-LIR (< 1%). Regional differences in innervation were found. There were fewer of each class of nerve fibres in the upper ureter compared to the lower ureter. In addition, the proportion of VIP/NPY-LIR fibres of the total innervation was less in the upper ureter, where they were very sparse. Differences in the distribution to various tissue targets were also observed. In the lower ureter, TH/NPY-LIR fibres were localised predominantly to the outer muscle fascicles and adventitia, while VIP/NPY immunoreactive nerves supplied the submucosa and inner smooth muscle fascicles. Both of these populations were also found around blood vessels. A population of presumptive sensory fibres expressing CGRP/SP-LIR were typically present immediately beneath the urinary epithelium and around blood vessels, and only very rarely within muscle fascicles. The finding that TH/NPY- and VIP/NPY-LIR fibres innervate different layers of the ureter raises the possibility that the muscle layers of the ureter may be independently controlled.

Expression of Fos-like protein in brain following sustained hypertension and hypotension in conscious rabbits

The purpose of this study was to examine comprehensively and quantitatively the effects of sustained hypertension and hypotension on neuronal expression of Fos, the protein product of the proto-oncogene c-fos, in the brain of conscious rabbits. Hypertension or hypotension was produced by continuous intravenous infusion of phenylephrine or nitroprusside, at a rate sufficient to increase or decrease, respectively, arterial pressure by 20-30 mmHg, maintained for a period of 60 min. In comparison with a sham control group of rabbits that were infused with the vehicle solution alone, hypertension induced a significant increase in Fos immunoreactivity in the area postrema, the nucleus tractus solitarii, the caudal and intermediate ventrolateral medulla, the lateral parabrachial nucleus and the central nucleus of the amygdala. Double-labelling for tyrosine hydroxylase and Fos immunoreactivity showed that few (approximately 5%) of the Fos-positive neurons in the caudal and intermediate ventrolateral medulla in this group of animals were also positive for tyrosine hydroxylase. Hypotension also produced a significant increase in Fos immunoreactivity in the above regions, as well as in the rostral ventrolateral medulla, the A5 area, the locus coeruleus and subcoeruleus, the paraventricular nucleus, the supraoptic nucleus, the arcuate nucleus and the medial preoptic area. Approximately 65% of neurons in the rostral, intermediate and caudal ventrolateral medulla that expressed Fos following hypotension were also positive for tyrosine hydroxylase. Similarly, in the pons, approximately 75% of Fos-positive cells in the locus coeruleus, subcoeruleus and A5 area were positive for tyrosine hydroxylase. In the hypothalamus, 92% of Fos-positive neurons in the supraoptic nucleus, and 37% of Fos-positive neurons in the paraventricular nucleus, were immunoreactive for vasopressin. Our results demonstrate that hypertension and hypotension induce reproducible and specific patterns of Fos expression in the brainstem and forebrain. The distribution patterns and chemical characteristics of Fos-positive neurons following sustained hypertension or hypotension are significantly different. In particular, hypotension, but not hypertension, caused Fos expression in many tyrosine hydroxylase-positive cells within all pontomedullary catecholamine cell groups.

Light- and electron-microscopic analysis of neuropeptide Y-immunoreactive profiles in the cat spinal dorsal horn

The organization of neuropeptide Y-containing profiles in the dorsal horn of cat lumbosacral spinal cord was examined in an immunocytochemical study employing a specific antiserum against neuropeptide Y. Light-microscopic inspection revealed heavy concentrations of immunoreactive axons and varicosities within the superficial layers of the dorsal horn (laminae I and II) and only low to moderate numbers of positive terminals in the deeper layers (laminae III-VI). Neuropeptide-Y immunoreactivity in the superficial laminae occurred primarily as single punctate terminals, although in sagittal sections long rostrocaudally orientated fibres were also found. Immunoreactive fibres in the deeper layers were usually long and beaded. Two-hundred and eight neuropeptide Y-immunoreactive profiles throughout laminae I-VI were examined through serial sections with the electron microscope, and the overwhelming majority (n = 194) was confirmed to be axon terminals, most of which (95%) formed synaptic junctions. These terminals were packed with small irregularly shaped agranular vesicles, together with a number of large dense-core vesicles. Immunoreactivity was homogeneously scattered throughout the cytoplasm, and was also associated with the dense-core vesicles. A few neuropeptide Y-containing profiles (n = 14) were difficult to classify but they could have been vesicle-containing dendrites. The postsynaptic targets of neuropeptide Y-positive terminals were similar throughout each dorsal horn lamina. Most frequently, neuropeptide Y-positive boutons formed axodendritic and axosomatic synaptic junctions (range = 64% of synapses in laminae V/VI to 83% in lamina III). A smaller proportion of synapses were found upon other axon terminals and in laminae I-III the postsynaptic axon terminals were sometimes the central boutons of glomeruli. A number of terminals, especially those in lamina II, formed multiple synapses which often comprised a triadic arrangement. These findings suggest that neuropeptide Y regulates spinal sensory transmission through both a postsynaptic action upon dorsal horn neurons and a presynaptic action upon primary afferent terminals.

Bulbospinal neuropeptide Y-immunoreactive neurons in the rat: comparison with adrenaline-synthesising neurons

Immunohistochemistry and retrograde tracing using cholera toxin B subunit colloidal gold (CTB-gold) has been used to identify neurons in the medulla that contain neuropeptide Y and project to the area of the intermediolateral cell column in either the upper (T2-T4) or the lower (T8-T9) thoracic spinal cord. The rostrocaudal distributions of neuropeptide Y neurons and neuropeptide Y/CTB-gold neurons have been compared with the distributions of adrenaline-synthesising, phenylethanolamine N-methyltransferase-containing neurons and phenylethanolamine N-methyltransferase/CTB-gold neurons visualised in adjacent sections. In particular areas of the rostral medulla similarities in the numbers and distributions of neuropeptide Y neurons and phenylethanolamine N-methyltransferase neurons suggested a coexistence of the peptide within the catecholamine neurons. However, at the most rostral levels of the rostral ventral medulla, the large numbers of phenylethanolamine N-methyltransferase neurons were not matched by similar numbers of neuropeptide Y neurons, so that the phenylethanolamine N-methyltransferase neurons in this area could not all contain neuropeptide Y. In the rostral ventral medulla fewer neuropeptide Y/CTB-gold neurons than phenylethanolamine N-methyltransferase/CTB-gold neurons were observed, so that these bulbospinal peptide neurons might define a subset of the phenylethanolamine N-methyltransferase/CTB-gold neurons, accounting for 25% of the total phenylethanolamine N-methyltransferase bulbospinal projection from the rostral ventral medulla. Other neuropeptide Y/CTB-gold neurons in the dorsal medulla are also likely to contain phenylethanolamine N-methyltransferase. Finally, a population of neuropeptide Y/CTB-gold neurons was identified in the caudal ventral medulla, these neurons appear not to contain catecholamine synthesising enzymes.

