Density Of Immunoreactive Fibers Research Articles

The somatostatin system of the brain and hibernation in the European hamster (Cricetus cricetus).

The depression of physiological processes characteristic of mammalian hibernation is precisely regulated by the central nervous system, especially by the neuropeptidergic apparatus of the hypothalamus. Because of inhibitory influences on neuronal circuits within the brain and suppressive effects on the metabolism via the endocrine axis, somatostatin has been implicated in the regulation of hibernation. The somatostatin system of the brain was investigated with immunocytochemistry, in situ hybridization, and radioimmunoassays in euthermic summer, euthermic winter, and hibernating European hamsters (Cricetus cricetus). Numerous somatostatin-immunoreactive perikarya were observed in the periventricular hypothalamic nucleus. The striatum, amygdala, and cortex contained only scattered immunoreactive perikarya. These entities also contained immunoreactive fiber profiles, although the highest density of immunoreactive fibers was found in the median eminence. Immunocytochemistry and radioimmunoassays showed that the number of somatostatin-immunoreactive perikarya and fibers and the content of somatostatin in the hypothalamus and the median eminence was conspicuously lower in euthermic winter animals than in euthermic summer animals. This decrease was more pronounced in hibernating specimens. In situ hybridization also demonstrated a decrease in the expression and synthesis rate of somatostatin in euthermic winter animals; again, this was even more dramatic in hibernating hamsters. These changes were less pronounced or non-significant in the extrahypothalamic somatostatin-immunoreactive perikarya and fiber systems, as shown by immunocytochemistry and radioimmunoassay, respectively.

ACTH/CLIP Immunoreactivity in the Cat Brain Stem

COVEÑAS, R., M. de LEÓN, J. A. NARVÁEZ, J. A. AGUIRRE, G. TRAMU AND S. GONZÁLEZ-BAŔON.ACTH/CLIP immunoreactivity in the cat brain stem.PEPTIDES 18(7) 965–970, 1997.—The distribution of adrenocorticotropin hormone/corticotropin-like intermediate lobe peptide was studied in the cat brain stem, using an indirect immunoperoxidase technique. No immunoreactive cell bodies were observed. However, a high density of immunoreactive fibers was found in the periaqueductal gray, the dorsal nucleus of the raphe, the locus coeruleus, and the marginal nucleus of the brachium conjunctivum. A moderate density was found in the central linear nucleus, the central tegmental field, the Kölliker–Fuse nucleus, the inferior central nucleus, and the postpyramidal nucleus of the raphe. A low density was found in the superior and inferior colliculi, the interpeduncular nucleus, the nucleus sagulum, the superior central nucleus, the cuneiform nucleus, the accessory dorsal tegmental nucleus, the nucleus of the solitary tract, the dorsal motor nucleus of the vagus, and the paralemniscal, magnocellular, gigantocellular, and lateral tegmental fields. Moreover, single immunoreactive fibers were observed in numerous nuclei of the cat brain stem. In comparison with previous studies carried out in the same region of the cat, as well as the rat and the human, our results point to a more widespread distribution of adrenocorticotropin hormone/corticotropin-like intermediate lobe peptide immunoreactive structures in the cat brain stem. This widespread distribution indicates that the peptide might be involved in several physiological functions of the cat brain stem.

An immunocytochemical mapping of ACTH/CLIP in the cat diencephalon

Using an indirect immunoperoxidase technique, the location of cell bodies and fibres containing adrenocorticotropin hormone/corticotropin-like intermediate lobe peptide (ACTH/CLIP) was studied in the cat diencephalon. Immunoreactivity was observed in several diencephalic nuclei of the cat in which no immunoreactivity has been previously reported. In this sense, a low density of immunoreactive cell bodies was found in the nucleus ventromedialis hypothalami; a high density of immunoreactive fibres was found in the medial preoptic area; a moderate density in the lateral preoptic area and in the nuclei centralis thalami (pars medialis), interventralis thalami, interanteromedialis thalami, parafascicularis and praemamillaris (pars ventralis and pars dorsalis); a low density in the nuclei habenularis lateralis and reuniens thalami, and single fibres were found in the nuclei lateralis thalami (pars anterior), habenularis medialis, parataenialis, corpus geniculatum mediale, ventralis thalami (pars medialis) and in the fornix. Our results point to a more widespread distribution of ACTH/CLIP immunoreactive structures in the cat diencephalon in comparison with previous studies carried out in the same region of this feline.

