GAL-immunoreactive Fibers Research Articles

Characteristics of galanin and vasoactive intestinal peptide immunoreactivity in the rat amygdala complex

Morphological features and morphometric parameters of galanin (GAL) and vasoactive intestinal peptide (VIP) immunoreactive neurons and neuronal fibres were studied in all nuclei of adult male rat amygdala. After perfusion and fixation, rat brains were immunohistochemically stained with antibodies against GAL and VIP and then visualized by avidin-biotin-peroxidase complex. The greatest number of galanin-immunoreactive neurons were identified in the medial part of the central nucleus and in the dorsal part of the medial nucleus. In the first case, most neurons were bipolar (37%), and in the second, they were ovoid (45%). GAL-immunoreactive fibers were identified in the medial nucleus, "bed nucleus" of the accessory olfactory tract, fiontal cortical nucleus, amygdalo-hippocampal area and basolateral nucleus. VIP-immunoreactive neurons were diffusely distributed in more nuclei than the previous, mostly in the lateral, basolateral, and basomedial nucleus. They were mostly ovoid (40%). VIP-immunoreactive fibers were observed in the lateral part oJ'the central nucleus, while long and radially oriented fibers were present in the frontal and dorsal cortical nucleus. By distribution analysis of GAL and VIP immunoreactive neurons and fibers, and according to literature data, it can be assumed that the medial part of the central nucleus receives VIP fibers from other parts of the amygdaloid body, and then sends GAL fibers to the medial nucleus.

Galanin-like immunoreactivity in the brain and pituitary of the "four-eyed" fish, Anableps anableps.

The distribution of galanin (GAL)-like immunoreactivity was investigated in the brain and pituitary of the "four-eyed" fish, Anableps anableps. GAL-immunoreactive (GAL-ir) perikarya were located in the area ventralis telencephali pars supracommissuralis, nucleus preopticus periventricularis, nucleus preopticus pars parvocellularis, nucleus preopticus pars magnocellularis, nucleus lateralis tuberis ventralis, nucleus lateralis tuberis lateralis, and nucleus lateralis tuberis posterior. A few scattered, GAL-ir neurons were also observed in or adjacent to the nucleus recessus lateralis, nucleus recessus posterioris and lobus facialis (VII). GAL-ir fiber networks were widespread in the brain, with a comparatively higher density in the ventral telencephalic, preoptic and infundibular regions. The neurohypophysis showed GAL-ir innervation and there were GAL-ir cells in the adenohypophysis. The presence of GAL-ir cells in the hypothalamus and in the pituitary is an important asset for the supposed role of GAL-like peptide in neuroendocrine regulation of brain and pituitary functions.

Origin, distribution, and morphology of galaninergic fibers in the rodent trigeminal system.

The neuropeptide galanin (Gal) is found throughout the central nervous system. Of particular interest is the fact that Gal is present within the majority of noradrenergic locus coeruleus (LC) neurons. However, very few, if any, Gal-immunoreactive fibers have been identified in many of the major efferent targets of LC, including sensory neocortex and dorsal thalamus. The goal of the present study was to examine the Gal fiber innervation of the rodent trigeminal somatosensory system and its connection to the LC. Our results show that at least two different morphological profiles of Gal-immunoreactive fibers are present within relay nuclei along the ascending trigeminal pathway. Numerous small caliber Gal-immunoreactive fibers with bouton-like swellings were noted within the barrel cortex, the ventroposterior medial (VPM) nucleus, the posterior medial (POm) nucleus, the zona incerta (ZI), the reticular nucleus (nRT) of the thalamus, and the principal (PrV) and spinal (SpV) nuclei of the trigeminal complex. Immunoreactive fibers were prevalent in, but not restricted to, layer I of the barrel cortex. Within the somatosensory thalamus, the density of Gal-immunoreactive fibers was higher in POm than in VPM. Laminae I and II of SpV and the nRT and ZI also contained dense, large-diameter Gal-immunoreactive fibers. These large-diameter Gal-immunoreactive fibers did not co-contain dopamine beta-hydroxylase (DBH). In contrast, virtually every small-caliber Gal-immunoreactive fiber colocalized with DBH. To determine whether Gal-immunoreactive fibers originated from LC, we combined immunohistochemical procedures with fluorescent tracing techniques. After retrograde tracer injections into several trigeminal relay nuclei, we observed that approximately 50% of the labeled LC neuronal population was immunoreactive for Gal. Our results suggest an extensive Gal-immunoreactive fiber innervation of the rodent trigeminal system, much of which may originate from LC neurons in the brainstem.