Heterogeneity in calbindin-D28k expression in oxytocin-containing magnocellular neurons of the rat hypothalamus

We have used a double-labeling immunofluorescence method to examine whether oxytocin-containing magnocellular neurons possess a calcium-binding protein, calbindin-D28k, in the hypothalamus of the rat. In the supraoptic nucleus, most oxytocin-immunoreactive cells were also stained for calbindin-D28k. However, in the magnocellular part of the paraventricular nucleus nearly all oxytocin-labeled cells were devoid of calbindin-D28k. In the anterior commissural nucleus, approximately one-third of oxytocin-stained cells were also calbindin-D28k-immunoreactive, but the other cells were negative for calbindin-D28k. This study indicates that there may be distinct chemical features between oxytocin-containing magnocellular neurons of the supraoptic nucleus compared to those of the paraventricular nucleus.

Regional distribution of putative NPY Y1 receptors and neurons expressing Y1 mRNA in forebrain areas of the rat central nervous system

Using monoiodinated radioligands of peptide YY (PYY), and the recently introduced neuropeptide Y (NPY) analogue [Leu31, Pro34]NPY, receptor binding sites of the Y1 and Y2 type were localized in the rat brain by quantitative in vitro autoradiography. The binding specificity and affinity of both radiolabelled ligands were analysed by ligand binding studies employing rat brain membrane homogenates from cerebral cortex and hippocampus. Using in situ hybridization histochemistry, the regional distribution and cellular localization of mRNA encoding the Y1 receptor were investigated in rat brain sections and compared to the distribution of Y1-specific binding sites. PYY binds to both Y1 and Y2 receptors, while long C-terminal fragments such as NPY13-36 and NPY-16-36 bind preferentially to Y2 receptors. [Leu31,Pro34]NPY is a specific agonist for Y1 receptors. Highest densities of [125I]PYY binding sites were found in the cerebral cortex, the thalamus, the lateral septum, the hippocampus and the mesencephalic dopaminergic areas. In order to block putative Y2 receptors, a series of [125I]PYY binding experiments was performed in the presence of NPY13-36 (1 microM), a Y2 preferring C-terminal fragment. High densities of binding sites remained present in the cerebral cortex, the thalamus and the medial mammillary nucleus when NPY13-36 was present in the incubation medium. Furthermore, these areas were highly enriched with [125I][Leu31,Pro34]NPY binding sites. In contrast, the hippocampal complex had its binding capacity reduced by approximately 50%, while the lateral septum and mesencephalic dopaminergic areas had their binding capacities reduced even further. Linear regression analysis showed a high degree of correspondence between [125I][Leu31,Pro34]NPY binding and that obtained with [125I]PYY in the presence of 1 microM NPY13-36, suggesting that the two independent approaches to visualizing Y1 binding sites are comparable. In situ hybridization histochemistry revealed high levels of Y1 mRNA in the granular cell layer of the hippocampal dentate gyrus, several thalamic nuclei and the hypothalamic arcuate nucleus. Moderate levels of Y1 mRNA were seen in the frontoparietal cortex, several thalamic nuclei, the hippocampal pyramidal layers, the subiculum, the olfactory tubercle, the claustrum and a number of hypothalamic nuclei. The mesencephalon, the amygdala and most basal ganglia showed very low levels of hybridization. The present study further clarifies the anatomical distribution of multiple NPY binding sites within the central nervous system of the rat, and extends earlier suggestions that Y1 and Y2 receptor types are present within the central nervous system.

Substance P- and tyrosine hydroxylase-containing neurons in the human dorsal motor nucleus of the vagus nerve

The aim of this study was to provide a comprehensive account of the topography, morphology, and frequencies of the substance P- and tyrosine hydroxylase-containing neurons in the human dorsal motor nucleus of the vagus nerve. The morphology of immunoreactive neurons was studied and the variations of the cell distributions were presented by three-dimensional computer reconstructions. Three types of substance P-like immunoreactive neurons were identified. They were predominantly located in the dorsointermediate, centrointermediate, caudointermediate, and caudal division of the dorsal motor nucleus of the vagus nerve. The morphology of substance P-like immunoreactive neurons varied according to the subnuclei in which they were found. Three types of tyrosine hydroxylase-like immunoreactive neurons were identified, mainly in the periphery of the dorsal motor nucleus of the vagus nerve, including the medial fringe, ventrointermediate, and dorsointermediate subnuclei of the 10. Many cells throughout the ventrointermediate subnucleus of the dorsal motor nucleus of the vagus nerve are seen ventrally to intermingle with the tyrosine hydroxylase neurons of the intermediate reticular zone. Computer reconstructions provided a three-dimensional view of the positions of substance P- and tyrosine hydroxylase-like immunoreactive neurons within the subdivisions of the dorsal motor nucleus of the vagus nerve. The uneven distribution of substance P- and tyrosine hydroxylase-like immunoreactive neurons within the subdivisions suggests an involvement of these substances in some, but not all, autonomic functions of the dorsal motor nucleus of the vagus nerve.

Immunohistochemical study of catecholamine enzymes and neuropeptide Y (NPY) in the rostral ventrolateral medulla and bulbospinal projection

The purpose of this study was to determine whether neuropeptide Y (NPY) terminals in the intermediolateral spinal cord originate from the rostral ventrolateral medulla (RVLM). Immunohistochemical staining of tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), phenylethanolamine-N-methyltransferase (PNMT), and NPY in the rat brainstem and spinal cord were performed in this study in order to examine consequences of lesions of the RVLM and of intracisternal injections of 6-hydroxydopamine (6-OHDA) on catecholamine and NPY immunoreactivity in the intermediolateral column (IML) of rats. In addition, ricin, a retrograde neurotoxin, was applied in the superior cervical ganglion (SCG) to determine its effect on catecholamine and NPY immunoreactivity in the IML. Computer-aided image analysis was used to quantify the immunohistochemical changes in the RVLM and spinal cord. The results demonstrated that many catecholamine- and NPY-containing neurons and/or fibers existed in the RVLM and their terminals were found in the IML. After administration of 6-OHDA intracisternally, the catecholamine and NPY immunoreactivities were decreased both in the brainstem and IML of the spinal cord. Following unilateral microinjection of 6-OHDA into the RVLM, the number of NPY- and catecholamine-containing neurons decreased and there was a reduction in neuron terminals on the ipsilateral side. After injection of ricin into the SCG, the catecholamine and NPY neurons of the medulla were not affected, whereas their terminals in the IML decreased ipsilaterally. These results indicate that most of the catecholamine- and NPY-immunoreactive terminals found in the IML originated in the RVLM. These terminals appear to project towards the superior cervical ganglia.