Distribution of substance P and calcitonin gene-related peptide immunoreactive nerve fibers in the trachea of chronically hypoxic rats

The distribution of substance P and calcitonin gene-related peptide immunoreactive nerve fibers in the trachea was compared between normoxic and chronically hypoxic rats (at 380 mm Hg for 10 weeks). In the normoxic trachea, the immunoreactivity to either peptide was seen in the nerve fibers in four principal locations: a) within and b) under the ciliated epithelium, c) within the smooth muscle bundles in the posterior wall, and d) in the connective tissue and around blood vessels in the lamina propria and submucosa. These immunoreactive fibers within the epithelium and smooth muscle bundles, in the connective tissue, and around blood vessels were thin and displayed some varicosities, and those under the epithelium appeared as thick nerve bundles. When the distribution and density of immunoreactive fibers were compared between normoxic and chronically hypoxic tracheas, there was a difference in number of substance P and calcitonin gene-related peptide immunoreactive fibers penetrating into the epithelium, although there was no difference in the other three locations. The mean number of substance P and calcitonin gene-related peptide immunoreactive intraepithelial fibers per section of the chronically hypoxic trachea was significantly increased. Because substance P and calcitonin gene-related peptide are predominant signal peptides of primary sensory neurons, the increase of substance P and calcitonin gene-related peptide immunoreactive fibers suggests that altered airway reflexes may be a feature of hypoxic adaptation.

Assessment of volumetric sex differences in the song control nuclei HVC and RA in zebra finches by immunocytochemistry for methionine enkephalin and vasoactive intestinal polypeptide

In this study we assessed sex differences in the volume of two vocal control nuclei, the high vocal center (HVC) and the robust nucleus of the archistriatum (RA) in zebra finches ( Taeniopygia guttata) exposed to various endocrine treatments (neonatal treatment with an aromatase inhibitor and/or an adult treatment with testosterone). The boundaries of these nuclei were defined in sections stained for Nissl substance and compared to alternate sections stained with an immunocytochemical procedure for two neuropeptides, methionine enkephalin and vasoactive intestinal polypeptide. A high density of immunoreactive fibers for methionine enkephalin and vasoactive intestinal polypeptide completely covered the high vocal center in male and female zebra finches and these fibers were not observed in the surrounding neostriatum. With the use of these markers to define the boundary of the high vocal center, it became possible to reconstruct its volume. Positively staining perikarya were not apparent within the boundaries of this nucleus. Immunoreactive fibers for vasoactive intestinal polypeptide and enkephalin also allowed one to define the boundary of the robust nucleus of the archistriatum but they did not fill the entire area of the nucleus as is the case for the high vocal center. When the volumes of both nuclei were reconstructed based on enkephalin or vasoactive intestinal polypeptide immunoreactivity, the presence of a marked sex difference in the volume of these nuclei was confirmed. Neonatal and adult endocrine manipulations did not affect the volumes of these two nuclei measured in Nissl-stained material nor did they affect the volumes as defined based on the peptidergic innervations of the nuclei. Also, the volumetric estimates of these two nuclei derived from sections stained by immunocytochemistry were in good agreement in all groups of birds with the values obtained based on an analysis of the Nissl-stained material. These results illustrate the usefulness of employing a variety of histochemical markers to define a brain area when investigating brain variation and plasticity.

Plasticity of mature sensory cerebrovascular axons following intracranial infusion of nerve growth factor.

Mature perivascular sympathetic axons associated with the intradural segment of the internal carotid artery (ICA) of the adult rat respond by sprouting following a two week infusion of nerve growth factor (NGF) into the lateral ventricle of the brain. Because nonsympathetic axons such as those comprising the sensory and parasympathetic population have been shown to respond to NGF, the present study was carried out to determine whether mature sensory axons respond to in vivo NGF infusion and whether competitive interactions between the innervating populations might affect the responsiveness of these axons to NGF. Standard electron microscopic techniques as well as calcitonin-gene-related peptide (CGRP) immunohistochemistry at the light microscopic level were used to examine the effects of intracerebroventricular NGF infusion on mature perivascular fibers with and without prior sympathetic denervation (i.e., bilateral superior cervical ganglionectomy). Following NGF infusion, CGRP-immunoreactive fibers appeared thicker and more numerous in the longitudinal plane when compared with vehicle controls. However, at the ultrastructural level, a significant increase in the total number of axons was not observed, although there was an increase in the number of large granular vesicles, suggesting that the CGRP fibers responded to exogenous NGF with an increase in neurotransmitter content, but not by sprouting. Sympathetic denervation, on the other hand, resulted in a significant increase in the number of fibers passing in the circumferential plane. The most dramatic change in CGRP immunoreactivity was observed following combined sympathetic denervation and subsequent NGF infusion, where, in addition to the presence of thicker immunoreactive fibers, a significant increase in the perivascular density of immunoreactive fibers associated with the intradural blood vessels was observed. These findings suggest that exogenous NGF has different effects on mature sympathetic and nonsympathetic fibers that innervate intradural blood vessels. The former exhibit robust sprouting, whereas the latter do not sprout in response to NGF but show evidence for increased neuropeptide content. In addition, the heightened response by sensory axons following denervation and subsequent NGF infusion provides support for the idea that sensory and sympathetic axons normally compete for target space and/or target-derived neurotrophic factors.