Distribution of neuropeptide-containing nerve fibers in the salamander taste organs.

Salamander taste organs were recognized as oval cell clusters within the dorsal surface of the tongue. A moderate number of SP, CGRP, VIP, NPY, and GAL immunoreactive nerve fibers terminated in the cell clusters, and some of them penetrated into the basal half of the cell clusters. Around the glands, VIP, NPY, and GAL fibers were numerous, and SP and CGRP fibers were less numerous. Immunoreactivity of SOM and FMRF was not detected either in the nerve fibers associated with the cell clusters or those around the glands. These findings suggest that the chemosensory mechanisms of the salamander gustatory organs are under the control of peptidergic innervation. In addition, the present study indicates that the caudate taste organs are structurally primitive but functionally mature.

Semiquantitative distribution of galanin-receptor (GAL-R1) mRNA-containing cells in the male rat hypothalamus.

The semiquantitative distribution of mRNA encoding for rat galanin receptor (GAL-R1) was examined by in situ hybridization in the rat hypothalamus using a 35S-riboprobe. Most hypothalamic nuclei expressed GAL-R1 mRNA. In the anterior hypothalamus, high levels of expression were found in the medial preoptic area, paraventricular and supraoptic nuclei. Numerous cells also expressed the GAL-R1 mRNA with a moderate level of expression in the periventricular region. Very few GAL-R1-expressing cells were present in the suprachiasmatic nucleus. In the medial hypothalamus, numerous expressing cells were detected in the dorsomedial and ventromedial nuclei. The arcuate nucleus was moderately labeled throughout its rostrocaudal extent; labeled cell bodies were visible in the ventromedial and ventrolateral subdivisions as well. These results indicate that the GAL-R1 mRNA is not only expressed in anterior hypothalamic nuclei but also in the mediobasal hypothalamus and periventricular region. This hypothalamic distribution correlates well with that of 125I-GAL-binding sites and GAL-immunoreactive fibers. This distribution represents the morphological substrate for GAL roles in the hypothalamic regulation of neuroendocrine, behavioral and autonomic functions.

Distribution of galanin-immunoreactive nerve fibers in the carotid labyrinth of the bullfrog, Rana catesbeiana: comparison with substance P-immunoreactive fibers

Immunoreactivity of galanin (GAL) was detected in the nerve fibers distributed within the intervascular stroma of the bullfrog carotid labyrinth. GAL-immunoreactive fibers are numerous, and some are close to the sinusoidal plexus. Most GAL fibers appear as thin processes with some varicosities. A combination of indirect double immunofluorescence labelling and image processing clearly demonstrated that the distribution pattern of GAL fibers is different from that of SP fibers. This indicates that GAL and SP do not coexist in the same nerve fibers. The role of GAL fibers may be different from that of previously reported neuropeptides (substance P, calcitonin gene-related peptide, vasoactive intestinal polypeptide, neuropeptide Y, and others) as a neuromodulator in controlling vascular tone of the labyrinth.

Distribution and chromatographic analysis of galanin immunoreactivity in the heart

The presence and distribution of the biologically active neuropeptide galanin (GAL), in the rat heart as well as in mouse, guinea pig, rabbit, cat, and dog heart, were analyzed. With some minor variations in the overall distribution, extractable GAL-like immunoreactivity (-LI) was present in all major portions of the heart. In the rat heart, GAL-immunoreactive (GAL-IR) nerve fibers were present in the atria as well as in the ventricles; thin GAL-IR fibers were present in the myocardium as well as around some cardiac blood vessels. A few larger GAL-IR nerve fiber bundles were also present on the surface of the heart. Characterization of extractable GAL-LI in the rat heart, using HPLC, revealed one GAL-IR form, coeluting with synthetic rat GAL. Our findings suggest that galanin is of importance in the control of certain cardiac functions and/or of circulation.

