Showing papers on "Hypothalamus published in 1990"

Transplanted suprachiasmatic nucleus determines circadian period

Abstract: The pacemaker role of the suprachiasmatic nucleus in a mammalian circadian system was tested by neural transplantation by using a mutant strain of hamster that shows a short circadian period. Small neural grafts from the suprachiasmatic region restored circadian rhythms to arrhythmic animals whose own nucleus had been ablated. The restored rhythms always exhibited the period of the donor genotype regardless of the direction of the transplant or genotype of the host. The basic period of the overt circadian rhythm therefore is determined by cells of the suprachiasmatic region.

Expression of C-fos-like protein as a marker for neuronal activity following noxious stimulation in the rat

Abstract: C-fos is a proto-oncogene that is expressed within some neurons following depolarization. The protein product, c-fos protein, can be identified by immunohistochemical techniques. Therefore, c-fos expression might be used as a marker for neuronal activity throughout the neuraxis following peripheral stimulation. This study has analyzed patterns of c-fos expression in both control and anesthetized animals and in anesthetized rats subjected to various forms of peripheral stimulation. Labeled cells were counted in the spinal cord, brainstem, hypothalamus, and thalamus. Little c-fos immunoreactivity was found in control animals. Prolonged inhalational anesthesia increased the number of labeled cells at several brainstem sites. Noxious stimulation of anesthetized rats induced c-fos within the neuraxis in patterns consistent with data obtained from electrophysiological studies and in additional locations for which few direct electrophysiological data are available, such as the ventrolateral medulla, the posterior hypothalamic nucleus, and the reuniens and paraventricular thalamic nuclei. Gentle mechanical stimulation was ineffective in inducing c-fos-like protein. The data suggest that c-fos can be used as a transynaptic marker for neuronal activity following noxious stimulation. However, c-fos is expressed only in some kinds of neurons following peripheral stimulation, and it therefore may be an incomplete marker for nociresponsive activity. In addition, at least a few neurons express c-fos protein in the absence of noxious stimulation. Experiments analyzing c-fos expression must be designed with care, as both extraneous stimuli and anesthetic depth influence the results.

Increased hypothalamic content of preproneuropeptide Y messenger ribonucleic acid in genetically obese Zucker rats and its regulation by food deprivation.

Abstract: Neuropeptide Y (NPY) is a potent orexigenic agent capable of producing hyperphagia and obesity. NPY-containing neurons project from the hypothalmic arcuate nucleus to the paraventricular nucleus, an area known to be sensitive to the orexigenic effects of NPY. In this study we investigated the possibility that preproNPY messenger RNA (mRNA) content may be altered in obese Zucker rats compared to that of their lean littermates. Total RNA was isolated from hypothalamic dissections from male and female, obese and lean Zucker rats. RNA was also isolated from dissections of: olfactory bulb, entorhinal cortex, hippocampus, and striatum of female obese and lean rats. PreproNPY mRNA content was determined by solution hybridization-RNase protection analysis. The results revealed a 2- to 3-fold increase in preproNPY mRNA levels in the hypothalamus of obese animals compared to lean. The increase was observed in both sexes and was specific to the hypothalamus. In situ hybridization localized this increase to the arcuate nucleus. An additional RNase protection study was pursued to investigate the effects of 72 h food deprivation on hypothalamic preproNPY mRNA levels in lean and obese animals. Lean animals displayed an approximate 2-fold increase in preproNPY mRNA content, whereas obese animals showed no significant increase after food deprivation. These data are consistent with the hypothesis that NPY projections within the hypothalamus are involved in regulating feeding behavior and weight gain, and that disturbed regulation of hypothalamic NPY expression may play a role in the etiology of obesity in the genetically obese Zucker rat.

Organization of adrenergic inputs to the paraventricular and supraoptic nuclei of the hypothalamus in the rat.