Gonadal steroid hormone-dependence of β-endorphin-like immunoreactivity in the medial preoptic area of the rat

Gonadal steroid hormones are known to alter the expression of proopiomelanocortin (POMC) mRNA in neurons of the arcuate nucleus (ARC). These neurons send projections to the medial preoptic area (MPOA), wherein μ-opiate receptor density is cyclical and gonadal steroid hormone-dependent. Although β-endorphin-(β-Endo) content in the MPOA is known to vary across the estrous cycle, the effect of gonadal hormones on the distribution and density of β-Endo-like immunoreactive (IR) fiber density in the preoptic area is unknown. In the present study, immunohistochemical staining was used to investigate the effects of gonadal steroid hormone treatment on β-Endo-like IR fibers in the MPOA of ovariectomized (OVX) female rats. The density of β-Endo-like IR fibers was low in the MPOA of OVX rats, but increased slightly following treatment with 17β-estradiol (E 2) or 3 h after subsequent progesterone (P) injection. However, β-Endo-like IR fiber density increased significantly 27 h after E 2P treatment, and remained elevated 51 h after E 2P treatment in the periventricular zone and in the medial portion of the medial preoptic nucleus, although the general distribution of fibers was unchanged. These results suggest that the density of MPOA β-Endo innervation is normally gonadal steroid hormone-dependent and that the medial MPOA contains greater opioid tone than the lateral MPOA regardless of the hormonal state. Furthermore, since β-Endo-like IR fiber density remained elevated even though gonadal hormone levels decreased, additional factors might modulate the release or turnover of β-Endo in the MPOA during normal estrous cycling.

Gonadal Steroid Hormone Regulation of Proopiomelanocortin Gene Expression in Arcuate Neurons That Innervate the Medial Preoptic Area of the Rat

The density of beta-endorphin (beta-endo)-like immunoreactive (IR) fibers in the medial preoptic area (MPOA) has been shown to vary across the estrous cycle and is gonadal steroid hormone-dependent. These beta-endo-containing fibers are presumably projections of proopiomelanocortin (POMC) neurons which are located in the arcuate nucleus (ARC). POMC mRNA level varies across the estrous cycle in the ARC and its expression is differentially altered by gonadal steroid hormones. However, it is unclear how gonadal steroids regulate POMC gene expression in ARC neurons that innervate the MPOA. Therefore, combined fluorogold (FG) retrograde neuronal labeling and in situ hybridization histochemistry were used to investigate the effects of gonadal steroid hormone treatment on POMC gene expression in ARC neurons supplying the MPOA of ovariectomized (OVX) female rats. POMC-expressing cells were located in the ARC and median eminence (ME), wherein such neurons were significantly larger than unlabeled cells that surround them. A relatively greater number of ARC POMC neurons were observed to innervate the medial portion of the medial preoptic nucleus (MPN) than the lateral portion of the MPN. Estradiol (E2) and progesterone (P) treatment before FG injection did not affect the number of FG and POMC double-labeled neurons in the ARC, which suggests that hormone treatment did not alter the number of POMC-expressing neurons projecting to the MPN. In OVX animals, ARC POMC mRNA labeling was relatively low, and increased significantly in neurons of the most rostral ARC region 48 h after E2 treatment. P administration enhanced and prolonged the effect of E2 in this group of ARC neurons. E2P treatment significantly increased POMC mRNA expression beginning 13 h after P injection in all but the most caudal ARC POMC neurons. Thereafter, E2P treatment gradually increased POMC mRNA expression for at least 1 additional day. Gonadal steroid hormone treatment apparently affects POMC mRNA expression uniformly in neurons of the same ARC subdivision without regard to their efferent targets. Diurnal variation of POMC mRNA expression is present only in the most rostral ARC region, which contains a population of E2-sensitive POMC neurons. The results suggest that the relatively greater beta-endo-like IR fiber density in the medial MPN is due to a greater number of POMC neurons innervating this region. The pattern of innervation of the MPN by POMC neurons is unaffected by gonadal steroid hormone treatment, which appears to induce POMC expression in ARC neurons, and eventually to stimulate the synthesis and transport of beta-endo in POMC neuronal axons which project to the MPOA.(ABSTRACT TRUNCATED AT 400 WORDS)

