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PubMedDate not supplied

[Bioelectric and vegetative reactions of the rat to stimulation of the ventromedial hypothalamus].

Neurophysiological and correlational analysis was carried out to investigate the influence of stimulation of negative zones in the ventromedial hypothalamus on dynamics of electroencephalographic and vegetative parameters. The stimulation used led to an appearance of theta-rhythm initially in the stimulated structure, followed by an increase of plasticity of the system of bioelectrogenesis and regulation of vegetative functions. Stimulation of the negative zones of the ventromedial hypothalamus led to a formation of pathological excitation focus mainly at the limbic level with special cyclic type of cortico-subcortical relations. Increase of rigidity of the systems of electrogenesis and regulation of vegetative functions was accompanied by a formation of closed reverberatory cycle of integrations of the hypothalamus, hippocampus, and neocortex and by a change in autocorrelational functions reflecting an increase of general synchroneity .

Animals↗
PubMed1984

[Electrophysiological and catecholamine mechanisms of negative feedback in regulation of the hypothalamus by male sex glands].

The immediate response on the part of the sympathoadrenal system (SAS) in mature male rats to testosterone propionate involves an increase in the content of dopamine and lowering of adrenaline and noradrenaline content in the hypothalamus, brain cortex, adrenals and peripheral organs, paralleled by an increase in the amplitude of evoked potentials and reduction in the frequency of induced impulse activity of arcuate neurons of the hypothalamus. This attests to the specificity of the associated response of the SAS and the hypothalamus-pituitary-gonadal system (HPGS) to hyperandrogenization and to the dopaminergic nature of the negative feed-back mechanism in the HPGS.

Adrenal Glands↗
PubMed1980

Purification and properties of thyrotrophin releasing hormone (TRH)-containing particles from the rat hypothalamus.

The subcellular distribution of the TRH-like immunoreactivity in the rat hypothalamus and brain was studied. In differential centrifugation, the 900 g for 10 min supernatant (S1) of the hypothalamus or brain contained 61--79% of the total TRH. At 11,000 g for 20 min, 51--73% of the TRH in S1 was sedimented. When the hypothalamic S1 was fractioned under non-equilibrium conditions at 25 degrees C, two populations of TRH-containing particles were observed in several types of continuous linear density gradients. Metrizamide and sucrose gradients affected TRH-assay. TRH-particles were very light in Percol-gradients. Isotonic dextran 40,000-sucrose gradients gave the most reproducible results. In these gradients, the large TRH-particles (35%) equilibrated at 1.055--1.060 kg/l and the small ones (23%) at 1.041--1.047 kg/l. Working at 4 degrees C decreased the amount of large TRH-particles. The apparently larger particles contained cytoplasmic and mitochondrial enzymes and were sensitive to hypoosmotic shock like synaptosomes. Electron micrographs confirmed that these particles were synaptosomes. The true nature of the small particles remained unclear but morphologically a part of them were also synaptosomes. Treatment of the animals with reserpine (10 mg/kg i.p., 24 h), with 6-hydroxydopamine (100 microgram/rat i.c.v.) or with 5,7-dihydroxytryptamine (200 microgram/rat i.c.v.) did not affect significantly TRH-recovery or distribution in the hypothalamus.

Animals↗
PubMedDate not supplied

[Dynamics of the changes in the content of testosterone and estradiol receptors in the hypothalamus of male rats in the course of sexual development].

The content of receptors to testosterone and estradiol in hypothalamus of the male rats was studied during their sexual maturation (7, 14, 21, 28, 35 and 42 days). In all the age groups of animals the concentration of receptors to testosterone in the cytoplasmic and nuclear fractions of hypothalamus was at a relatively constant level, except in 7 day old males in which the minimal concentration of cytoplasmic and the maximal concentration of nuclear receptors were noted. The highest values of estradiol-binding sites in cytosol of hypothalamus were observed on the 7th and 14th days and in the nuclear fraction on the 28th, 35th and 42nd days of life. The binding of both the hormones with their receptors is a specific process characterized by a high affinity. A suggestion is put forward that receptors both to androgens and estrogens take part in the brain sexual differentiation.