Innervation of the monotreme gastrointestinal tract: a study of peptide and catecholamine distribution

The distribution of neurons and endocrine cells containing various peptides or catecholamines was examined in the digestive tracts of the echidna (Tachyglossus aculeatus) and the platypus (Ornithorhynchus anatinus). Comparisons were made with published studies in other species in order to obtain a broader view of the phylogenetic distribution and possible functions of gut peptides and catecholamines. Further comparisons between the echidna and platypus were made in light of their different dietary features and gut histology. The distribution of neurons and axons containing catecholamines or various peptides resembled that in other species (such as the frequent appearance of axons containing substance P and vasoactive intestinal peptide in the intestinal mucosa, and axons containing substance P or enkephalins in the circular muscle). In both species, the stomach histologically resembles the esophagus, being aglandular and lined with stratified squamous epithelium. Innervation of these two organs was similar but not identical, with a greater array of peptides found in the gastric muscle. The intestinal mucosa was densely innervated in both species. The platypus small intestine is unusual in having a thick and deeply folded mucosa (but no villi), in which the superficial epithelium is absent or incomplete at many sites; many axons travel close to these luminal surfaces. Many (putative noradrenergic) axons associated with blood vessels contained neuro-peptide Y, but there was no evidence for intrinsic catecholamine-containing neurons. Somatostatin and cholecystokinin were present in some endocrine cells, but unlike many mammals, absent in neuronal tissue. These studies have shown that there are many strong similarities between monotremes and other mammals in the distribution and array of peptides found within nervous and endocrine tissues of the digestive tract. However, numerous small differences of the echidna and platypus innervation may be correlated with their different digestive structures.

Effect of cervical vagotomy on catecholaminergic neurons in the cranial division of the parasympathetic nervous system

This study provides evidence of catecholaminergic neurons in the cranial division of the parasympathetic nervous system. Presumptive catecholaminergic preganglionic neurons in the dorsal motor nucleus of the vagus (DMX) were revealed by a clearcut depletion of intracellular catecholamine-synthesizing enzyme immunoreactivity induced by unilateral cervical vagotomy and identified on tissues immunocytochemically processed for tyrosine hydroxylase (TH), dopamine beta-hydroxylase (D beta H) or phenylethanolamine N-methyltransferase (PNMT). This experimental design was essential because of the recent failure in two species to reproduce data previously obtained in double-label (combined immunocytochemical-retrograde transport) studies. Vagotomy data confirmed three spatially-segregated populations of catecholaminergic visceromotor neurons in the DMX. These cell bodies were morphologically identical to preganglionic neurons observed on alternate tissues stained for Nissl substance or immunostained for choline acetyltransferase (ChAT), the enzyme biosynthesizing acetylcholine. Neurons in the central and medial DMX demonstrated fall-off of TH-like immunoreactivity (LI) ipsilateral to the vagotomy at levels caudal to the obex. This cell group is assumed to be predominantly dopaminergic since relatively few neurons at this level of the DMX expressed D beta H-LI and none were immunostained for PNMT. A second population of immunoreactive neurons, concentrated in the rostral-lateral region of the DMX, was depleted of D beta H-LI on the ipsilateral side but did not express PNMT. These visceromotor neurons may, therefore, biosynthesize noradrenaline and belong to the rostral pole of the A2 area. A third population of presumptive adrenergic vagal dorsomotor neurons in the rostral-medial DMX was depleted of TH-, D beta H- and PNMT-LI at levels of the ipsilateral nucleus anterior to obex. Patterns of depletion of cytoplasmic enzyme-immunoreaction product were identical in all cases irrespective of the site of the transection or the postoperative survival period. Quantitative analysis demonstrated statistically significant loss of immunolabeled neurons in rostral and caudal subgroups of the DMX on the side ipsilateral to the vagotomy. It is concluded that catecholaminergic processes in the vagus nerve, as previously identified by the aldehyde-induced histofluorescence method, may partly arise from the lower brainstem.

Renal sympathetic preganglionic neurons demonstrated by herpes simplex virus transneuronal labelling in the rabbit: close apposition of neuropeptide Y-immunoreactive terminals

Renal sympathetic preganglionic neurons in the spinal cord of rabbits were transneuronally retrogradely labelled by injection of Herpes simplex virus type 1 into the renal nerve and immunohistochemical demonstration of viral antigen. The morphology of the labelled neurons was examined, particularly with respect to the shape and extent of their dendritic trees. Double-labelling immunohistochemical studies were performed to determine the relationship of neuropeptide Y-immunoreactive axons to virus-labelled perikarya and dendrites. The shape of the renal sympathetic preganglionic neurons differed according to whether the neurons were located in the intermediolateral cell column or in other sympathetic areas. The neurons in the intermediolateral cell column had very long dendrites, extending in the rostrocaudal and mediolateral directions. The medially oriented processes extended towards and beyond the central canal. The laterally oriented dendritic processes projected within the dorsolateral funiculus, towards the edge of the spinal cord. Neuropeptide Y-immunoreactive fibres were concentrated in regions containing renal sympathetic preganglionic neurons of the spinal segments examined (T7-L2). Immunoreactive varicose terminals were closely opposed to individual preganglionic neurons, especially to the dendritic processes of these neurons. Our findings indicate that neurotransmitter candidates such as neuropeptide Y are likely to influence renal preganglionic neurons by an input to dendritic processes at some distance from the perikarya. Electrophysiological and other functional studies utilizing applications of neurotransmitter candidates onto these neurons should take this into account.

Distribution of proneuropeptide Y-derived peptides in the brain of Rana esculenta and Xenopus laevis

The distribution of proneuropeptide Y-containing perikarya and nerve fibers in the brain of Rana esculenta and Xenopus laevis was determined with antisera directed toward neuropeptide Y and the carboxyl terminal flanking peptide. The distribution of proneuropeptide Y-like immunoreactivity was similar in both anurans. In the telencephalon, immunoreactive perikarya were found in the olfactory bulb, all subdivisions of the pallium, the septum, pars lateralis of the amygdala, the nucleus accumbens, and the anterior preoptic area. In the diencephalon, labelled perikarya were detected in the ventromedial, ventrolateral and central thalamic nuclei, the magnocellular preoptic nucleus, the suprachiasmatic nucleus, the posterior tuberculum, and the infundibulum. Amacrine-like cells were stained in the retina. In the pretectal area, posterior thalamic neurons showed intense, Golgi-like immunostaining. In the mesencephalon, immunoreactive cells were found in the reticular nucleus, the anteroventral tegmental nucleus, the optic tectum, the interpeduncular nucleus, and the torus semicircularis. In the rhombencephalon, labelled perikarya were detected in the secondary visceral nucleus, the central gray, the nucleus of the solitary tract, the dorsal column nuclei, and the spinal nucleus of the trigeminal nerve. Immunoreactive nerve fibers were observed in all areas of the brain that contained labelled perikarya. The densest accumulations were found in the accessory olfactory bulb, pars lateralis of the amygdala, the ventral habenula, the posterior pituitary, the optic tectum, the interpeduncular nucleus, and the saccular nucleus. The distribution of proneuropeptide Y-like immunoreactivity in the anuran brain showed many similarities to the distribution described for the amniote brain.

