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PubMed1994

Early neurogenesis in the anterior hypothalamus of the rhesus monkey.

The time of formation of neurons of the various nuclei of the anterior hypothalamus of the rhesus monkey has been determined using [3H]thymidine autoradiography. Plotting of heavily radiolabeled nuclei indicate that in the macaque monkey neurons of the hypothalamus are generated during three weeks, between the 27th and 48th day of the 165 gestational period of this species. The individual nuclei generally display two waves of neuronal generation. Furthermore, a caudolateral to rostromedial gradient of neurogenesis has been observed in the supraoptic nucleus and a dorsal to ventral gradient in the paraventricular nucleus. Thus, neurons of the primate hypothalamus are generated at a much earlier stage of gestation and their generation lasts about three times longer than in rodents. However, most of the basic neurogenetic gradients are remarkably similar, in spite of species specific differences in cytoarchitecture of specific nuclei.

Animals↗

PubMed1990

Changes of NGF level in mouse hypothalamus following intermale aggressive behaviour: biological and immunohistochemical evidence.

Nerve growth factor (NGF) immunoreactivity was detected in the hypothalamus of adult male mice. NGF-immunoreactive cell bodies were examined through consecutive brain sections, and it was found that most of the NGF-positive cells were located in the dorsomedial and mediolateral portions of the hypothalamus. Tissue culture bioassays showed that hypothalamic extract elicits neurite outgrowth from both chick sensory ganglia and rat superior cervical ganglia neurons, and that these effects are inhibited by addition of NGF antibodies. Our results also showed that intermale aggressive behaviour induced by 6-8 weeks of social isolation induces an NGF increase in the hypothalamic area, which is not abolished by sialoadenectomy, suggesting that the increased brain NGF is locally synthesized, and does not come from salivary sources. Likewise, the level of NGF in the hypothalamus of adrenalectomized fighting mice increased, although to a much lesser extent, when compared to hypothalamic levels of sham-operated fighting mice. The present results and a recent report showing that aggressive behaviour causes an increase of mRNANGF in hypothalamic areas are discussed in relation to a possible functional role of NGF in these brain structures.

Aggression↗

PubMed1986

In vitro release of growth hormone-releasing factor from rat hypothalamus: effect of insulin-like growth factor-1.

The release of growth hormone-releasing factor (GHRF) from rat hypothalamus was investigated in vitro. After 60 min preincubation the released GHRF from sliced rat hypothalamic fragments during 60 min incubation was detected by a highly specific and sensitive radioimmunoassay for rat GHRF. The release of GHRF was Ca2+-dependent and enhanced by high concentration of K+. Insulin-like growth factor-1 (IGF-1) significantly decreased GHRF release to 65% and 84% of the control at concentrations of 10(-8) M and 10(-7) M, respectively. These results suggest that this in vitro system is useful for the investigation of the mechanism of GHRF release from the hypothalamus and that IGF-1 is probably involved in the feedback inhibition of growth hormone secretion by attenuating GHRF release from the hypothalamus besides countering the effect of GHRF on the pituitary.

Animals↗

PubMed1990

Ethanol-related changes in substance P in the hypothalamus and anterior pituitary.

The effect of the administration of a rabbit anti-substance P serum (ASPS) was studied in rats receiving an acute injection of ethanol. ASPS lowered serum prolactin levels and reduced the hyperprolactinemia induced by ethanol. ASPS also decreased LH serum levels in both saline- and ethanol-treated rats. The effect of ethanol on the concentration of substance P-like immunoreactivity (SP-LI) in the mediobasal hypothalamus and the anterior pituitary gland was also investigated. Ethanol reduced SP-LI in the mediobasal hypothalamus but increased it in the anterior pituitary gland. The presence of ethanol (50 mM) did not affect the K(+)-evoked release of SP-LI from either mediobasal hypothalamus or anterior pituitary gland, though it increased the SP-LI concentration remaining in this gland. These results indicate that ethanol increases the content of SP-LI in the anterior pituitary gland and suggest that substance P may be involved in the prolactin release induced by the acute administration of ethanol.

Animals↗

PubMed1988

Cardiac arrhythmias induced in cats by stimulation of the anteromedial hypothalamus.