Aging↗
PubMed1982

Unilateral posterior deafferentation of hypothalamus and mitotic activity of thyroid follicular cells under normal conditions and after hemithyroidectomy.

The effect of unilateral posterior deafferentation of the hypothalamus on the mitotic activity of thyroid follicular cells was studied in hemithyroidectomized and sham-operated rats. Left side posterior deafferentation of the hypothalamus reduced significantly the basal mitotic activity of both thyroid lobes and prevented the hemithyroidectomy-induced increase in mitotic activity of the remaining thyroid lobe. Right side posterior deafferentation of the hypothalamus or sham operation did not interfere with the normal or stimulated activity of the follicular cells. These data suggest left side dominance in the mitosis control of the thyroid cells but the mechanism resulting in these findings remains unclear.

Afferent Pathways↗
PubMed1981

[Effect of removal of the hypothalamus and pituitary gland from rat fetuses on the development of pancreatic B-cell function].

The reactivity of pancreatic B-cells of the decapitated and encephalectomized rat foetuses was determined by changes of insulin secretion in response to glucose introduction in the incubation medium. Upon removal of hypophysis together with hypothalamus in the intact rat females and females with alloxanic diabetes on the 17.5-18.5 day of prenatal development, their pancreas, unlike that of the control foetuses, remained refractory to glucose on the 21.5 day of development. The removal of hypothalamus only upon encephalectomy of the foetuses of the same age led to a similar effect, thus suggesting possible influence of hypothalamus on the regulation of functional maturation of the pancreatic B-cells in the end of prenatal development. Upon the combined incubation of pancreas fragments of the decapitated rat foetuses with adenohypophyses of the adult rats, the effect of decapitation was cut short and the gland responded by the increase of insulin secretion to the rise of glucose content in the medium.

Alloxan↗
PubMed1978

[Effect of stimulation of the preoptic region of the hypothalamus on the activity of individual optic tract fibers in rabbits].

Statistical background characteristics and impulse activity of some fibres of the optical tract evoked by light flashes were compared before and after stimulation of the preoptic hypothalamic region in listenin-immobilized rabbits. It was shown that the influence of the high frequency preoptical hypothalamus stimulation correlates with the pattern of responses to light flashes observed when recording from the optical tract fibres. In most cases the preoptical hypothalamus stimulation caused an increase of the background activity and facilitation of responses to light flashes. Phasic response to a light flash with short latency (42 ms), consisting of a long train of pulses and tonic responses with long latency (155 ms) were facilitated to a greater extent. The facilitation of short-latent (35 ms) phasic responses to a light flash consisting of a short train of phases after the preoptical hypothalamus stimulation was not clearly pronounced or was inhibited.

Animals↗
PubMed1982

[Dependence on androgen metabolism in the hypophysis and hypothalamus on age in rats].

The in vitro metabolism of 3H-testosterone, 3H-dihydrotestosterone, 3H-5 alpha-androstan-3 alpha, 17 beta-diol and 3H-5 alpha-androstan-3 beta, 17 beta-diol was studied in hypophyses and hypothalamuses of the rats at the age from 5 to 60 days. The androgen metabolites were separated by means of chromatography in thin layers of silicogel. The rate of androgen metabolism in the organs studied from the 5th till the 23rd day of development was dozens of times that in the adult animals. Sexual dimorphism was also shown. 3H-5 alpha-androstan-3 beta, 17 beta-diol transforms in hypothalamuses and hypophyses of the rats of all age groups of both sexes into polar metabolites only. A suggestion is put forward to the effect that the extensive metabolism of androgens in the brain until the 23rd day of development is due to the development of the system hypothalamus-hypophysis-gonads, depends on the concentration of androgens circulating in the blood and is directed to control the secretion of gonadotropins. The above period of development is termed as "critical".