Organization of presumptive catecholamine-synthesizing neurons in the canine medulla oblongata

Immunocytochemical methods were used to identify cells and processes containing two major catecholamine (CA)-biosynthetic enzymes in areas of the canine medulla implicated in autonomic control. Antisera were employed against tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT). These enzymes respectively catalyze the conversions of tyrosine to L-DOPA and noradrenaline to adrenaline. Immunocytochemical studies laid the groundwork for subsequent investigations in conscious dog in which we characterized an area of cardiovascular control in the rostral ventrolateral medulla (RVLM). In the anatomical studies, previously unidentified neuronal somata and processes were demonstrated in the canine medulla. Presumptive adrenergic (CI) neurons in the canine RVLM were subjacent to the nucleus ambiguous (NA) and most numerous at a level where the compact and semicompact divisions of NA merged. In contrast to their distribution in rodents, C1 neurons were skewed caudally and did not extend rostrally to the caudal pole of the facial nucleus. C1 neurons were also relatively less concentrated in the RVLM. A large number of C1 neurons extended dorsally into the lateral tegmental field (LTF). Most C1 neurons in the LTF (like those in the A1 area) were aligned with catecholaminergic (TH- and PNMT-ir) processes traversing the intermediate reticular zone. Since the numbers and locations of TH- and PNMT-ir neurons in the C1 area of the RVLM and rostral LTF were virtually identical on adjacent sections, it can be implicitly inferred that the enzymes are co-localized to the same somata and that these neurons are capable of biosynthesizing adrenaline. The C1 and A5 areas were clearly separated by a transitional zone, sparsely populated by TH-ir somata (1-2 cells per section), where the facial nucleus and rostral pole of the NA pars compacta (NAc) occupied the same level. A5 neurons were more abundant and complexly organized than suggested by previous CA-histofluorescence data. In addition, a new parvicellular subgroup was identified and composed of neurons containing TH but not PNMT. In contrast to other species, the A1 cell group was not confined to the VLM. A large number of A1 neurons extended into the caudal LTF and were situated between the nucleus tractus solitarii-motor vagal complex (NTS-X) and caudal VLM (CVLM). In contrast to previous reports, presumptive adrenergic (TH- and PNMT-ir) cell groups were more densely represented in the C2-3 areas of the canine NTS and dorsomedial reticular formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Transneuronal labelling of neurons in rabbit brain after injection of herpes simplex virus type 1 into the renal nerve

We mapped the distribution of virus-labelled neurons in the brain after injection of Herpes simplex virus type 1 (HSV1) into the rabbit renal nerve. Seven days after injection, labelled neurons were observed in four brain regions, the rostral ventrolateral medulla (47 +/- 3% of neurons), the A5 area of the lower pons (38 +/- 4%), the caudal raphe nuclei and the parapyramidal area of the medulla (13 +/- 2%), and the paraventricular nucleus of the hypothalamus (1 +/- 1%). In the rostral ventrolateral medulla approximately one half of the HSV1-labelled neurons also contained tyrosine hydroxylase, characterizing them as C1 neurons. In the A5 area virtually all HSV1-labelled neurons also contained tyrosine hydroxylase. In the raphe nuclei and the parapyramidal area 47% of HSV1-positive neurons contained serotonin. The distribution of labelled neurons was similar to that observed after injection of HSV1 into the adrenal gland.

Morphology and distribution of neuropeptide-containing neurons in human cerebral cortex

Biopsies of human cerebral cortex were fixed by immersion and immunostained for the detection of neuropeptides in neuronal cell bodies and axons. Four neuropeptides (neuropeptide Y, somatostatin, , substance P and cholecystokinin) were visualized in a series of adjacent sections. All populations of immunoreactive neurons had a morphology characteristic of interneurons, with variations in dendritic arborizations and laminar distribution. The cholecystokinin-immunoreactive neurons were most numerous in the supragranular layers, whereas neurons containing the other three peptides occurred mainly in infragranular layers, or even in neurons populating the subcortical white matter. Quantitatively, each population of neuropeptide-containing neurons accounted for 1.4-2.5% of the total neuronal population. The distribution of these neurons varied slightly between cytoarchitectonic divisions, with substance P- and somatostatin-immunoreactive neurons dominating in the temporal lobe and cholecystokinin-immunoreactive neurons in the frontal lobe. Neuropeptide Y-immunoreactive neurons dominated in the gray matter of the frontal half of the hemisphere and in the subcortical white matter of the caudal half of the hemisphere. Furthermore, co-existence of neuropeptide Y or substance P immunoreactivity within somatostatin-immunoreactive neurons could be demonstrated using double labeling immunofluorescence techniques. The axonal plexuses immunoreactive for neuropeptide Y, somatostatin, or substance P were distributed in all layers, with a strong predominance of horizontally oriented fibers in layer I, a moderate plexus of randomly oriented fibers in the supra- and infragranular layers, and a slightly weaker innervation of layer IV. Immunoreactive axons formed, in addition, complex terminal arbors, mostly in older subjects, suggesting that they resulted from an as yet undefined aging process. The present study underlines several aspects of the organization of the neuropeptide-containing neurons of the human cerebral cortex, which are of particular interest in the light of the involvement of these neurons in several neurodegenerative diseases.

gamma-Aminobutyric acid immunoreactive structures in the nucleus tractus solitarius: a light and electron microscopic study

gamma-Aminobutyric acid immunoreactive perikarya and boutons in the nucleus tractus solitarius of the cat were examined at both the light and electron microscopic level. Immunoreactive neurones were found predominantly in the parvocellular subdivision of the nucleus tractus solitarius and to a lesser degree in all the other subdivisions of the nucleus tractus solitarius and the dorsal vagal motonucleus. All the immunoreactive perikarya observed were similar in size and morphology. gamma-Aminobutyric acid immunoreactive boutons were observed throughout the nucleus tractus solitarius. However, in contrast to its high content of immunoreactive perikarya the parvocellular subdivision contained the lowest density of immunoreactive boutons. Ultrastructural examination of immunoreactive boutons in the different regions of the nucleus tractus solitarius revealed that they formed synaptic specializations, predominantly with dendritic shafts, all of which were of the symmetric type. This pattern of innervation was observed throughout the medial, commissural, ventrolateral and parvocellular subdivisions of the nucleus tractus solitarius.