Abstract: Anterograde transport, retrograde transport, and immunohistochemical techniques were used to characterize the organization of neural inputs to the paraventricular (PVH) and supraoptic (SO) nuclei from the C1, C2, and C3 adrenergic cell groups in the rostral medulla. The results are as follows: 1) Phenylethanolamine-N-methyltransferase-immunoreactive (PNMT-IR) fibers and terminals were distributed to all parts of the parvicellular division of the PVH; the dorsal and dorsal medial subdivisions received the most prominent inputs, the lateral and ventral medial parts the least. Sparse terminal fields were found consistently in the magnocellular division of the PVH and in the SO. 2) A combined retrograde transport-immunohistochemical method was used to estimate the number and proportion of cells in the regions of the C1, C2, and C3 cell groups that contribute to the PNMT-IR innervation of the PVH. On average, 232 +/- 37 retrogradely labeled cells in the C1 cell group, 73 +/- 32 in the C2 cell group, and 96 +/- 26 in the C3 group stained positively for PNMT-IR. These values comprised 70%, 84%, and 89%, respectively, of all retrogradely labeled neurons in these regions. 3) Fibers and terminals arising from the regions of each of the three adrenergic cell groups were labeled by local injections of the anterogradely transported plant lectin PHA-L. Each component projection was found to distribute in a very similar fashion and to mimic the overall distribution of PNMT-IR; differential projection patterns within the PVH or SO were not seen consistently following deposits in any of the individual adrenergic cell groups or at different rostrocaudal levels of any individual cell group. 4) A dual anterograde tracing (PHA-L)-immunohistochemical (PNMT) labeling method revealed an appreciable number of varicosities arising from the regions of C1, C2, and C3 cell groups to contain PNMT-IR. These results suggest that adrenergic inputs to the PVH and SO, while arising from distinct medullary cell groups and presumably relaying different types of sensory information, are in a position to influence similar groups of parvicellular neurosecretory and/or autonomic-related projection neurons.

Endothelin: A novel peptide in the posterior pituitary system

Abstract: Endothelin (ET), originally characterized as a 21-residue vasoconstrictor peptide from endothelial cells, is present in the porcine spinal cord and may act as a neuropeptide. Endothelin-like immunoreactivity has now been demonstrated by immunohistochemistry in the paraventricular and supraoptic nuclear neurons and their terminals in the posterior pituitary of the pig and the rat. The presence of ET in the porcine hypothalamus was confirmed by reversed-phase high-pressure liquid chromatography and radioimmunoassay. Moreover, in situ hybridization demonstrated ET messenger RNA in porcine paraventricular nuclear neurons. Endothelin-like immunoreactive products in the posterior pituitary of the rat were depleted by water deprivation, suggesting a release of ET under physiological conditions. These findings indicate that ET is synthesized in the posterior pituitary system and may be involved in neurosecretory functions.

Comparative distribution of neuropeptide-immunoreactive systems in the brain of the green molly, Poecilia latipinna.

Abstract: The comparative distribution of peptidergic neural systems in the brain of the euryhaline, viviparous teleost Poecilia latipinna (green molly) was examined by immunohistochemistry. Topographically distinct, but often overlapping, systems of neurons and fibres displaying immunoreactivity (ir) related to a range of neuropeptides were found in most brain areas. Neurosecretory and hypophysiotrophic hormones were localized to specific groups of neurons mostly within the preoptic and tuberal hypothalamus, giving fibre projections to the neurohypophysis, ventral telencephalon, thalamus, and brain stem. Separate vasotocin (AVT)-ir and isotocin (IST)-ir cells were located in the nucleus preopticus (nPO), but many AVT-ir nPO neurons also displayed growth hormone-releasing factor (GRF)-like-ir, and in some animals corticotrophin-releasing factor (CRF)-like-ir. The main group of CRF-ir neurons was located in the nucleus recessus anterioris, where coexistence with galanin (GAL) was observed in some cells. Enkephalin (ENK)-like-ir was occasionally present in a few IST-ir cells of the nPO and was also found in small neurons in the posterior tuberal hypothalamus and in a cluster of large cells in the dorsal midbrain tegmentum. Thyrotrophin-releasing hormone (TRH)-ir cells were found near the rostromedial tip of the nucleus recessus lateralis. Gonadotrophin-releasing hormone (GnRH)-ir cells were present in the nucleus olfactoretinalis, ventral telencephalon, preoptic area, and dorsal midbrain tegmentum. Molluscan cardioexcitatory peptide (FMRF-amide)-ir was colocalized with GnRH-ir in the ganglion cells and central projections of the nervus terminalis. Melanin-concentrating hormone (MCH)-ir neurons were restricted to the tuberal hypothalamus, mostly within the nucleus lateralis tuberis pars lateralis, and somatostatin (SRIF)-ir neurons were numerous throughout the periventricular areas of the diencephalon. A further group of SRIF-ir neurons extending from the ventral telencephalon into the dorsal telencephalon pars centralis also contained neuropeptide Y (NPY)-, peptide YY (PYY)-, and NPY flanking peptide (PSW)-like-ir. These immunoreactivities were, however, also observed in non-SRIF-ir cells and fibres, particularly in the mesencephalon. Calcitonin gene-related peptide (CGRP)-like-ir had a characteristic distribution in cells grouped in the isthmal region and fibre tracts running forward into the hypothalamus, most strikingly into the inferior lobes. Antisera to cholecystokinin (CCK) and neurokinin A (NK) or substance P (SP) stained very extensive, separate systems throughout the brain, with cells most consistently seen in the ventral telencephalon and periventricular hypothalamus. Broadly similar, but much more restricted, distributions of cells and fibres were seen with antisera to neurotensin (NT) and vasoactive intestinal peptide (VIP).(ABSTRACT TRUNCATED AT 400 WORDS)

Luteinizing hormone-releasing hormone neurons express Fos protein during the proestrous surge of luteinizing hormone.