Galanin-immunoreactivity in the nucleus basalis of Meynert in the rat: Age-related changes and differential response to lesion-induced cholinergic cell loss

The neuropeptide Galanin (Gal) is known to play a functional role in the basal forebrain cholinergic system. In our study, the morphology and density of the Gal-immunoreactive (Gal-IR) fiber network within the cholinergic nucleus basalis of Meynert (NBM) was investigated 1, 3 and 6 months after stereotaxic lesion with quisqualic acid in young adult (3 months old) and late middle-aged (20 months old) rats. Quantitative densitometry showed a significantly reduced Gal-IR fiber network in 20-month-old control rats. After lesion-induced cholinergic cell loss, no further changes in Gal-IR were noted in this group of aging rats during the period of investigation. In contrast, young adult animals displayed a significant increase of Gal-IR fiber density 6 months after NBM lesion. However, no hyperinnervation of individual surviving cholinergic neurons was seen. The results obtained in an animal model of cholinergic deficit support the hypothesis of age-related neuroplasticity of specific transmitter and peptide systems. Adaptive changes in Gal may play a role for the modulation of cholinergic function and could be of importance in human age-related neurodegenerative disorders, i.e. Alzheimer's disease.

<b>DISTRIBUTION OF GALANIN IMMUNOREACTIVE FIBERS IN THE MOUSE VOMERONASAL </b><b>ORGAN </b>

Galanin (GAL)-immunohistochemical techniques were applied to the mouse vomeronasal organ. GAL-immunoreactive fibers were seen in the receptor-free epithelial region, but no fibers were found in the neuroepithelial region. Many GAL-immunoreactive fibers were distributed around the cavernous blood vessels and the vomeronasal glands, and these fibers had a large number of varicosities and branches. GAL-immunoreactive fibers were also distributed in both the olfactory epithelial area and the respiratory epithelial area. GALimmunoreactive cell bodies were seen in the trigeminal ganglion, in the sphenopalatine ganglion, and in the superior cervical ganglion

Identification of galanin-immunoreactive cells in the anterior pituitary of male monkeys (Macaca fascicularis).

The localization of galanin (GAL) was studied in the anterior pituitary of adult male macaque monkeys immunohistochemically. GAL-immunoreactive fiber bundles were noted in the posterior lobe of the pituitary. Cells immunoreactive for GAL were observed in the anterior lobe, and colocalization studies revealed that GAL-like immunoreactivity was present in gonadotrophs and thyrotrophs. The differences among the monkey, human and rat in GAL-immunoreactive localization may indicate that the regulation of GAL in the three species differs.

Galanin receptors in the brain of a teleost: autoradiographic distribution of binding sites in the Atlantic salmon.

The distribution of galanin (GAL) binding sites in the brain of the Atlantic salmon (Salmo salar) was investigated by means of radioligand binding in conjunction with autoradiography by using high-performance liquid chromatography (HPLC) characterized radio-iodinated porcine galanin ([125I]GAL). On slide-mounted sections of frozen salmon brain homogenate, [125I]GAL (4 nM) bound rapidly and reversibly to a single population of sites with a Kd of 1.0 +/- 0.08 nM (n = 3) and Bmax of 2.38 +/- 0.19 fmol/mg wet tissue. Specific [125I]GAL binding was found in cellular regions, in fiber tracts, and in neuropil areas throughout the brain, except for in the olfactory bulb, pineal organ, and cerebellum. Autoradiographic microdensitometric measurements revealed high total [125I]GAL binding in the ventral hypothalamus (inferior lobes; around 7-12 fmol/mg tissue), the dorsal spinal cord (between 6 and 12 fmol/mg tissue), sublayers of the optic tectum (around 8 fmol/mg), torus semicircularis (around 7 fmol/mg), and glomerular complex (around 6 fmol/mg). Intermediate densities of [125I]GAL binding (3-5 fmol/mg tissue) were found in the pituitary, telencephalon, dorsolateral thalamic nucleus, and raphe nuclei and in association with the forebrain bundles. Except for in the optic tectum, there is a good concordance of [125I]GAL binding sites and GAL-immunoreactive fiber projections in most brain areas of the salmon. The wide distribution of GAL binding sites provides further evidence that a GAL-like substance might be involved in a diversity of brain functions of teleosts. The topographic distribution of target sites in the hypothalamo-hypophyseal axis indicates that GAL-like substances may have both direct and indirect effect on pituitary functions while in extrahypothalamic areas, functional implications by GAL may include involvement in somatosensory, central gustatory, olfactory, and visual functions. This study provides evidence for the presence of a specific GAL receptor in the brain of the Atlantic salmon. Together the distribution of GAL binding and GAL-like molecules provide a covering delineation of the GAL neuronal system in the brain of the Atlantic salmon. Comparisons with mammals suggest that the GAL receptor molecule has been well preserved during evolution and that GAL-like substances may be present, and even possess similar functional properties, throughout the vertebrate phylogeny.