Presumptive adrenergic neurons containing phenylethanolamine N-methyltransferase immunoreactivity in the medulla oblongata of neonatal swine

Given the importance of the swine (Sus scrofa) as an animal model for human development, physiology and disease, neurons containing the epinephrine-synthesizing enzyme, phenylethanolamine N-methyltransferase (PNMT), were mapped in the medulla oblongata of neonatal swine as a first step in identifying their roles in central autonomic control. Neurons were labeled immunocytochemically by using an antiserum to PNMT raised in rabbits against trypsin-treated enzyme purified from the bovine adrenal gland. The general regional organization of neurons expressing PNMT (-like) immunoreactivity (ir) in the neonatal swine was similar to data obtained in other species and, in some aspects, more closely resembled the pattern observed in the primate brain. Immunolabeled cells appeared to be more abundant and caudally more extensive than observed in other adult animals. PNMT-immunoreactive (ir) neuronal somata, however, were largely confined to the reticular formation in the ventrolateral quadrant and the nucleus tractus solitarii (NTS) and more restricted in distribution than those expressing tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (D beta H)-ir on serial transverse sections. A close correspondence was observed between the distributions of TH- and PNMT-ir neurons and processes throughout the C1 and C2 areas. However, in the C1 and C3 regions TH-ir neurons outnumbered those containing D beta H and PNMT-ir. In contrast, cell groups enriched in PNMT-ir neurons and processes were characterized by relatively weak D beta H-ir. In the ventrolateral medulla (VLM), PNMT-ir cell bodies were concentrated rostrally and extended from the caudal pole of the facial nucleus to a level posterior to the calamus scriptorius. The rostral VLM was characterized by an admixture of bipolar and multipolar primarily medium-diameter immunostained neurons. A prominent cell column (condensation) organized ventromedially to the nucleus ambiguus pars compactus (NAc). A loosely organized cluster bordered the lateral aspect of the special visceral efferent column; another smaller aggregate was located in the ventromedial reticular formation adjacent to the inferior olive. At middle medullary levels, PNMT-ir neurons formed two distinct subgroups (dorsal and ventral) interrupted by a band of precerebellar relay neurons that extended between the medial and lateral limbs of the lateral reticular nucleus of Walberg. At obex, the dorsal cell group formed a diagonal array and assumed a position dorsal and dorsolateral to the medial limb of LRN. This group was distinguished by bipolar neurons with axes of orientation directed perpendicularly to the majority of neurons in the rostal VLM or those lying near the caudal ventromedullary surface.(ABSTRACT TRUNCATED AT 400 WORDS)

Location and peptide content of pelvic neurons supplying the muscle and lamina propria of the rat vas deferens

Retrograde tracing and immunohistochemistry have identified the location within the rat pelvic plexus of neurons which project to the vas deferens, and their neurochemical properties. The fluorescent tracers, Fast Blue and FluoroGold, were injected into the wall of the vas deferens and labelled neurons located within the ventral part of the major pelvic ganglion (MPG) and the adjacent accessory ganglia (AG). Most neurons were located in ganglia ipsilateral to the injection site. Noradrenergic neurons were defined as those containing immunoreactivity for tyrosine hydroxylase (TH). Five groups of dye-labelled neurons could be identified immunohistochemically, noradrenergic neurons containing neuropeptide Y (NPY) (60-70%), and four types of non-noradrenergic neurons, NPY-only neurons (5-10%), NPY neurons containing vasoactive intestinal peptide (VIP) (3-5%), neurons containing only VIP (15-25%) and neurons containing galanin (GAL) (2-5%). Noradrenergic axons, and axons containing NPY or GAL were primarily located within the muscle, whereas most VIP axons were found as a dense plexus within the lamina propria. Very few peptide-containing varicose nerve terminals surrounded dye-labelled (vas deferens-projecting) pelvic neurons. Thus, no peptide marker was found for most of the preganglionic inputs supplying postganglionic neurons which project to the vas deferens. These studies have shown that pelvic neurons supplying the vas deferens have a discrete location within the rat pelvic ganglia and that they comprise at least five neurochemical groups, providing innervation to the muscle and lamina propria. The preganglionic connections with these noradrenergic and non-noradrenergic (possible cholinergic) pathways, and further examination of the role of mucosal innervation remain to be determined.

Changes in neuropeptide Y after experimental traumatic brain injury in the rat

We utilized a model of fluid percussion (FP) brain injury in the rat to examine the hypothesis that alterations in brain neuropeptide Y (NPY) concentrations occur following brain injury. Male rats (n = 44) were subjected to FP traumatic brain injury. One group of animals (n = 38) was killed at 1 min, 15 min, 1 h, or 24 h after brain injury, and regional brain homogenates were analyzed for NPY concentrations using radioimmunoassay. A second group of animals (n = 6) was killed for NPY immunocytochemistry. Concentrations of NPY in the injured left parietal cortex were significantly elevated at 15 min post injury (p less than 0.05). No changes were observed in other brain regions. NPY-immunoreactive fibers were seen at 15 min post injury predominantly in the injured cortex and adjacent hippocampus. These temporal changes in NPY immunoreactivity, together with previous observations concerning posttraumatic changes in regional CBF in these same areas, suggest that an increase in region NPY concentrations after brain injury may be involved in part in the pathogenesis of posttraumatic hypoperfusion.