Abstract: The ability of luteinizing hormone-releasing hormone (LHRH) neurons to express the oncogene c-fos was examined during the estrous cycle in rats. The immunocytochemical localization of the c-fos-encoded antigen, Fos, was coupled with the immunocytochemical localization of LHRH. LHRH neurons showed no Fos immunoreactivity during diestrus-1, diestrus-2, estrus, or the morning of proestrus. However, Fos was expressed in LHRH neurons from 1600 to 2200 hours during proestrus. The timing of onset of Fos expression in LHRH neurons during proestrus suggests a strong correlation with increased LH secretion. Pentobarbital, which blocks the preovulatory LH surge, blocked Fos expression in LHRH neurons, but the LHRH neurons expressed Fos on the following afternoon at the time of the expected delayed LH surge. Not all LHRH neurons expressed Fos during the LHRH surge. Approximately half of the LHRH neurons were activated in the preoptic area and anterior hypothalamus; more anteriorly positioned LHRH neurons did not express Fos, resulting in an overall stimulation of 40% of the LHRH neurons. These data provide direct evidence that stimulation of LHRH neurons during proestrus takes place at the LHRH cell bodies, and identify the specific population of LHRH neurons which are activated.

Serotonin and Appetite

Abstract: Feeding or food withdrawal can affect the supply of tryptophan to the brain and hence (in some circumstances) 5-HT synthesis therein. Also fenfluramine which releases 5-HT to postsynaptic receptors suppresses appetite, and there are reports that tryptophan can have a similar effect. Furthermore, feeding is reported to release hypothalamic 5-HT. Therefore 5-HT could have a role in the normal termination of feeding and perhaps also in disorders of appetite. The recognition of various 5-HT receptor subtypes has stimulated research in this area. We have now investigated the involvement of the subtypes in the pharmacological control of feeding. Thus, 5-HT1A agonists (8-OHDPAT, buspirone, gepirone, etc.) stimulate intake in freely feeding rats, probably by activating autoreceptors on the cell bodies of 5-HT neurons so that 5-HT release at terminals is decreased. The hyperphagia is not explicable by increased activity or gnawing and is strikingly manifest against carbohydrate in carbohydrate vs. protein choice experiments. Feeding in previously food-deprived rats is decreased by the 5-HT agonists RU 24969, 1-(3-chlorophenyl) piperazine (mCPP) and 1-(3-trifluoromethyl) phenyl) piperazine (TFMPP). Effects of antagonists on these properties suggest that RU 24969-induced hypophagia depends on 5-HT1B receptors only, while mCPP and TFMPP induce hypophagia at 5-HT1C sites, though this effect also requires 5-HT1B receptors for its expression. Responsible sites occur in the paraventricular nucleus of the hypothalamus as infusing either RU 24969 or TFMPP therein causes hypophagia. On systemic injection, the hypophagic drugs are particularly active in female rats, an effect of conceivable relevance to human anorexic illness.

Immunohistochemical demonstration of a novel hypothalamic peptide, pituitary adenylate cyclase-activating polypeptide, in the ovine hypothalamus.