The sympathetic and parasympathetic nature of neuropeptide Y-immunoreactive nerve fibres in the major salivary glands of the rat

The distribution and origin of neuropeptide Y in the major salivary glands of the rat was studied by indirect immunofluorescence technique. Numerous nerve fibres immunoreactive for the peptide were seen in the parotid and sublingual glands. Most of the fibres were located around blood vessels and salivary acini. In the submandibular gland the number of immunoreactive nerve fibres around the acini was lower in comparison with that in the parotid and sublingual glands. Some immunoreactive nerve fibres were also found around or along intra- and interlobular ducts in all major salivary glands. A large number of the neuropeptide-containing neuronal cell bodies and nerve fibres were detected in the sympathetic superior cervical ganglion. Sympathetic postganglionic nerve trunks of this ganglion contained numerous immunoreactive nerve fibres as well. A subpopulation of the neuronal cell bodies in the submandibular ganglion were immunoreactive to neuropeptide Y. Both uni- and bilateral superior cervical ganglionectomies caused a significant decrease in the number of immunoreactive nerve fibres around the blood vessels in all the major salivary glands. However, these denervations did not affect the density of nerve fibres around the acini and ducts. On the contrary, unilateral parasympathetic denervation by sectioning the auriculotemporal nerve reduced the fibres around the secretory acini in the parotid gland remarkably, while only a minor reduction in the density of immunoreactive fibres associated with the blood vessels of the gland was detected. Unilateral electrocoagulation of the trigeminal nerve branches caused no detectable change in the density of immunoreactive nerve fibres in any of the major salivary glands.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of dynorphin A (1-17) in the cat brainstem: an immunocytochemical study.

We have studied the distribution of cell bodies and fibers containing dynorphin A (1-17) in the brainstem of the cat using an indirect immunoperoxidase technique. The highest density of cell bodies was observed in the nucleus of the trapezoid body, whereas a low density of perikarya was found in the inferior and superior colliculi, nucleus of the brachium of the inferior colliculus and in the alaminar and laminar spinal trigeminal nuclei. A moderate density of immunoreactive fibers was found in the nucleus of the solitary tract, dorsal nucleus of the raphe, area postrema, dorsal motor nucleus of the vagus and in the marginal nucleus of the brachium conjunctivum, whereas a low density of fibers was observed in the lateral tegmental field, laminar and alaminar spinal trigeminal nuclei, nucleus of the trapezoid body, nucleus coeruleus, brachium conjunctivum, Kölliker-Fuse nucleus, periaqueductal gray and in the inferior and superior colliculi. The highest density of fibers containing dynorphin A was visualized in the substatia nigra. The widespread distribution of dynorphin A (1-17) immunoreactive structures suggests that the peptide could be involved in respiratory, cardiovascular, nociceptive and auditory mechanisms.

Distribution of gastrin-releasing peptide/bombesin-like immunoreactive cell bodies and fibres in the brainstem of the cat

Using an indirect immunoperoxidase technique, the location of gastrin-releasing/bombesin-like immunoreactive fibres and cell bodies in the cat brainstem was studied. A moderate or low density of immunoreactive cell bodies was observed in the nucleus of the brachium of the inferior colliculus, pericentral nucleus of the inferior colliculus, ventral nucleus of the lateral lemniscus and in the external division of the lateral reticular nucleus. The densest network of immunoreactive fibres was visualized in the interpeduncular nucleus, marginal nucleus of the brachium conjunctivum, alaminar and laminar spinal trigeminal nuclei and in the substantia nigra. The periaqueductal gray, brachium of the inferior colliculus, nucleus of the brachium of the inferior colliculus, locus coeruleus, nucleus incretus, Kölliker-Fuse nucleus, facial nucleus, medial nucleus of the solitary tract and the area postrema contained a moderate density of immunoreactive fibres, whereas the pericentral nucleus of the inferior colliculus, nucleus sagulum, cuneiform nucleus, dorsal nucleus of the raphe, superior central nucleus, central, lateral and paralemniscal tegmental fields, ventral nucleus of the lateral lemniscus, dorsal tegmental nucleus, postpyramidal nucleus of the raphe, nucleus ambiguus, accessory dorsal tegmental nucleus, dorsal motor nucleus of the vagus and the inferior olive had the lowest density of immunoreactive fibres.