Aging↗
PubMed1982

[Effect of destruction of the paraventricular and mediobasal sections of the hypothalamus on the course of pain shock in rabbits].

Experiments were made on conscious rabbits with pain shock induced by electric stimulation of the sciatic nerve. Destruction of the paraventricular hypothalamus (primarily of the dorsomedial and paraventricular hypothalamus (primarily of the dorsomedial and paraventricular nuclei) was found to lead, in the presence of shock development, to AP rise, normalization of the heart and respiration rates within 5 to 10 minutes after the destruction. Three out of the 6 animals survived. At the same time destruction of the mediobasal hypothalamus (the arcuate and ventromedial nuclei) did not entail any marked changes in the cardiovascular system. Further progress of shock and the time of the death of all the animals of the latter group did not significantly differ from those seen in the sham-operated animals' group where all animals also died.

Animals↗
PubMed1978

[Functional morphology of accessory neurosecretory cells in cat hypothalamus].

In acute experiments on tomcats after stimulation of supraoptic nuclei (SON), postoptic nuclei (PON), preoptic area of the hypothalamus, cervical sympathetic nerve (SCN) and vagal afferent fibers (VA) the following data were obtained in the preparations stained by Gomori method: four pair accessory cell groups in the rostral part of the hypothalamus were observed: 1) periventricular group (along the walls of the III ventricle; 2) the preoptic group (above the preoptic recess; 3) the parafornical group (around the fornix columns), and 4) the spindle-shaped group. The latter group was revealed constantly both in control and in the stimulated animals in all the experiments. In direct stimulation of the SON and PON and also if the CSN and the vagus direction of its reaction coincided with such in the SON and PON, whereas in stimulation of the VA of the hypothalamus the synthesis activation was observed against the background of unchanged (in comparison with control) state of the neurosecretory nuclei.

Animals↗
PubMedDate not supplied

Bile flow impairment of ventro-medial hypothalamus lesioned obese rats.

Cholesterol supersaturation of bile has been reported in human obesity. Since electrolytic lesions placed in the ventro-medial hypothalamus induce hyperphagia and obesity in the rat, bile flow and lipid composition have been studied two months after the induction of such stereotaxic lesions in a group of ten animals and in their sham-operated controls. Bile flow was significantly lower in obese rats than in controls. The bile flow reduction was attributed to a decrease of the bile acid independent fraction, since no variation in bile acid excretion rate and in bile to plasma ratio of [14C] erythritol was seen between the two groups. Whereas plasma cholesterol and triglycerides were higher in ventro-medial hypothalamus lesioned rats, biliary cholesterol and phospholipid excretion rates were similar in the two groups. These data indicate that stereotaxic lesions of ventro-medial hypothalamus in the rat significantly reduce bile flow, suggesting a correlation between active sodium transport at canalicular level and neuroendocrine hypothalamic function, but fail to induce qualitative alterations of bile lipid composition.

Animals↗
PubMed1981

The effect of starvation, restricted feed intake and refeeding on acid phosphatase activity of the hypothalamus and frontal cerebral cortex of the rat.

Acid phosphatase (EC: 3.1.3.2) activity at the hypothalamus and frontal cerebral cortex has been studied in male rats maintained on different dietary regimes. The enzyme activity in the cerebral cortex did not undergo any observable changes in any of the experimental groups. Enzyme activity in the hypothalamus, rose after food deprivation in both acutely and chronically starved rats, while the enzyme activity returned to physiological levels in refed animals. The hypothalamus neuroendocrine role and a possible interregional heterogeneity for acid phosphatase in rat brain might explain the two enzymic activity patterns observed in the present experiment.

Acid Phosphatase↗
PubMedDate not supplied

Substance P-like content in the hypothalamus of water-deprived rats.