Distribution and origin of extrinsic nerve fibers containing calcitonin gene-related peptide, substance P and galanin in the rat upper rectum

The distributions of nerve fibers containing calcitonin gene-related peptide (CGRP), substance P (SP) and galanin (GAL) were examined in the rat rectum of mutants rats, aganglionic rats (AGRs), which completely lack the intramural nerve cells in the large intestine, and of their normal littermates. The origin of extrinsic peptide-containing nerve fibers was examined using retrograde tracing combined with immunohistochemistry in normal rats. In the rectum of normal rats, CGRP-, SP- and GAL-immunoreactive varicose fibers were observed throughout all layers of the rectal wall, and immunoreactive nerve cells were present in the enteric ganglia of colchicine-treated rats. In the aganglionic rectum of AGR, a rich supply of CGRP-immunoreactive fibers was observed in the mucosa, around the blood vessels, and in the submucous and intermuscular spaces. SP- and GAL-immunoreactive fibers in the aganglionic rectum showed a similar distribution to CGRP-immunoreactive fibers but were less dense. These results suggest that most of CGRP-positive fibers in the rectum are extrinsic whereas a large part of SP- or GAL-positive fibers are intrinsic. Fluoro-gold injected into the upper rectum of normal rat labelled nerve cells (less than 10% of total ganglion cells) in the lumbar (L 1 and L 2) and lumbosacral (L 6 and S 1) dorsal root ganglia. More than half of nerve cells in the dorsal root ganglia (L 6 and S 1) projecting to the rectum were immunoreactive for CGRP, and less than 10% were immunoreactive for SP or GAL. Comparison of serial sections of the dorsal root ganglion revealed that about half of the CGRP-immunoreactive cells were also positive for SP or GAL. These results indicate that SP- or GAL-positive neurons projecting to the rectum are scarce in the dorsal root ganglia. The present investigation suggests that CGRP-containing nerves are visceral afferents forming a major component of the sensory innervation of the rat rectum, and SP- and GAL-containing nerves which share their extrinsic origins appear to form a lesser proportion of the sensory innervation.

Deficit of galanin-like immunostaining in the median eminence of adult hypothyroid rats.

In this paper we describe the modification of the galanin (GAL)-like immunostaining in the hypothalamus of rats, which were made hypothyroid at 52 days after birth. On 21st day after the surgical ablation of the thyroid gland, the staining of the GAL-immunoreactive fibers in the median eminence decreased and on the 84th day disappeared almost totally. The GAL-immunoreactive distribution in other areas of the hypothalamus, e.g. the anterior hypothalamus and the dorsomedial nucleus, is only slightly affected by the absence of thyroid hormones, whereas the GAL-staining of medulla oblongata (vagal complex) is equal in both control and hypothyroid rats. In hypothyroid colchicine-treated rats, we were unable to stain GAL-immunoreactive neurons in the paraventricular nucleus (PVN). Oxytocin- and vasopressin-like material was present in the magnocellular neurons and the staining pattern in hypothyroid rats was the same as that of control animals. Our data show a marked reduction in the expression of the GAL-like immunoreactivity of the PVN and median eminence of adult hypothyroid rats. The possible role of this deficit in the pathogenesis of the GH secretion impairment that is observed in hypothyroid rats is discussed.