Galanin-like immunoreactivity in the cat brainstem.

The distribution of galanin-like immunoreactive fibers and cell bodies has been studied in the cat brainstem. Perikarya containing galanin were only found, at a low density, in the nucleus of the brachium of the inferior colliculus and in the pericentral nucleus of the inferior colliculus. The highest density of immunoreactive fibers was found in the laminar spinal trigeminal nucleus and in the parvocellular division of the alaminar spinal trigeminal nucleus. A moderate density of immunoreactive fibers was observed in the periaqueductal gray, locus coeruleus, marginal nucleus of the brachium conjunctivum and below the facial nucleus, whereas a low density of such fibers was found in the nucleus of the brachium of the inferior colliculus, pericentral nucleus of the inferior colliculus, nucleus incertus, medial division of the dorsal nucleus of the raphe, accessory dorsal tegmental nucleus, Kölliker-Fuse nucleus, lateral tegmental field, postpyramidal nucleus of the raphe, pericentral division of the dorsal tegmental nucleus, infratrigeminal nucleus, medial nucleus of the solitary tract, spinal trigeminal tract, dorsal motor nucleus of the vagus, and in the lateral reticular nucleus. According to the distribution of galanin-like immunoreactive structures in the cat brainstem, our data suggest that the peptide could be involved in respiratory, cardiovascular, nociceptive and auditory mechanisms.

Distribution of gastrin-releasing peptide/bombesin-like immunoreactivity in the rainbow trout brain

The distribution of gastrin-releasing peptide(14–27)/bombesin-like immunoreactivity was studied in the brain of the teleost Oncorhynchus mykiss using an indirect immunoperoxidase technique. Cell bodies were only found in the hypothalamic nuclei posterioris periventricularis, the anterior part of the recessus lateralis, and in the recessus posterioris. Immunoreactive fibers were widely distributed in the diencephalon, midbrain, and hindbrain. The highest density of immunoreactive fibers was found in the hypothalamus, whereas a moderate to low density of fibers was visualized in the periventricular thalamus. In the midbrain, a moderate density of fibers was observed at the level of the nuclei lateralis and centralis of the torus semicircularis, the stratum album centrale of the optic tectum, the nucleus of the rostral mesencephalic tegmentum, the nuclei lateralis valvulae, the lemnisci lateralis, istmi and locus coeruleus, as well as in the hindbrain at the level of the nuclei gustatorius secundarius, cerebelli, descendens nervi trigemini, and funiculi lateralis. These data suggest that the peptide could be involved in neuroendocrine (LT, nRL, nRP), visual (OT, nRTM, TS, Is), auditory (TS), and nociceptive (Vd, nufl) mechanisms.

Alpha-neo-endorphin-like immunoreactivity in the cat brain stem

This paper examines the distribution of fibers and cell bodies containing alpha-neo-endorphin in the cat brain stem by using an indirect immunoperoxidase technique. A high or moderate density of immunoreactive cell bodies was found in the superior central nucleus, nucleus incertus, dorsal tegmental nucleus, nucleus of the trapezoid body, and in the laminar spinal trigeminal nucleus, whereas a low density of such perikarya was observed in the inferior colliculus, nucleus praepositus hypoglossi, dorsal nucleus of the raphe, nucleus of the brachium of the inferior colliculus, and in the nucleus of the solitary tract. The highest density of immunoreactive fibers was found in the substantia nigra, dorsal motor nucleus of the vagus, nucleus coeruleus, lateral tegmental field, marginal nucleus of the brachium conjunctivum, and in the inferior and medial vestibular nuclei. These results indicate that alpha-neo-endorphin is widely distributed in the cat brain stem and suggest that the peptide could play an important role in several physiological functions, e.g., those involved in respiratory, cardiovascular, auditory, and motor mechanisms.