Negative emotional behavior induced during stimulation of the anteromedial hypothalamus is frequently accompanied by cardiac arrhythmias just after cessation of the stimulation (the poststimulus arrhythmias: the PSAs). A mechanism related to the PSAs may be neurogenic in origin. Whether or not the PSAs are influenced by hypothalamically induced adrenal catecholamines has not been settled. We assessed the correlation between these influences on the PSAs induced by anteromedial hypothalamic stimulation in anesthetized cats. Thirty-five adult cats were given stimulation through an electrode inserted stereotaxically into the hypothalamus and arterial blood pressure, electrocardiogram and heart rate were recorded on a polygraph. PSAs were never observed after vagotomy and intravenous injections of methyl-atropine and phentolamine. Carteolol was without effect. When an intentional gradual reduction of stimulus intensity was applied instead of sudden cessation of hypothalamic stimulation, there was a gradual decline in the blood pressure and no PSAs. Adrenalectomy did not alter the threshold for the PSAs but did reduce the frequency of the PSAs. Intravenous injections of catecholamines produced cardiac arrhythmias similar to those seen in PSAs. After vagotomy, stimulation of the distal nerve of the right vagus during or just after hypothalamic stimulation produced the same arrhythmias as seen in PSAs, but vagus stimulation alone did not. These results suggest that the PSAs are due to 'sudden' change from sympathetic to parasympathetic influences on the heart and that adrenal catecholamines are involved in the prolongation of the train of the PSAs. These findings support the proposal that the PSAs are a stress-related symptom induced by stimulation of the anteromedial hypothalamus.

Adrenal Medulla↗

PubMed1985

Topographic organization of projections from the amygdala to the hypothalamus of the rat.

Afferent fibers from the amygdala to subdivisions of lateral, ventromedial and dorsomedial hypothalamic nuclei were investigated in rat by retrograde transport of horseradish peroxidase. Small (intranuclear size) peroxidase deposits were placed in hypothalamic nuclei by iontophoresis of a tracer solution containing poly-L-alpha-ornithine which greatly limited diffusion. The medial, central and amygdalo-hippocampal nuclei of the amygdala were found to be the major donors of amygdaloid afferent fibers to the hypothalamus, but there was also substantial labeling of somata in cortical, basomedial, basolateral and lateral amygdaloid nuclei and the intra-amygdaloid bed nucleus of the stria terminalis. No fibers projected from the posterior cortical nucleus of the amygdala to the hypothalamus. Most amygdaloid projections to the lateral hypothalamic area originated in the anterior half of the amygdala, while projections to the ventromedial hypothalamic nucleus arose along the entire length of the amygdala except the posterior cortical nucleus. The amygdalo-hippocampal area projects to the medial hypothalamus. Other amygdaloid nuclei project to both the medial and lateral hypothalamic nuclei. These topographic organizations of amygdaloid afferent fibers to various subdivisions of the hypothalamic nuclei are discussed and compared with other anatomical studies on these connections.

Amygdala↗

PubMed1991

Food deprivation and age modulate neuropeptide gene expression in the murine hypothalamus and adrenal gland.

We have developed a rapid and simple method for quantitative Northern blot analysis of rare messenger RNA species from single mouse hypothalami and adrenals. This technique has allowed us to study the effects of food deprivation on neuropeptide gene expression in the mouse hypothalamus and adrenal gland. The potential modulatory effects of sex and age were also investigated. Food deprivation induced a two-fold increase in the amount of hypothalamic neuropeptide Y (NPY) mRNA, but did not increase NPY mRNA in the brainstem. Age had a significant effect on levels of NPY messenger RNA levels in the hypothalamus. However, there were no gender-associated effects. Sexually immature females (6 weeks old) had higher levels of NPY expression than mature females (9 weeks old). In contrast, in the adrenal gland, increasing maturity was associated with higher levels of NPY mRNA. As in the hypothalamus, fasting caused approximately two-fold increases in NPY mRNA over levels in the ad libitum fed state for both mature and immature mice. Thus, hypothalamic NPY neurons are responsive to nutritional deprivation and developmental status, suggesting that NPY neurons may be important in energy homeostasis.

Adrenal Glands↗

PubMed1996

Effect of morphine on proopiomelanocortin gene expression and peptide levels in the hypothalamus.