[Leu31-Pro34] neuropeptide Y identifies a subtype of 125I-labeled peptide YY binding sites in the rat brain

Subtypes of the neuropeptide Y (NPY) receptor in the rat brain were identified by the use of the selective Y-1 analog, [Leu34-Pro34] NPY. In rat brain homogenate binding studies, [Leu31-Pro34] NPY was found to produce a partial inhibition of 100 pM 125I-labeled peptide YY (PYY) binding with a plateau at 50-1000 nM [Leu31-Pro34] NPY resulting in a 70% inhibition of binding. The C-terminal fragment NPY 13-36, a putative Y-2 agonist, exhibited very little selectivity in rat brain homogenates. Scatchard analysis of 125I-labeled PYY binding to rat brain homogenate yielded biphasic plots with Kd values of 40 and 610 pM. Inclusion of 100 nM [Leu31-Pro34] NPY was found to eliminate the low affinity component of 125I-labeled PYY binding leaving a single, high affinity binding site with a Kd of 68 pM. In autoradiographic studies, displacement curves indicated that [Leu31-Pro34] NPY completely inhibited binding in the cerebral cortex with little effect on the binding in the hypothalamus. On the other hand NPY 13-36 inhibited binding in the hypothalamus at low concentrations but required higher concentrations to inhibit binding in the cerebral cortex. Other brain regions such as the hippocampus, appeared to contain both subtypes. Subsequent to these studies, a quantitative autoradiographic map was conducted using 50-100 pM 125I-labeled PYY in the presence and absence of [Leu31-Pro34] NPY which produced a selective displacement of binding in certain distinct brain regions. These areas included the cerebral cortex, certain thalamic nuclei and brainstem while ligand binding was retained in other brain regions including the zona lateralis of the substantia nigra, lateral septum, nucleus of the solitary tract and the hippocampus. Numerous brain regions appeared to contain both receptor subtypes. Therefore, the Y-1 and Y-2 receptor subtypes exhibited a somewhat distinct distribution in the brain. In addition, 125I-labeled PYY appears to label the Y-2 receptor with relatively higher affinity when compared to the Y-1 receptor.

Ganglionic and arterial release of neuropeptide Y by bullfrog sympathetic neurons

Sympathetic C neurons in lumbar paravertebral ganglia of the bullfrog have previously been shown to be vasomotor in function and to express neuropeptide Y (NPY). In the present experiments, a sensitive radioimmunoassay was used to measure the NPY content of ganglia and the descending abdominal aorta and to measure the overflow of NPY evoked by depolarizing concentrations of K+. Paravertebral ganglia 9 and 10 contain 3.1 pg NPY/micrograms protein and the aorta contains 0.18 pg NPY/micrograms protein. During 20-min depolarizations in high K+ (58 mM) Ringer, the ganglia released approximately 5% of their NPY content and the aorta released approximately 2% of its NPY content. Pretreatment of the tissues with Ringer containing 0.18 mM Ca2+, 8 mM Mg2+, and 1 mM Co2+ blocked the NPY release elicited by high K+. These findings provide further evidence that NPY is a postganglionic co-transmitter in sympathetic C neurons of the bullfrog.

Dexfenfluramine treatment and hypothalamic neuropeptides in diet-induced obesity in rats

Neuropeptide Y (NPY) is a powerful appetite stimulant, and hypothalamic concentrations rise after food deprivation and in experimental diabetes. Serotonergic drugs such as dexfenfluramine are inhibitors of feeding. We measured hyothalamic NPY and NPY mRNA, along with galanin, neurotensin, and somatostatin in chow-fed rats and in rats with dietary obesity, and examined the effect of dexfenfluramine on these peptides in this model. Sixty-five rats were fed a palatable diet (condensed milk, sucrose and chow) for 6 weeks, which produced significant weight gain compared to twenty fed standard chow (145.1 +/- 2.3 g vs. 113.4 +/- 3.2 g, p less than 0.001). Groups of animals were treated for 7 days or 28 days with dexfenfluramine (1.8 mg/kg/day) or saline intraperitoneally via miniosmotic pumps. Hypothalami were dissected into medial and lateral blocks, and NPY, galanin, neurotensin, and somatostatin were measured by radioimmunoassay. Neuropeptide Y mRNA was measured by Northern blotting. Hypothalamic NPY was significantly higher in the palatable diet group compared to chow-fed controls (medial hypothalamus: 86.6 +/- 7.6 vs. 65.7 +/- 4.0 pmol/g tissue, p less than 0.02, lateral hypothalamus 71.2 +/- 6.6 vs. 53.1 +/- 3.6 pmol/g tissue, p less than 0.05), but NPY mRNA was unchanged. Although dexfenfluramine was effective at reducing weight gain in the animals fed the palatable diet, this did not result in any changes in the hypothalamic neuropeptides measured. Neuropeptide Y may be of importance in diet-induced obesity but the weight loss produced by dexfenfluramine in such animals is not mediated by changes in hypothalamic NPY.

Rostrocaudal differences in morphology and neurotransmitter content of cells in the subretrofacial vasomotor nucleus

The rostral ventrolateral medulla (RVLM) contains sympathoexcitatory neurons that exert a powerful control over the sympathetic outflow to the cardiovascular system. In the cat there is a concentration of such neurons (but not neurons subserving other functions) within a narrow longitudinal column in the RVLM termed the subretrofacial (SRF) nucleus. Furthermore, it has been suggested that there are subgroups of cells, located at different rostrocaudal levels of the SRF nucleus, that preferentially or exclusively control different vascular beds (e.g. in the kidney and hindlimb). The aim of this study was to map quantitatively the rostrocaudal distribution within the nucleus of different cell types, defined according to morphological and/or chemical criteria, and to correlate this with the regional vasomotor effects (in hindlimb and kidney) evoked by stimulation of SRF cells at the corresponding rostrocaudal levels. SRF cells were highly heterogeneous with respect to both their morphology and chemical properties. They varied greatly in size (equivalent diameter ranging from 10-40 microns) as well as in shape and orientation. An immunohistochemical examination using the avidin-biotin procedure revealed that many SRF cells (estimated 57% of all SRF cells) were immunoreactive for tyrosine hydroxylase (TH, a marker of catecholamine cells). In addition, there were SRF cells immunoreactive for neuropeptide Y (NPY, 11% of total), enkephalin (ENK, 16% of total), and serotonin (5HT, 10% of total), but not for substance P, galanin or somatostatin. Different cell types, defined according to their morphology and/or chemical properties, were unevenly distributed throughout the nucleus. In the most caudal part of the SRF nucleus, virtually all cells were TH-positive, and the large majority (estimated 80%) were NPY-positive, suggesting that many cells at this level contained both TH and NPY. In contrast, in the most rostral part of the SRF nucleus, only 30% of cells were TH-positive, and no NPY-positive cells were observed. Both 5HT- and ENK-positive cells were found throughout the rostrocaudal extent of the nucleus, but predominantly within its rostral part. Furthermore, TH-positive cells in the rostral SRF nucleus were on average significantly larger (mean equivalent diameter 18-43% greater) than TH/NPY-positive cells in the caudal part of the nucleus, but smaller than 5HT- or ENK-positive cells at the same level. Overall, rostral cells (regardless of their chemical type) were larger than caudal cells within the SRF nucleus (mean equivalent diameter 13-28% greater).(ABSTRACT TRUNCATED AT 400 WORDS)

Projections from rabbit caudal medulla to C1 and A5 sympathetic premotor neurons, demonstrated with phaseolus leucoagglutinin and herpes simplex virus