The content of substance P-like in the hypothalamus of control and dehydrated rats was determined by bioassay on isolated jejunum of rabbits. Depriving the rats of drinking water for twelve days caused statistically significant increase of the substance P-like in the hypothalamus. These results suggest that water deprivation increases the synthesis of substance P-like in the rat hypothalamus.

Animals↗
PubMed1995

[Effect of angiotensin II on vasopressin gene transcription in the hypothalamus of rats].

Experiments were carried out in male Sprague-Dawley rats. 3'-end digoxigenin-labeled 26 bp oligonucliotide probe was used to detect the vasopressin (AVP) mRNA in the hypothalamus. Dot blotting technique was used in the investigation of AVP gene transcription level. The results showed that continuous intracerebroventricular administration (i.c.v.) of angiotensin II at a rate of 0.2 nmol/h for 2 days by using a miniosmotic pump resulted in a significant increase in daily water intake. An increase of AVP gene transcription level in the hypothalamus was also observed, but statistically insignificant. When daily water intake was limited (25 ml/d), continuous i.c.v. infusion of ANG II caused a significant increase in hypothalamic AVP gene transcription. It was also observed that hypothalamic AVP gene transcription level increased after salt loading and dehydration. However, intraperitoneal application of angiotensin converting enzyme inhibitor captopril (5 mg/(kg.d)) or i.c.v. nonpeptide angiotensin II receptor antagonist Dup753 (0.9 nmol/h) did not attenuate the increase of AVP gene transcription level induced by salt loading or dehydration. It is therefore suggested that the administration of ANG II enhances AVP gene transcription in the hypothalamus, especially when water intake is limited. However, this increase does not involve the participation of endogenous ANG II.

Angiotensin II↗
PubMed1995

Neurochemical identity of neurones expressing oestrogen and androgen receptors in sheep hypothalamus.

Gonadal steroids exert important feedback influences on hypothalamic neurones involved in regulating reproductive behaviour and pituitary hormone secretion. The recent development of antibodies specific for individual gonadal steroid receptors has been of great use in determining precisely which cells in the hypothalamus express androgen, oestrogen and progesterone receptors. In the sheep brain, both oestrogen and androgen receptor antibodies have been used successfully and the distribution of cells expressing both receptors has now been determined in ewes and rams, respectively. In addition, the predominantly nuclear localization of the steroid receptors has enabled double-labelling immunocytochemical procedures to determine the neurochemical phenotype of neurones expressing the steroid receptor. Work in the sheep hypothalamus shows that gonadotrophin-releasing hormone neurones do not possess oestrogen or androgen receptors. However, substantial numbers of cells containing oestrogen receptors in the preoptic area of ewes contain the inhibitory neurotransmitter gamma aminobutyric acid, while most oestrogen receptor-immunoreactive neurones in the ventromedial nucleus synthesize the inhibitory neuropeptide somatostatin. Androgen receptors have been detected in many of the ventromedial somatostatin neurones in rams. In contrast, the neurochemical phenotype of the great majority of oestrogen and androgen receptor-immunoreactive cells in the arcuate nucleus remains unknown. The identification of the neurotransmitters and neuropeptides synthesized by neurones possessing androgen and oestrogen receptors in different regions of the ovine hypothalamus provides a neuroanatomical basis for understanding the mechanisms by which gonadal steroids regulate reproductive function.

Animals↗
PubMed1995

Localization of Na, K-ATPase isoforms in the hypothalamus of the rat.