Abstract: We recently reported isolation, characterization and synthesis of a novel ovine hypothalamic peptide with 38 residues which stimulates accumulation of cAMP in rat anterior pituitary cell cultures. The peptide was named PACAP38 (pituitary adenylate cyclase-activating polypeptide with 38 residues). The presence of another peptide corresponding to the N-terminal 1-27 residues (PACAP27) was also demonstrated. Both PACAP38 and PACAP27 have an amidated C-terminus. Antisera against synthetic PACAP27 were generated in rabbits. These antisera were tested for titer and specificity in enzyme-linked immunosorbent assay. One of the antisera (no. 88121-3) exhibited a high titer of antibody, which was specific to PACAP27 and PACAP38 with exception of slight cross-reactivity with ovine CRF (oCRF). Therefore, the antibodies against oCRF were removed from the antiserum using a solid phase method. Removal of oCRF antibodies was confirmed by enzyme-linked immunosorbent assay. A dense immunoreactive fiber network was found in both external and internal zones of the median eminence and pituitary stalk. The fibers were demonstrated to be in close contact with the hypophysial portal capillaries. The preabsorption of antiserum with vasoactive intestinal polypeptide or with the mixture containing TRH, LHRH, oCRF, ovine GH-releasing factor, somatostatin, and bovine thyroglobulin did not affect the immunostaining. On the other hand, the preabsorption of antiserum with an excess of PACAP27 or PACAP38 abolished the immunostaining. Therefore, the staining is considered specific for PACAP27 and PACAP38. Stained fibers were also present in the posterior pituitary. A dense fiber network was observed and the lateral hypothalamus the fibers appeared to cling to unstained neuronal cell bodies and their dendrites. In the lateral septum the fibers surrounded some blood vessels. Immunolabeled cell bodies were found in the paraventricular and supraoptic nuclei. These findings support the view that PACAP may play a multifunctional role, including that of a hypophysiotropic hormone, neurotransmitter, neuromodulator, and vasoregulator.

Gonadal Steroids Modify Dendritic Spine Density in Ventromedial Hypothalamic Neurons: A Golgi Study in the Adult Rat

Abstract: Neurons in the adult rat ventromedial hypothalamic nucleus (VMN, 4–6 neurons per brain; 3–7 brains per group) were studied under various hormonal conditions using the single-section Golgi impregnation

Chemical characterization of neuroendocrine targets for progesterone in the female rat brain and pituitary.

Abstract: The secretory products of some of the cell types which respond directly to actions of progesterone in the female rat brain and pituitary were determined by combining immunocytochemistiy with autoradio

Behavioral effects of progesterone associated with rapid modulation of oxytocin receptors

Abstract: The ventromedial nuclei of the hypothalamus (VMN) are important for the control of feminine mating behavior, and hormone action within these nuclei has been causally related to behavior. Estradiol induces receptors for oxytocin in the VMN and in the area lateral to these nuclei over the course of 1 to 2 days, and progesterone causes, within 30 minutes of its application, a further increase in receptor binding and an expansion of the area covered by these receptors lateral to the VMN. The rapid progesterone effect appears to be a direct and specific effect of this steroid on the receptor or membrane, because it was produced in vitro as well as in vivo and was not mimicked by a variety of other steroids. The effect of progesterone occurred in the posterior part of the VMN, where oxytocin infusion facilitated feminine mating behavior; it did not take place in the anterior part of the VMN, where oxytocin infusion had no effect on mating behavior.

Expression of the potent vasoconstrictor endothelin in the human central nervous system.

Abstract: Endothelin is a potent vasoconstrictive peptide initially characterized as a product of endothelial cells. To examine the potential role of endothelin as a neuropeptide, we studied its distribution in the human central nervous system. RNA blot hybridization provided evidence of endothelin gene transcription in a variety of functional regions of the brain. In situ hybridization confirmed the widespread pattern of endothelin transcription and indicated that the highest density of cells containing endothelin mRNA is in the hypothalamus. This technique localized endothelin transcription to cells of the nervous system as well as the vascular endothelium. Immunocytochemical studies detected endothelin immunoreactivity in neurons, providing evidence of the synthesis of the peptide in this cell type and confirming that endothelin is a neuropeptide. Although the prominent expression of endothelin in the hypothalamus may indicate a central vasoregulatory role for the peptide, the widespread distribution of endothelin in neurons in other areas of the brain implies a more fundamental role in the regulation of nervous system function.

Expression cloning of a cDNA encoding the mouse pituitary thyrotropin-releasing hormone receptor.

Abstract: Thyrotropin-releasing hormone (TRH) is an important extracellular regulatory molecule that functions as a releasing factor in the anterior pituitary gland and as a neurotransmitter/neuromodulator in the central and peripheral nervous systems Binding sites for TRH are present in these tissues, but the TRH receptor (TRH-R) has not been purified from any source Using Xenopus laevis oocytes in an expression cloning strategy, we have isolated a cDNA clone that encodes the mouse pituitary TRH-R This conclusion is based on the following evidence Injection of sense RNA transcribed in vitro from this cDNA into Xenopus oocytes leads to expression of cell-surface receptors that bind TRH and the competitive antagonist chlordiazepoxide with appropriate affinities and that elicit electrophysiological responses to TRH with the appropriate concentration dependency Antisense RNA inhibits the TRH response in Xenopus oocytes injected with RNA isolated from normal rat anterior pituitary glands Finally, transfection of COS-1 cells with this cDNA leads to expression of receptors that bind TRH and chlordiazepoxide with appropriate affinities and that transduce TRH stimulation of inositol phosphate formation The 38-kilobase mouse TRH-R cDNA encodes a protein of 393 amino acids that shows similarities to other guanine nucleotide-binding regulatory protein-coupled receptors