Opiates have been reported to suppress POMC in the medial basal hypothalamus (MBH) but studies have been complicated by the fact that acutely, in the rat, opiates stimulate corticosterone and inhibit gonadal steroid release, which could both affect POMC in brain. We have therefore examined POMC gene expression and peptide levels in the MBH of castrated rats after 10 days of treatment with subcutaneous morphine or placebo pellets and after pellet removal. POMC mRNA was measured by solution hybridization assay and beta-endorphin (beta-EP) and alpha-MSH were measured by RIA. In castrated male rats, the mean POMC mRNA concentration in the MBH was 1.67 +/- 0.11 pg/microgram RNA in the control animals and decreased to 1.17 +/- 0.11 pg/microgram RNA in the morphine-treated animals (P < 0.01). Similarly in castrated, estradiol replaced female rats, the mean POMC mRNA level in the MBH was 1.36 +/- 0.19 pg/microgram RNA and decreased to 0.82 +/- 0.08 pg/microgram RNA after morphine treatment (P < 0.05). beta-EP levels were not significantly different in either study. When castrated male rats were similarly morphine pelleted and killed either on day 10 or 2 days later after pellet removal, the mean POMC mRNA level again fell from 1.83 +/- 0.21 in the controls to 1.28 +/- 0.20 pg/microgram RNA after 10 days of morphine; 2 days after pellet removal levels remained suppressed at 0.80 +/- 0.08 pg/microgram RNA (P < 0.01). In this study the concentrations of beta-EP and alpha-MSH were both noted to decline in the MBH after morphine treatment (P < 0.05). When the forms of beta-EP in the MBH were characterized by HPLC, a decrease in the concentration of beta-EP was again seen after morphine but no significant differences in the pattern of beta-EP processing or in the relative amounts of beta-EP1-31 compared to beta-EP1-27 and beta-EP1-26 were noted in morphine-treated animals. There was also no significant effect of 10(-6)-10(-4) M morphine on basal or KCl-stimulated release of beta-EP or gamma 3-MSH release from the perifused rat hypothalamus in vitro. We conclude that morphine suppresses POMC gene expression in the hypothalamus of chronically treated male and female rats. Persistent changes were also noted during morphine withdrawal. In some cases this was accompanied by a fall in beta-EP peptide content. These effects were seen in castrated animals with and without sex steroid replacement and are thus independent of the effects of morphine on the pituitary-gonadal axis. These results show that opiate drugs modify endogenous opioid systems in the brain and provide further support for the hypothesis that such changes may contribute to mechanisms of opiate dependence and withdrawal.

Animals↗

PubMedDate not supplied

Immunohistochemical and immunocytochemical localization of gamma-melanocyte stimulating hormone (gamma-MSH)-like immunoreactivity in human and rat hypothalamus.

Immunohistochemical localization of gamma-MSH was studied in human and rat hypothalamus by peroxidase-labeled antibody method both at light and electron microscopic levels. Human and rat hypothalamus contained immunoreactive gamma-MSH neurons and varicose nerve fibers. The distribution of gamma-MSH-positive nerve fibers was similar to that of beta-endorphin previously reported. By our "re-staining method," gamma-MSH and ACTH were localized in the same neurons and nerve fibers. In the rat, the immunologic staining of gamma-MSH in hypothalamic neurons and nerve fibers was not diminished after hypophysectomy. These findings strongly suggest the possibility of actual precursor production in the hypothalamus which is similar to that in the anterior pituitary. The presence of gamma-MSH at the synapse-like structure of the nerve terminal may indicate that gamma-MSH could function as a neurotransmitter or a neuromodulator.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

A group of neurons highly reactive for enkephalins in the rat hypothalamus.

Enkephalin-like immunoreactivity was demonstrated in a group of highly reactive neurons (HRN) of the rat hypothalamus by the biotin-avidin immunohistochemical technique. The location of the HRN spans several nuclei but the consistent immunoreactivity, the constant topography, and the uniform dimensions of the neurons suggest that they belong to one group. At its caudal end the group appears within the rostral dorso-medial nucleus. At the level of the caudal paraventricular nucleus (PVH) the HRN are assembled in a spherical pattern around a subgroup of neurons in the anterior hypothalamus (AH). The HRN then are found in a position directly between the PVH and the fornix. Before the HRN disappear at the level of the caudal preoptic area, many of the HRN become associated with the fornix. The close association of the HRN with the AH subgroup and the fornix suggests that the HRN may influence the activity of these structures. The HRN are small to medium in size and their short processes suggest that the HRN communicate with other neurons in their vicinity. The areas of the hypothalamus in which the HRN are found are involved in neuroendocrine and thermoregulatory functions suggesting that the HRN may play a role in modifying the activity of neurons and fibres involved in these functions.

Animals↗

PubMedDate not supplied

Localization of neuropeptide Y-like immunoreactivity in the cat hypothalamus.

The distribution pattern of neuropeptide Y-like immunoreactivity (NPY-Li) in cat hypothalamus was studied using avidin-biotin modification of immunocytochemical method. This study showed cell bodies containing NPY-Li in the periventricular and the infundibular nuclei and also a moderate number of neurons with NPY-Li in the ventromedial nucleus, an observation not reported in earlier studies. Fibers with NPY-Li were noted throughout the hypothalamus, but most prominently within the periventricular regions. The location of NPY cells within the hypothalamus suggests the possibility of an interaction with dopaminergic and other proopiomelanocortinergic neurons.