We combined Phaseolus vulgaris leucoagglutinin anterograde tracing and Herpes simplex virus transneuronal retrograde tracing to determine whether neurons in the vasodepressor region of the rabbit caudal ventrolateral medulla project to brainstem neurons containing the virus after its transneuronal transport from the adrenal medulla. Five days after adrenal injection of virus, 764 +/- 159 virus-positive neurons were found bilaterally in the brainstem: 61% in the C1 sympathoexcitatory region of the rostral ventrolateral medulla, 30% in the A5 region, 5% in the parapyramidal region, and 3% in the paraventricular nucleus of the hypothalamus. Many of the virus-positive neurons in the C1 and A5 areas also contained tyrosine hydroxylase and, in the parapyramidal area, many contained 5-hydroxytryptamine. After iontophoretic deposit of leucoagglutinin into the vasodepressor region of the caudal ventrolateral medulla, brain regions containing varicose processes labeled with leucoagglutinin included the regions containing virus-positive neurons. We examined the C1 and A5 regions following injections of both tracers in the same rabbits, leucoagglutinin into the caudal ventrolateral medulla and virus into the adrenal gland. Varicosities containing leucoagglutinin were seen in contiguity with perikarya and dendritic branches of neurons containing HSV1, in both the C1 and A5 regions. Studies also revealed labeled varicosities in contiguity with TH-containing C1 and A5 neurons. The projection from the caudal medulla to presumed sympathetic premotor neurons in the C1 area, including some C1 cells, represents a potential pathway whereby activity of neurons in the caudal medulla could reduce blood pressure by inhibiting sympathoexcitatory neurons in the rostral medulla.

Vasoactive intestinal polypeptide and acetylcholine coexist with neuropeptide Y, dopamine-?-hydroxylase, tyrosine hydroxylase, substance P or calcitonin gene-related peptide in neuronal subpopulations in cranial parasympathetic ganglia of rat

Immunohistochemistry has been used to demonstrate that neuropeptide Y, dopamine-beta-hydroxylase, calcitonin gene-related peptide or substance P are colocalized with vasoactive intestinal polypeptide and choline acetyltransferase in subpopulations of neurons in cranial parasympathetic ganglia of rat. These comprise the ciliary, sphenopalatine, otic, glossopharyngeal-vagal and internal carotid ganglia. In the ciliary and glossopharyngeal-vagal ganglia tyrosine hydroxylase is also found in such neurons. The findings emphasize that the combined localization of dopamine-beta-hydroxylase and neuropeptide Y or the presence of tyrosine hydroxylase is not exclusively a marker for peripheral adrenergic neurons. Further, the co-localization of calcitonin gene-related peptide and substance P is not a decisive indication that a neuron is sensory in nature. It is discussed whether the presence of the enzymes and peptides other than vasoactive intestinal polypeptide is a remnant of a different expression during ontogenesis or indicates target-specific functions in the adult.

Patterns of co-existence of peptides and differences of nerve fibre types associated with noradrenergic and non-noradrenergic (putative cholinergic) neurons in the major pelvic ganglion of the male rat

The pelvic ganglia supply cholinergic and noradrenergic nerve pathways to many organs. Other possible transmitters are also present in these nerves, including peptides. Multiple labelling immunofluorescence techniques were used in this study of the male rat major pelvic ganglion (MPG) to examine: (1) the peptides present in noradrenergic (tyrosine hydroxylase (TH)-positive) and non-noradrenergic (putative cholinergic) neurons, and (2) the types of peptide-containing nerve fibres closely associated with these two groups of neurons. The distribution of the peptide galanin (GAL) within the MPG was also investigated. All of the TH-neurons contained neuropeptide Y (NPY), but none of the other tested peptides. However, many NPY neurons did not contain TH and may have been cholinergic. TH-negative neurons also displayed vasoactive intestinal peptide (VIP), enkephalin (ENK) or GAL. VIP and NPY formed the most common types of putative cholinergic pelvic neurons, but few cells contained both peptides. Many ENK neurons exhibited VIP, NPY or GAL. Varicose nerve terminals surrounding ganglion cells contained ENK, GAL, somatostatin (SOM) and cholecystokinin (CCK). These peptide-immunoreactive fibres were more often associated with the non-noradrenergic (putative cholinergic) than the noradrenergic neurons; two types (SOM and CCK) were preferentially associated with the non-noradrenergic NPY neurons. GAL was distributed throughout the MPG, in small neurons, scattered small, intensely fluorescent (SIF) cells, and both varicose and non-varicose nerve fibres. The nerve fibres were concentrated near the pelvic and penile nerves; most of the varicose fibres formed "baskets" surrounding individual GAL-negative somata.

The time course of the development of the sympathetic innervation of the vasculature of the rat tail

The development of the sympathetic innervation of the tail vasculature in the rat has been examined using catecholamine fluorescence and immunohistochemical techniques to demonstrate tyrosine hydroxylase (TH) and neuropeptide Y (NPY). The tail was found to be largely devoid of noradrenergic terminals at birth. At the earliest ages, axons within nerve trunks and paravascular axon bundles showed high levels of catecholamine fluorescence, but this virtually disappeared as the innervation of the effectors was achieved. The perivascular plexus on the caudal artery was established over the first six postnatal weeks along a rostrocaudal gradient which was retained in the adult, i.e. proximal regions were more densely innervated than distal ones. The innervation of the rest of the vasculature developed relatively late during this period, with the exception of the arteriovenous anastomoses present in the distal half of the tail. These became innervated about 10 days earlier than the adjacent caudal artery at the same levels, and received a much denser innervation in the adult. At all developmental stages, distributions of TH- and NPY-immunoreactive nerve fibres were identical to those seen with catecholamine fluorescence. The sequence of development suggests that the different vascular targets are innervated by subsets of sympathetic neurons having the same neurochemistry but developing independently.