Galanin immunoreactivity in the blowfly nervous system: Localization and chromatographic analysis

In this study chromatographic, immunochemical, and immunocytochemical methods provide evidence of a galanin-like peptide(s) in an invertebrate, the blowfly Phormia terraenovae. The major portion of the galanin-like immunoreactivity (GAL-LI) in fly heads was extractable in acetic acid but not in boiling water, which suggests that the peptide(s) may be highly basic in nature. GAL-LI was present both in the head and body portion of the blowfly in roughly the same amounts. Initial gel filtration data, using a G-50 Sephadex column and a weak phosphate-buffer (pH 6.5) as eluent, suggested that a fly GAL-LI peptide(s) from fly heads, eluting as an apparent single peak, was smaller than porcine GAL(1-29) and GAL(1-15). However, concomitant analysis using a G-25 Sephadex column and acetic acid (0.2 M) as eluent, spread the immunoreactive material over a great portion of the chromatogram, although the main portion of the material eluted in the same size range as porcine GAL(1-29). Taken together, the gel filtration data thus suggest that fly GAL-LI peptide(s) may be highly basic but presumably similar in size to vertebrate GAL(1-29). However, the hydrophobic properties of the fly GAL-LI peptide(s) differ from that of porcine GAL as demonstrated by the presence of several immunoreactive components eluting both early as well as late in the chromatogram when using reverse-phase high performance liquid chromatography (HPLC); early peaks may represent highly basic and/or possibly smaller GAL-immunoreactive peptide(s), whereas later peaks may represent less basic and possibly elongated forms. Immunocytochemistry indicated that GAL-LI was present in the nervous system of the blowfly. About 160 GAL-immunoreactive neurons were found in the brain and subesophageal ganglion, 26 in the fused thoracic ganglion and 30 in the fused abdominal ganglion. In the brain, GAL-immunoreactive fibers supply specific subdivisions of the central body, optic lobe, superior protocerebrum, and tritocerebrum as well as neuropil in the subesophageal ganglia. In the thoracico-abdominal ganglia, GAL-immunoreactive neuron processes are found inside synaptic neuropil as well as in the neural sheath of the ganglia and several of the dorsal nerve roots. Many of the GAL-immunoreactive neurons react also with an antiserum against porcine galanin message associated peptide, a peptide present in the preprogalanin protein. Immunocytochemical double-labeling indicated that some GAL-immunoreactive neurons also reacted with antisera against the molluscan peptides FMRFamide and SCPB, whereas no evidence could be found for colabeling with antisera against tyrosine hydroxylase, substance P and physalaemin.(ABSTRACT TRUNCATED AT 400 WORDS)

Neurokinin A and Galanin in the Thyroid Gland: Neuronal Localization*

The distribution of neurokinin A (NKA) and galanin (GAL) in the thyroid gland of several species was examined with immunocytochemistry. NKA-immunoreactive fibers were observed around blood vessels and follicles in all species examined, whereas GAL-immunoreactive fibers were found in mice and rats only. NKA-containing fibers were more numerous than GAL-containing fibers. All thyroid NKA-containing fibers harbored substance P (SP), and the majority of them stored calcitonin gene-related peptide (CGRP) as well. Most thyroid GAL-immunoreactive fibers contained NKA, SP, and CGRP; in a minor population GAL coexisted instead with vasoactive intestinal peptide. Cervical vagotomy (extirpation of the nodose ganglion) reduced the number of NKA- and GAL-containing fibers in the thyroid by approximately 50%. The jugular ganglion and cervical dorsal root ganglia are fairly rich in GAL-, NKA/SP-, and CGRP-containing cell bodies, which presumably represent the source of GAL-, NKA/SP-, and CGRP-containing fibers in the thyroid. The thyroid ganglion is rich in vasoactive intestinal peptide nerve cell bodies, which presumably project to the thyroid gland; a minor proportion of these cell bodies was found to contain GAL as well. Although the distribution of NKA and GAL fibers in the thyroid suggests that the two peptides are involved in the regulation of local blood flow and follicular cell activity, neither NKA nor GAL had any influence on thyroid hormone release as tested in conscious mice.