Animals↗

PubMedDate not supplied

Neurotensin-like immunoreactivity in the pituitary and hypothalamus of bony fishes.

Using an antiserum raised against synthetic neurotensin (NT), the distribution of immunoreactivity in the pituitary and hypothalamus has been examined by immunocytochemistry at light and electron microscope level in a number of species of bony fishes. In most species immunoreactive perikarya were found in the preoptic region of the hypothalamus, with fibres throughout the tuberal hypothalamus and neurohypophysis (neural lobe and median eminence). In the neurohypophysis of teleosts NT-like immunoreactivity was seen in a dense band of fibres bordering the ACTH cells of the rostral pars distalis: absorption controls showed that this was due to the presence of an NT(8-13)-like or xenopsin-like sequence, which, according to electron microscopic observations, was contained in small dense cored vesicles. The antiserum also stained the pituitary ACTH cells of some species, apparently due to cross-reaction with the 17-19 sequence of ACTH. These results suggest that an NT-like peptide may have a role in control of the adenohypophysis in fishes.

Animals↗

PubMedDate not supplied

MSG effects on beta-endorphin and alpha-MSH in the hypothalamus and caudal medulla.

Monosodium glutamate (MSG) was given to neonatal male rats to determine its effects on neurons containing beta-endorphin (beta-END) and alpha-melanocyte stimulating hormone (alpha-MSH) within the basal hypothalamus (arcuate nucleus) and caudal medulla [nucleus tractus solitarius (NTS)] and on the levels of beta-END and alpha-MSH within these areas. Immunocytochemical studies demonstrated a reduction in the number of cells within the medial hypothalamic area (arcuate nucleus) among MSG-treated animals versus saline controls. MSG did not reduce the number of cell bodies within the caudal medulla (NTS). MSG significantly reduced beta-END and alpha-MSH immunoreactive levels in the basal hypothalamus as determined by radioimmunoassay. Whereas a significant reduction in the level of beta-END occurred in the ventral caudal medulla (VCM), none occurred in the dorsal caudal medulla (DCM). In contrast, levels of alpha-MSH increased significantly in the DCM among animals receiving MSG compared to control animals. This study documents the contribution of beta-endorphin containing neurons of the basal hypothalamus to areas of the caudal medulla. The effect of MSG on beta-endorphin and alpha-MSH neurons in these areas and their differential effects on levels in the caudal medulla areas raises questions about the sites of origin of these peptides.

Animals↗

PubMedDate not supplied

Neurotensin perfused in hypothalamus of sated or fasted rat: HPLC analysis of release of DA, NE and 5-HT and their metabolites.

This investigation was undertaken in the unrestrained rat to determine the localized effect of neurotensin (NT) on the profile of release and turnover of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) within the hypothalamus. Following stereotaxic implantation of a permanent guide tube, artificial CSF was perfused in the hypothalamus of the freely moving animal by means of push-pull cannulae at a rate of 20 microliters/min and for an interval of 5.0 min. After three 5.0 min control samples were collected, NT in a concentration of 0.1 micrograms/microliter was perfused followed by additional CSF controls. Assay by HPLC-EC of each perfusate showed that when the rat was sated, NT evoked a significant increase in the release of DA and DOPAC from the hypothalamus as well as augmented NE turnover, as reflected by a significant efflux in MHPG. However, when the rat was fasted for 22 hr, the perfusion of NT reduced DA and DOPAC concentrations in the diencephalic perfusate significantly as well as levels of both MHPG and VMA. Under both sated and fasted conditions, NT failed to produce notable changes in the release of 5-HT or its metabolism to 5-HIAA. These findings thus reveal a functional interaction between NT and both of the catecholamine neurotransmitters within hypothalamic neurons, which is clearly dependent upon the nutritional status of the animal.

Animals↗

PubMed1994

An in situ hybridization and immunohistochemical study of vasotocin neurons in the hypothalamus of water-deprived chickens.