In situ hybridization histochemistry with synthetic oligonucleotide probes was used to localize mRNAs encoding three isoforms of the catalytic (alpha) subunit and one isoform of the (beta) subunit of the Na, K-ATPase in rat hypothalamus using contact film radioautography. 3H-Ouabain binding to specific anatomical nuclei in the hypothalamus was determined using a quantitative radioautographic technique previously developed in our laboratory. Specific hybridization was found with oligonucleotide probes for mRNA encoding alpha 1, alpha 2, alpha 3, beta 1 isoforms of the Na, K-ATPase. High levels of hybridization signal for alpha 3 and beta 1 were found in ventromedial hypothalamus, supraoptic nucleus, paraventricular nucleus and the anterior hypothalamic area. Very low levels of hybridization for all isoforms were found in the optic chiasm. mRNAs encoding alpha 1 and alpha 2 isoforms were expressed at lower levels than alpha 3. The distribution of alpha 2 was consistent with expression in glial cells. Generally, levels of alpha 1 mRNA were higher in the arcuate nucleus than in other hypothalamic regions and very low levels were found in the anterior hypothalamic area. 3H-Ouabain binding was relatively diffuse, consistent with the localization of the synthesized Na, K-ATPase protein in cellular processes. The number of 3H-ouabain binding sites in the paraventricular nucleus was significantly lower than other hypothalamic nuclei studied. The results suggest that Na, K-ATPase isoforms may be differentially expressed in hypothalamic nuclei.

Animals↗
PubMed1995

Identification of 5-hydroxytryptamine7 receptor binding sites in rat hypothalamus: sensitivity to chronic antidepressant treatment.

Due to the high level of expression of mRNA for the 5-hydroxytrytamine (5-ht7) receptor in the hypothalamus and the high affinity of 5-HT for this receptor, [3H]5-HT binding was performed in rat hypothalamus to determine whether 5-ht7 receptor binding sites are present in animal tissue. [3H]5-HT binding was performed in the presence of 100 nM pindolol, which is inactive at 5-ht7 receptors but prevents the binding of [3H]5-HT to 5-HT1A and 5-HT1B receptor binding sites. Under these conditions, [3H]5-HT bound to a binding site with an affinity of 1.94 nM. Displacement studies showed the pharmacology of the hypothalamic binding site to correlate well with the published pharmacology of the 5-ht7 receptor (r = 0.921). The treatment of rats with fluoxetine (5 mg/kg/day, orally) for 21 days caused a significant reduction in the number of hypothalamic 5-ht7 receptor binding sites. These data suggest that the 5-ht7 receptor binding site is expressed in rat hypothalamus and that this receptor binding site is down-regulated after a chronic increase in the synaptic level of 5-HT.

Animals↗
PubMed1993

[The vasopressin-, oxytocin- and corticoliberin-synthesizing structures of the hypothalamus in rats with diabetes mellitus under hypoxic exposures].

Hypothalamic mechanisms of neurohormone regulation of endocrine pancreas in diabetes mellitus, adaptation to hypoxia and their combination were studied on Wistar rats. To evaluate the condition of supraoptic nucleus (SON) secretory function, paraventricular subnuclei (PVH) of hypothalamus and endocrine pancreas, we used radioimmunoassay, immunocytochemical, morphometrical and histochemical methods. Hyperglycemia, hypoinsulinemia, glucagon and somatostatin synthesis and secretion intensification in diabetes mellitus is accompanied by marked reorganization of hypothalamic neurohormones (CRF, vasopressin, oxytocin) secretion with corresponding signs of activity increase of synthesizing their hypothalamus nuclei and subnuclei and also ACTH, corticosterone, cortisol rise in blood. Adaptation to hypoxia caused hypoglycemia, activated insulin biosynthesis, changed glucagon and somatostatin synthesis and secretion. CRF concentration, corticosterone and cortisol, ACTH in blood was not changed, vasopressin concentration lowered, oxytocin in median eminence of hypothalamus increased to a higher degree than in diabetes. Adaptation to hypoxia corrected impaired hormone balance and state of Langerhans islets (beta-cells destruction process inhibition, insulin biosynthesis stimulation, glucagon and somatostatin secretion decrease) in diabetes mellitus, hypothalamic neurohormones participating in this process.

Adaptation, Physiological↗