Neuropeptide Y in the carp torus semicircularis: an immunocytochemical study.

The presence of neuropeptide Y-like immunoreactivity in the torus semicircularis of the teleost fish Cyprinus carpio was studied using an indirect immunoperoxidase technique. In general, both the nuclei lateralis and centralis of the torus semicircularis showed a high density of immunoreactive fibers from rostral to caudal levels. In particular, in the nucleus lateralis a low density of immunoreactive fibers was only found in the subependymal layer, whereas this was high in the small cell, fibrillar and disperse cells layers. Similarly, the nucleus centralis showed a low density of immunoreactive fibers in the fibrillar cortex, and a high density in the cellular region. Moreover, a moderate density of fusiform or round-ovoid cell bodies containing neuropeptide Y-like immunoreactivity was found in the cellular region of the nucleus centralis. These neurons were located dorsally or near to the lateral lemniscus, and situated perpendicular, parallel or oblique to the surface, showing one or two long and relatively unbranching dendritic trunks. The localization of neuropeptide Y-like immunoreactivity in both nuclei--lateralis and centralis--of the carp torus semicircularis suggests that this peptide is involved in the control of visual, auditive, and lateral line mechanisms, as well as in the control of feeding.

Neurokinin A-like immunoreactivity in the cat brainstem

We have studied the distribution of neurokinin A-like immunoreactive cell bodies and fibers in the cat brainstem. The densest clusters of perikarya containing the peptide were observed in the periaqueductal gray, inferior colliculus, postpyramidal nucleus of the raphe, medial nucleus of the solitary tract and in the lateral reticular nucleus. By contrast, the interpeduncular nucleus, magnocellular part of the red nucleus, central tegmental field, cuneiform nucleus, dorsal tegmental nucleus, nucleus sagulum and the medial and inferior vestibular nuclei had the lowest density, whereas a moderate density of immunoreactive cell bodies was found in the superior colliculus, medial division of the dorsal nucleus of the raphe, nucleus incertus, locus coeruleus and in the Kölliker-Fuse area. The highest density of immunoreactive fibers was observed in the substantia nigra, periaqueductal gray, marginal nucleus of the brachium conjunctivum, medial vestibular nucleus, medial nucleus of the solitary tract, laminar spinal trigeminal nucleus, inferior colliculus, medial division of the dorsal nucleus of the raphe, locus coeruleus, dorsal tegmental nucleus and in the spinal trigeminal tract. A moderate density of immunoreactive fibers was found in the dorsal motor nucleus of the vagus and in the postpyramidal nucleus of the raphe and a low density in the cuneiform nucleus, Kölliker-Fuse area, nucleus sagulum, inferior and superior central nuclei, lateral reticular nucleus and in the lateral and magnocellular tegmental fields.

Distribution of secretoneurin, a peptide derived from secretogranin II, in rat brain: An immunocytochemical and radioimmunological study

The distribution of secretoneurin, a peptide derived from its precursor secretogranin II by proteolytic processing, was studied in the central nervous system of the rat by immunocytochemistry and radioimmunoassay and compared to the distribution of secretogranin II messenger RNA by using in situ hybridization. With a specific antiserum a distinct staining of fibers and to a lesser extent also of perikarya was observed throughout the central nervous system. A high density of immunoreactive fibers and terminals was found in several brain areas, i.e. the lateral septum, the medial parts of the amygdala, some medial thalamic nuclei, the hypothalamus, habenula, nucleus interpeduncularis, locus coeruleus, nucleus tractus solitarii, the substantiae gelatinosae of the caudal trigeminal nucleus and of the spinal cord. The quantitative distribution as measured by a radioimmunoassay agreed well with the varying densities of immunoreactivity found by immunocytochemistry. The highest concentrations of this peptide were present in the hypothalamus, in particular, in the median eminence and are comparable to those of the most highly concentrated neuropeptides. The distribution of immunopositive perikarya corresponded well with that of secretogranin II messenger RNA obtained by in situ hybridization. The pattern of secretoneurin expression in rat brain was widespread and unique, partially overlapping with established chemical transmitters and neuropeptides. The functional significance of this new brain peptide remains to be established.