Electrophysiological properties of neurons in the rostral ventrolateral medulla of normotensive and spontaneously hypertensive rats

Single unit activities were recorded from the rostral ventrolateral medulla (RVL) of pentobarbital-anesthetized normotensive Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Throughout the recording period, arterial blood pressures of WKY (mean arterial pressure, MAP = 103.1 mm Hg) and SHR (MAP = 159.2 mm Hg) remained stable at the respective basal levels. The units recorded in this study were all spontaneously active and cardiac-locked. Two types of discharge patterns, namely single and double discharges, were identified. These single and double discharge units were found to distribute randomly in RVL. In WKY, 92.6% of RVL neurons exhibited single discharges whereas in SHR, the majority (57%) of RVL neurons exhibited double discharges. The mean firing rate of single discharge units in RVL of SHR was significantly higher than that of WKY, whereas the mean firing rate of double discharge units in WKY was similar to that of SHR. About half of the units studied were also tested for antidromic collision; all units tested could be antidromically activated from the intermediolateral column (IML) of the thoracic spinal cord and the lowest threshold sites were consistently localized within IML. In both groups of rats, the axonal conduction velocity of RVL neurons showed a bimodal distribution viz. the fast and slow conducting axons. The mean conduction velocities of each of these two groups of neurons in WKY and SHR were similar. Most of the double discharge units in WKY and SHR belonged to the fast conducting type.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunocytochemistry of thyrotropin-releasing hormone in the rabbit medulla oblongata

The distribution and ultrastructure of thyrotropin-releasing hormone-like immunoreactive (TRH-LI) neurons were examined in rabbit medulla oblongata. TRH-LI cell bodies were located in the ventral region of the medulla oblongata: in the paraolivary and parapyramidal regions, regions in and around the pyramidal tract, the dorsolateral region of the lateral reticular nucleus, and the raphe nuclei. The paraolivary and parapyramidal regions contained most of the TRH-LI cell bodies in the medulla oblongata. TRH-LI neurons processes were densely distributed in the dorsal vagal complex and the area postrema. Electron-microscopic immunocytochemical studies revealed TRH-LI neurons at the obex level in the paraolivary region of rabbits. TRH-like immunoreactivity was localized in larger granular vesicles. TRH-LI somata and dendrites received synaptic inputs from both TRH-LI and unlabeled axon terminals. More than half of the TRH-LI axon terminals made synapses with somata or processes of TRH-LI neurons. These observations, together with previous reports that TRH causes respiratory facilitation, suggest that TRH-LI neurons in the paraolivary region in rabbits may be involved in respiratory functions.

A comparative analysis of neurons containing catecholamine-synthesizing enzymes and neuropeptide Y in the ventrolateral medulla of rats, guinea-pigs and cats

Neurons in the ventrolateral medulla oblongata of rats, guinea-pigs and cats that contain tyrosine hydroxylase, dopamine-beta-hydroxylase, phenylethanolamine-N-methyltransferase and neuropeptide Y have been demonstrated immunohistochemically in serial coronal sections of tissue taken from the level of the cervical spinal cord to the level of the facial nucleus. The anatomical distribution of these neurons has been described, quantified and reconstructed in three dimensions to compare the neuron populations between species. In all species, between 50 and 90% of immunoreactive neurons lay rostral to the level of the obex. There were no significant differences in the number and distribution of neurons containing catecholamine-synthesizing enzymes between control animals and those pretreated with colchicine, with two exceptions: all dopamine-beta-hydroxylase neurons were weakly immunoreactive without colchicine pretreatment in cats, and pretreatment with colchicine revealed a small rostral group of tyrosine hydroxylase-positive neurons in guinea-pigs. There were remarkable similarities in the rostrocaudal distributions of neurons containing tyrosine hydroxylase, dopamine-beta-hydroxylase and neuropeptide Y in relation to comparable anatomical landmarks across the species. However, the distributions of neurons containing tyrosine hydroxylase. Phenylethanolamine-N-methyltransferase-positive neurons, while densely stained in rats, were only faintly stained in cats and absent in guinea-pigs; the distribution of these neurons was similar to the distribution of neurons containing only tyrosine hydroxylase. The similarity of the distribution of neurons demonstrated using tyrosine hydroxylase, dopamine-beta-hydroxylase and neuropeptide Y immunohistochemistry implies that homologous catecholamine-containing neuron groups do exist in the ventrolateral medulla despite the variation in phenylethanolamine-N-methyltransferase between species. In contrast to the previous classification of neuron groups into A1 and C1 based on the presence or absence of this latter enzyme, the data suggest that a discrete group of tyrosine hydroxylase-immunoreactive neurons, which probably do not contain dopamine-beta-hydroxylase or neuropeptide Y, can be distinguished in the rostral ventrolateral medulla of all species. The absence of detectable dopamine-beta-hydroxylase in this group of neurons suggests that they may not synthesize either adrenaline or noradrenaline.

Four groups of tyrosine hydroxylase-immunoreactive neurons in the ventrolateral medulla of rats, guinea-pigs and cats identified on the basis of chemistry, topography and morphology

The data in the preceding paper [Halliday G. M. and McLachlan E. M. (1991) Neuroscience 43, 531-550] suggest that some neurons in the rostral ventrolateral medulla contain some catecholamine-synthesizing enzymes but may not produce catecholamines. The present study addresses this question directly by comparing the anatomical location and morphology of these neurons with those revealed by formaldehyde-induced fluorescence. Catecholamine-containing somata of rats and guinea-pigs have been demonstrated following FAGLU-perfusion in normal untreated animals, in animals pretreated with pargyline (a monoamine oxidase inhibitor), and in animals pretreated with colchicine (to block axoplasmic transport). The number and location of fluorescent somata in the ventrolateral medulla have been determined in serial coronal sections of tissue from the cervical spinal cord to the level of the facial nucleus. Catecholamine-fluorescent neurons at different levels of the ventrolateral medulla varied in their topography and sensitivity to pharmacological manipulation. However, the rostrocaudal distributions in rats and guinea-pigs were quantitatively remarkably similar implying that homologous groups of catecholamine-containing neurons exist. Comparison between these distributions and those of somata stained immunohistochemically for catecholamine-synthesizing enzymes and neuropeptide Y [Halliday G. M. and McLachlan E. M. (1991) Neuroscience 43, 531-550] revealed that the majority of fluorescent neurons in both species probably contain dopamine-beta-hydroxylase and neuropeptide Y as well as tyrosine hydroxylase. Those neurons lying just caudal to the facial nucleus immunoreactive for tyrosine hydroxylase and phenylethanolamine-N-methyltransferase but not dopamine-beta-hydroxylase and neuropeptide Y also lack catecholamine fluorescence. This rostral group of somata can be identified immunohistochemically in cats. The size and morphology of catecholamine-fluorescent neurons have been analysed in detail, and compared with the same features of the immunohistochemically stained neurons. Three morphological types of catecholamine-containing neurons could be distinguished in material prepared by both techniques from rats and guinea-pigs, and in immunohistochemical material from cats. Rostral tyrosine hydroxylase-positive neurons, which differed morphologically from these three types, were present in all three species. On the basis of anatomical location, neuronal morphology and chemical characteristics, four groups of tyrosine hydroxylase-immunoreactive neurons have been identified in the ventrolateral medulla of rats, guinea-pigs and cats. Only the caudal three of these four groups appear to synthesize catecholamine, probably noradrenaline. From published data it seems likely that these four groups of tyrosine hydroxylase-positive neurons have distinct projections and functions related to cardiovascular and respiratory control.