The distribution of immunoreactive vasotocin (IR-AVT) and AVT mRNA in the hypothalamus of White Leghorn cocks was determined by immunohistochemistry and in situ hybridization, respectively. In control birds that were provided with water ad lib, AVT mRNA was distributed in the periventricular and lateral regions of the hypothalamus in clusters of neurons that correspond structurally with the mammalian paraventricular (PVN) and supraoptic (SON) nuclei. Although the distribution of AVT, identified by immunohistochemistry of adjacent serial sections within the hypothalamus, was similar to the distribution of AVT mRNA, the possibility that some positive staining was due to mesotocin neurons was not excluded. Water deprivation for 2 and 4 days resulted in both an increase in levels of AVT mRNA per neuron and the number of AVT mRNA-containing cells. Additionally, water deprivation resulted in a decrease in the amount of IR-AVT per neuron. The results indicate that osmotic stimulation increases AVT gene expression not only in individual neurons but also by activating subpopulation of neurons that are not observed in normally hydrated birds.

Animals↗

PubMed1981

Immunoreactive beta-endorphin in the plasma, pituitary and hypothalamus of young and old male rats.

Immunoreactive beta-endorphin (IR-beta-ENDO) was measured in the plasma, pituitary, and hypothalamus of young (3-5 mo.) and old (19-23 mo.) male Sprague-Dawley rats, using a specific radioimmunoassay. Plasma IR-beta-ENDO in old male rats (3.44 +/- 0.54 ng/ml) was more than three times higher than values observed in young male rats (1.00 +/- 0.10 ng/ml). Pituitary content and concentration of IR-beta-ENDO also were significantly greater in the old (5.85 +/- 0.51 microgram/gland and 1.17 +/- 0.10 microgram/mg protein) than in the young (3.53 +/- 0.29 microgram/gland and 0.78 +/- 0.06 microgram/mg protein) male rats. The content of IR-beta-ENDO in the hypothalamus of old and young rats was nearly the same (43.45 +/- 2.47 and 49.88 +/- 6.35 ng/hypothalamus, respectively), whereas the concentration of IR-beta-ENDO in the hypothalamus of the old male rats (3.89 +/- 0.25 ng/mg protein) was approximately 50% lower than that observed in the young male rats (7,80 +/- 0.85 ng/mg protein). These changes in plasma, pituitary, and hypothalamic IR-beta-ENDO may contribute to the increase in prolactin and decrease in gonadotropins observed in old male rats, since beta-ENDO administration is known to produce these effects on prolactin and gonadotropin secretion.

Aging↗

PubMed1985

Age-associated alteration of serotonergic synaptic neurochemistry in rat rostral hypothalamus.

Levels of monoamines and metabolites in rostral and caudal hypothalamic fragments of young (3-4 months) and old (25-26 months) Fischer 344-rats were compared. There were no differences between fragments of young animals. In senescent rats, 5-hydroxyindoleacetic acid (5HIAA) increased in both rostral and caudal hypothalamus. The ratio 5HIAA/5HT (serotonin), an index of serotonin turnover, increased only rostrally. This age-related increase of 5HIAA/5HT in rostral hypothalamus was associated with a decrease in [3H]-spiperone binding. There were no age-related changes of MAO-A activity in the hypothalamus or of serum tyrosine or tryptophan levels.

Aging↗

PubMedDate not supplied

Somatostatin gene expression in hypothalamus and cortex of aging male rats.

Somatostatin has been reported to decrease with age in many brain regions and these changes generally have been considered to have important implications for the regulation of both neural activity and neuroendocrine regulatory systems. The purpose of this study was to determine whether the age-related changes in somatostatin concentration in cortex and hypothalamus are attributable to alterations in the regulation of somatostatin gene expression. Hypothalamic and cortical tissue were dissected from young (3-4 month), middle-aged (12-14 month), and old (22 month) male Fischer 344 rats. Total RNA was extracted and dilutions blotted to nitrocellulose. Somatostatin cDNA in expression vector pSP65 was used to produce a 32P-labeled antisense probe for hybridization. After washing, blots were autoradiographed and analyzed by densitometry. Dilutions of total RNA were also probed with 32P-labeled oligo d(pT)16 to determine poly A +RNA levels. Data were expressed as relative somatostatin gene expression (somatostatin mRNA/poly A +RNA). Results indicated that in cortex, relative somatostatin gene expression was similar in young, middle-aged, and old animals (0.54 +/- 0.11, 0.60 +/- 0.08, and 0.51 +/- 0.04, respectively). However, somatostatin gene expression in the hypothalamus decreased consistently with age and ratios in old rats were approximately 50% of levels observed in young animals (p less than 0.05). Northern analysis of RNA revealed a single somatostatin transcript of approximately 0.65 kb in all age groups. In situ hybridization analysis of somatostatin mRNA in the hypothalamus indicated that the age-related decrease in somatostatin gene expression is a consequence of decreased expression within specific hypothalamic nuclei rather than a loss of somatostatin-containing neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