Tumor Necrosis Factor a Inhibits the Hormonal Response of the Pituitary Gland to Hypothalamic Releasing Factors

Abstract: Tumor necrosis factor α (TNFα), a monokine produced by activated macrophages and monocytes, may be an essential mediator of the pathogenesis and of the hormonal response to endotoxic shock. It has been suggested that an elevated level of TNFα is a marker for morbidity and mortality during septic shock, and that treatment with antibodies against TNFα decreases mortality. Because monokines have been shown to interact at the hypothalamic-pituitary level, we have studied the effect of TNFα on basal and stimulated hormone release from normal rat anterior pituitary cells. After 3 days of incubation, primary cultures of rat anterior pituitary cells were stimulated with either 0.5 ng/ml CRF, 3 ng/ml AVP, 10 ng/ml angiotensin II (All), 10-6 M TRF, 10-8 M LHRH, or 10-8 M GHRH, alone or in the presence of 20 or 50 ng/ml human or murine recombinant TNFα. The culture media were analyzed for ACTH, GH, LH, and PRL content. Each experiment was performed in triplicate and was repeated 3 to 8 times. Timecourse experiments ...

Anatomical substrates of cholinergic‐autonomic regulation in the rat

Abstract: Acetylcholine (ACh) plays a major role in central autonomic regulation, including the control of arterial blood pressure (AP) Previously unknown neuroanatomic substrates of cholinergic - autonomic control were mapped in this study Cholinergic perikarya and bouton-like varicosities were localized by an immunocytochemical method empolying a monoclonal antiserum against choline acetyltransferase (ChAT), the enzyme synthesizing ACh In the forebrain, bouton-like varicosities and/or perikarya were detected in the septum, bed nucleus of the stria terminalis, amygdala (in particular, autonomic projection areas AP1 and AP2 bordering the central subnucleus, hypothalamus rostrolateral/innominata transitional area, perifornical, dorsal, incertal, caudolateral, posterior [PHN], subparafascicular, supramammillary and mammillary nuclei Few or no punctate varicosities were labeled in the paraventricular (PVN) or supraoptic (SON) hypothalamic nuclei In the mid and hindbrain, immunoreactive cells and processes were present in the nucleus of Edinger-Westphal, periaqueductal gray, parabrachial complex (PBC), a periceruleal zone avoiding the locus ceruleus (LC), pontine micturition field, pontomedullary raphe, paramedian reticular formation and periventricular gray, A5 area, lateral tegmental field, nucleus tractus solitarii (NTS), nucleus commissuralis, nucleus reticularis rostroventrolateralis (RVL), and the ventral medullary surface (VMS) In the PBC, immunoreactive varicosities identified areas previously unexplored for cholinergic autonomic responsivity superior, internal, dorsal, and central division of the lateral subnucleus, nucleus of Koelliker-Fuse and the medial subnucleus In the NTS, previously undescribed ChAT-immunolabeled cells and processes were concentrated at intermediate and subpostermal levels and distributed viscerotopically in areas receiving primary cardiopulmonary afferents In the nucleus RVL, cholinergic perikarya were in proximity to the VMS and medial to adrenergic cell bodies of the C1 area Punctate varicosities of unknown origin and dendrites extending ventrally from the nucleus ambiguus overlapped the C1 area and immediate surround of RVL In conclusion: 1) Cholinergic perikarya and putative terminal fields, overlap structures that are rich in cholinoreceptors and express autonomic, neuroendocrine, or behavioral responsivity to central cholinergic stimulation (PHN, NTS, RVL) The role of ACh in most immunolabeled areas, however, has yet to be determined Overall, these data support the concept that cholinergic agents act at multiple sites in the CNS and with topographic specificity (2) The absence of immunoreactive elements in the LC, PVN, and SON was unexpected and suggests that cholinergic processing attributed to these nuclei is mediated polysynaptically or by synapses on processes extending into adjacent cholinoreceptor fields (3) Putative cholinergic terminals overlapping sites that relay primary (NTS) or higher-order visceral afferents suggest anatomical substrates for cholinergic regulation of autonomic reflexes (4) ChAT-immunoreactive terminals in areas where cells project to the IML support the view that central cholinergic stimulation provoking sympathoexcitation may be mediated by bulbospinal neurons A rich plexus of varicose fibers overlapping the C7 area of RVL, which provides the excitatory drive for tonic sympathetic discharge, may form the anatomical basis for the increases in sympathetic nerve activity provoked by systemic or central administration of cholinergic agents

Cells of origin of the spinohypothalamic tract in the rat.