Distribution of neurokinin A in the cat diencephalon: An immunocytochemical study

The distribution of neurokinin A-like immunoreactive cell bodies and fibers in the diencephalon of the cat was studied using an indirect immunoperoxidase technique. A high or moderate density of immunoreactive neurons was observed in the nuclei habenularis lateralis, median's dorsalis, parafascicularis, hypothalamus posterior, area hypothalamica dorsalis, hypothalamus lateralis, periventricularis hypothalami, above the corpus mamillare, and in the perifornical area, whereas scarce immunoreactive perikarya were visualized in the nuclei reuniens, hypothalami ventromedialis, hypothalamus dorsomedialis, and mamillaris lateralis. The highest density of fibers containing neurokinin A was found in the nuclei periventricularis anterior, rhomboidens, centralis medialis, periventricularis hypothalami, and supraopticus. In the regio praeoptica, area hypothalamica dorsalis, hypothalamus posterior, and in the perifornical area a moderate density of immunoreactive fibers was observed, whereas the nuclei habenularis lateralis, medialis dorsalis, mamillaris lateralis, parataenialis, reuniens, habenularis medialis, filiformis, hypothalamus dorsomedialis, hypothalami ventromedialis, arcuatus, and suprachiasmaticus showed a low density of neurokinin A immunoreactive fibers.

Effect of changes in the intrahippocampal vasopressin on memory retrieval and relearning

Previous results have indicated the involvement of the hippocampus in the behavioral effect of vasopressin, with a better effect when the peptide was injected in the ventral part rather than in the dorsal part of this structure. The purpose of the present study was to determine, in mice, whether the injection of vasopressin or vasopressin antisera into the ventral hippocampus has an effect on retrieval and relearning of a Go-No Go visual discrimination task and, if so, to what extent this involvement of the vasopressin system depends on the integrity of the medial amygdaloid nucleus, the main source of vasopressin innervation in the ventral hippocampus in rats. In the first experiment, we showed that pretest microinjection of Arg8-vasopressin (25 pg per animal) in the ventral hippocampus alleviated forgetting observed after a prolonged interval of 24 days between the acquisition of information and its retrieval. This enhancing effect was characterized by better retrieval and relearning in vasopressin-treated mice than those in control mice. Conversely, an immunoneutralization of endogenous vasopressin in the ventral hippocampus by the microinjection of vasopressin antisera (1/10 dilution) resulted in the drastic impairment of retrieval and relearning. Since the lack of an observable change in a locomotor activity test might explain these results, we postulated that the vasopressin system in the ventral hippocampus is involved in retrieval processes. Moreover, the effects of these treatments in a nonassociative context suggest that the effect of vasopressin could be dependent on the contextual paradigm used. In the second experiment, we localized vasopressin immunoreactive fibers in the CA1-CA2 ventral hippocampal fields and CA4-gyrus dentatus region, and vasopressin perikarya in the medial amygdaloid nucleus. Then, the projection of vasopressin cells from the medial amygdaloid nucleus to the ventral hippocampus was evaluated by studying changes in vasopressin immunoreactive fiber density in the ventral hippocampus after a lesion of the medial amygdaloid nucleus. The results showed the almost complete disappearance of vasopressin fibers in the CA1-CA2 hippocampal fields after the medial amygdaloid lesion. In contrast, vasopressin fibers in the CA4 and gyrus dentatus region remain unchanged. On the basis of our immunohistochemical results, our third experiment tested the repercussions of the change in vasopressin innervation in the ventral hippocampus, due to the medial amygdaloid lesion, on the effects of exogenously administered vasopressin on both retrieval and relearning processes. The medial amygdaloid lesion induced a deleterious effect on retrieval without really affecting the ability to relearn. No observable change in locomotor activity could explain this impairment.(ABSTRACT TRUNCATED AT 400 WORDS)

Distribution of corticotropin-releasing hormone immunoreactivity in golden hamster brain

The distribution of corticotropin-releasing hormone-immunoreactive (CRH-IR) neurons and fibers was observed in golden hamsters. CRH-IR neurons and fibers were observed within the hypothalamus, thalamus, amygdala, cortex, midbrain, and hindbrain. The largest numbers of CRH-IR neurons were seen within the magnoand parvocellular divisions of the paraventricular nucleus of the hypothalamus and within the septum, bed nucleus of the stria terminalis, preoptic area continuum. The highest density of immunoreactive fibers was observed in the external zone of the median eminence. In addition, many immunoreactive fibers were observed within the bed nucleus of the stria terminalis and the preoptic area. The distribution obtained in hamsters was compared with previously reported distributions from rats, and both were generally similar.