Abstract: We recently demonstrated that large numbers of neurons in the spinal cord of rats project directly to the hypothalamus. In the present study, we used the retrograde tracer Fluoro-Gold (FG) to examine this projection more completely. In the first series ofss studies, we attempted to label the entire population of spinal cord neurons that project to the hypothalamus. Injections that virtually filled the hypothalamus on one side without spreading into any other diencephalic area labeled a large number of neurons (estimated to be more than 9,000 in the case with the most neurons labeled) bilaterally at all levels of the spinal cord. Approximately 60° of the labeled neurons were contralateral to the injection. The greatest number of labeled neurons was found within the deep dorsal horn. Many were also found within the lateral spinal nucleus, the superficial dorsal horn, and the gray matter surrounding the central canal. A small number of labeled cells was located in the intermediate zone and ventral horn of the spinal gray matter. Labeled neurons were distributed bilaterally within the sacral parasympathetic nucleus and trigeminal nucleus caudalis. Injections of FG restricted to the medial hypothalamus labeled neurons within the spinal cord in a distribution similar to that produced by injections that filled the hypothalamus. However, fewer neurons were labeled in the spinal cord (estimated to be more than 6,200) and trigeminal nucleus caudalis. Injections of FG restricted to the lateral hypothalamus also labeled fewer neurons (approximately 3,300) than did injections that filled the hypothalamus. In these cases, also, the pattern of labeled neurons within the spinal cord was similar to that produced by injections within either medial or both medial and lateral hypothalamus. However, few neurons were labeled in the sacral parasympathetic nucleus following injections into the lateral hypothalamus. These findings show the distribution of a large number of spinal cord neurons that project directly to medial or lateral hypothalamic regions that are involved in autonomic, neuroendocrine, and emotional responses to somatosensory stimulation, including painful stimuli.

Interleukin-1 stimulates corticotropin-releasing factor gene expression in rat hypothalamus.

Abstract: To examine the effect of interleukin-1 (IL-1) on CRF and POMC gene expression, recombinant human IL-1α and β were ip injected in rats. The plasma ACTH level showed a dose-related increase at 2 h after the injection of 0.5 and 2 μg IL-1α and -β, and also showed a sustained increase from 1 h until 5 h after the injection of 2 μg of IL-1β. CRF contents in the medial basal hypothalamus and ACTH contents in the anterior pituitary (AP) decreased at 2 h after the injection of 2 μg of IL-1α and -β, and such decreased levels were maintained until 5 h after the injection of 2 μg of IL-1β. The levels of CRF mRNA in the hypothalamus and POMC mRNA in AP significantly increased 3 h after the injection of 2 μg IL-1α and β, and these levels were still higher at 5 h after the injection of 2 μg of IL-1β compared with those of the control. There was no significant change in the ACTH content and POMC mRNA levels in the intermediate-posterior pituitary or the hypothalamus or in the CRF contents and CRF mRNA levels in the cere...

Distribution of aromatase in the brain of the Japanese quail, ring dove, and zebra finch: An immunocytochemical study

Abstract: An immunocytochemical peroxidase-antiperoxidase procedure using a purified polyclonal antibody raised against human placental aromatase was used to localize aromatase-containing cells in the brain of three avian species: the Japanese quail, the ring dove, and the zebra finch. In quail and dove, immunoreactive cells were found only in the preoptic area and hypothalamus, with a high density of positive cells being present in the medial preoptic area, in the septal area above the anterior commissure, in the ventromedial nucleus of the hypothalamus, and in rostral part of the infundibulum. Immunoreactivity was weaker in zebra finches, and no signal could therefore be detected in the ventromedial and tuberal hypothalamus. The positive material was localized in the perikarya and in adjacent cytoplasmic processes, including the full length of axons always leaving a clear unstained cell nucleus. These features could be observed in more detail on sections cut from perfused brains and stained with an alkaline phosphatase procedure. The distribution of aromatase immunoreactivity was similar in the three species although minor differences were observed in the preoptic area. The localization of labelled neurons coincided with the distribution of aromatase activity as studied by in vitro radioenzyme assays on brain nuclei dissected by the Palkovits punch method. There was one striking exception to this rule: no immunoreactivity was detected in the zebra finch telencephalon, while assays had shown the presence of an active enzyme in several nuclei such as the robustus archistriatalis, the hyperstriatum ventrale pars caudale, and the hippocampus and area parahippocampalis. The origins of this discrepancy and the functional role of the aromatase observed in the axons are discussed.

Physiological roles of chicken LHRH-I and -II in the control of gonadotrophin release in the domestic chicken.

Abstract: The physiological roles of chicken LHRH-I and -II (cLHRH-I and -II) in the regulation of gonadotrophin release were investigated in the domestic chicken. Measurements of the neuropeptides, using specific radioimmunoassays, in brain sections cut in three planes or in grossly dissected brain areas, showed that cLHRH-II occurs in low amounts throughout the brain whereas cLHRH-I is most abundant in the diencephalon. Within the diencephalon, the largest amount of cLHRH-I occurred in the median eminence of the hypothalamus. The amount of cLHRH-I in the median eminence was higher (P less than 0.05) in laying than in out-of-lay hens. No cLHRH-II was detected in the median eminence in either reproductive state. The amount of cLHRH-I in the hypothalamus was increased (P less than 0.05) in cockerels at the onset of puberty and in somatically immature birds after castration. There were no correlated changes in the amounts of hypothalamic cLHRH-II measured in the same experimental samples. Active immunization of laying hens against cLHRH-I but not against cLHRH-II resulted in the complete regression of the reproductive system and a depression in the concentration of plasma LH. These observations, taken together, suggest that gonadotrophin secretion in the hen is more likely to be directly regulated by cLHRH-I than by cLHRH-II.

Increased Hypothalamic Content of Preproneuropeptide-Y Messenger Ribonucleic Acid in Streptozotocin-Diabetic Rats*

Abstract: Neuropeptide-Y (NPY) is a 36-amino acid C-terminally amidated peptide found within the hypothalamus that can potently stimulate carbohydrate feeding. Moreover, the hypothalamic content of NPY can be modulated by peripheral metabolic status. To further evaluate the regulation of NPY synthesis in states of altered metabolic homeostasis, we measured the hypothalamic content of prepro-NPY mRNA in streptozocin (STZ)-diabetic, STZ-diabetic insulin-replaced, and control rats by both nuclease protection and in situ hybridization analyses. Adult male Sprague-Dawley rats received a single injection of STZ (100 mg/kg, ip) or citric acid (control). Beginning 72 h later one group of STZ-treated animals received daily injections of insulin (4 U Ultralente/day). All animals were killed 17-19 days after STZ or control treatment. STZ-treated animals were hyperglycernic and showed growth failure compared to control rats. Glycemic control was restored by insulin replacement, as was partial growth. Nuclease protection analys...

Peptides and transmitter enzymes in hypothalamic magnocellular neurons after administration of hyperosmotic stimuli: comparison between messenger RNA and peptide/protein levels

Abstract: In situ hybridization histochemistry and indirect immunofluorescence histochemistry were used to study changes in the expression of vasopressin (VP), oxytocin (OXY), tyrosine hydroxylase (TH), galanin (GAL), dynorphin (DYN) and cholecystokinin (CCK) in hypothalamic magnocellular neurons of the paraventricular (PVN) and supraoptic (SON) nuclei of rats. After prolonged administration of 2% sodium chloride as drinking water (salt-loading), the treatment increased the levels of VP, OXY, TH, GAL, DYN and CCK mRNA in the PVN and SON. The increase in CCK mRNA was, however, proportionally higher in the PVN than in the SON. Within cell bodies of the PVN and SON of salt-loaded rats, a depletion of VP- and OXY-like immunoreactivity (LI) and an increase in TH-LI were seen. In salt-loaded/colchicine-treated rats, a marked decrease in GAL- and DYN-LI, but no specific changes in CCK-LI were observed. Within nerve fibers of the posterior pituitary of salt-loaded rats, a marked depletion of VP-, GAL- and DYN-LI was found. Less pronounced depletion was observed in OXY- and CCK-LI, and no specific changes in TH-LI were seen. The results show that high plasma osmolality induces increased mRNA levels for VP, OXY, TH, GAL, DYN and CCK, presumably indicating increased synthesis, an increased export from cell somata of VP, OXY, GAL and DYN, and a decrease in levels of these peptides in the posterior pituitary, suggesting increased release. The catecholamine-synthesizing enzyme TH, however, which has a cytoplasmic localization and is not released from nerve endings, remains high in the cell bodies and nerve endings during this state of increased activity.

Ontogeny of Gonadotropin-Releasing Hormone-Containing Neurons in Early Fetal Development of Rhesus Macaques*

Abstract: We studied the ontogeny of GnRH neurons in fetal rhesus macaques from days 36–135 of gestation. The nasal region, pituitary, and brain were dissected, fixed in 4% paraformaldehyde, sectioned on a cryostat at 10 fim, and mounted on slides. Immunocytochemistry and in situ hybridization were performed for GnRH, pro-GnRH, and pro-GnRH mRNA on nasal and brain tissues. Immunoreactive LH, FSH, and PRL were determined in developing pituitary glands. At 36 days, clusters of GnRH cells were found in the nasal region only. GnRH fibers extended into the brain, and large bundles projected laterally toward the basal hypothalamus. By day 38 GnRH cells were also localized in the olfactory region of the brain. With increasing fetal age a gradual caudal extension of GnRH cells occurred. These cells were first observed in the basal hypothalamus at 47 days. Cells containing PRL and gonadotropins (LH and FSH) were detected in the pituitary at 47 and 50 days, respectively. Low levels of pro-GnRH mRNA were present in the nasal ...

Activity of centrally administered galanin fragments on stimulation of feeding behavior and on galanin receptor binding in the rat hypothalamus

Abstract: Synthetic fragments of galanin 1-29 were administered intraventricularly or into the paraventricular nucleus of the hypothalamus for analysis of the critical amino acid sequence necessary to stimulate feeding behavior in rats Galanin 1-29 and galanin fragment 1-16 significantly increased feeding at doses of 6 nmol microinjected into the lateral ventricles and 1 nmol microinjected into the hypothalamus There was no significant effect of D-TRP2 galanin 1-16 microinjected into the hypothalamus, and no significant effect of galanin fragments 1-9, 10-20, 12-29, 17-29, or 21-29 microinjected intraventricularly, on food consumption Synthetic fragments of galanin 1-29 were assayed for displacement of 125I-galanin 1-29 binding to rat hypothalamic membranes The efficacies of the galanin fragments in the feeding paradigm were consistent with the relative affinities of these fragments for the hypothalamic galanin receptor in equilibrium binding experiments The first 16 N-terminal amino acids appear to contain galanin agonist activity on increasing food consumption and to bind to the galanin receptor in the rat hypothalamus

Involvement of transforming growth factor alpha in the release of luteinizing hormone-releasing hormone from the developing female hypothalamus.

Abstract: Little is known about the presence of trophic factors in the hypothalamus and the role they may play in regulating the functional development of hypothalamic neurons. We have investigated the ability of epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha) to affect the release of luteinizing hormone-releasing hormone (LHRH), the neuropeptide that controls reproductive development. We have also determined whether the genes encoding EGF and TGF-alpha are expressed in the prepubertal female hypothalamus. Northern blot analysis of poly(A)+ RNA utilizing a single-stranded EGF cDNA probe failed to reveal the presence of EGF mRNA in either the hypothalamus or the cerebral cortex at any age studied (fetal day 18 to postnatal day 36). In contrast, both a complementary RNA probe and a double-stranded TGF-alpha cDNA recognized in these regions a 4.5-kilobase (kb) mRNA species identical to TGF-alpha mRNA. The abundance of TGF-alpha mRNA was 3-4 times greater in the hypothalamus than in the cerebral cortex. Both EGF and TGF-alpha (2-100 ng/ml) elicited a dose-related increase in LHRH release from the median eminence of juvenile rats in vitro. They also enhanced prostaglandin E2 (PGE2) release. The transforming growth factors TGF-beta 1 and -beta 2 were ineffective. Only a high dose of basic fibroblast growth factor was able to increase LHRH and PGE2 release. Blockade of the EGF receptor transduction mechanism with RG 50864, a selective inhibitor of EGF receptor tyrosine kinase activity, prevented the effect of both EGF and TGF-alpha on LHRH and PGE2 release but failed to inhibit the stimulatory effect of PGE2 on LHRH release. Inhibition of prostaglandin synthesis abolished the effect of TGF-alpha on LHRH, indicating that PGE2 mediates TGF-alpha-induced LHRH release. The results indicate that the effect of EGF and TGF-alpha on LHRH release is mediated by the EGF/TGF-alpha receptor and suggest that TGF-alpha rather than EGF may be the physiological ligand for this interaction. Since in the central nervous system most EGF/TGF-alpha receptors are located on glial cells, the results also raise the possibility that--at the median eminence--TGF-alpha action may involve a glial-neuronal interaction, a mechanism by which the trophic factor first stimulates PGE2 release from glial cells, and then PGE2 elicits LHRH from the neuronal terminals.