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At least 1,441 records · Page 80Linked to original sources
PubMed1985

Growth hormone secretion in the fetal sheep following stereotaxic electrolytic lesioning of the fetal hypothalamus.

Stereotaxic surgery was performed on sheep fetuses at 108 to 110 days of gestation to investigate hypothalamic influences on fetal growth hormone (GH) release. In 5 fetuses the median eminence was destroyed, in 6 damage was confined to the medial basal hypothalamus without total destruction of the median eminence, 6 had misplaced lesions and 4 were sham operated controls. Destruction of the median eminence led to a marked fall in GH secretion and an abolition of pulsatile GH release. Following lesioning of the median eminence, GH values are comparable to resting levels in the infant lamb. Pituitary infarction was excluded in these fetuses both histologically and by a maintained GH response to exogenous growth hormone releasing factor. Lesions of the medial basal hypothalamus without destruction of the median eminence led to a significant but lesser fall in GH secretion and a reduction in the pulsatility of GH release. Sham operated fetuses and those with lesions misplaced outside the endocrine hypothalamus showed maintained high circulating GH concentrations with marked pulsatility of GH release. These studies demonstrate that fetal GH release is solely dependent upon hypothalamic stimulation presumably mediated by growth hormone releasing factor. There is no evidence for pituitary autonomy or for direct extrahypothalamic stimulation of the fetal somatotrope.

Animals↗
PubMed1985

[Role of the hypothalamus in regulating liver circulation].

In acute experiments on nembutal anesthetized dogs stimulation of anterior hypothalamus elicited changes in the hepatic artery blood flow, which followed those of arterial pressure; the vascular resistance remaining unchanged. The stimulation of medial and posterior hypothalamus led to decrease in flow and increase in the resistance of the hepatic artery. In most cases of hypothalamic stimulation the portal blood flow diminished, portal pressure and vascular resistance increased. The opposite reactions were observed during stimulation of sympathoinhibitory area, paraventricular and lateral hypothalamic nuclei. The conclusion is made that the hypothalamus participates in integrative and differential control of the hepatic circulation.

Animals↗
PubMed1979

[Analysis of hemodynamic reactions induced by stimulation of the hypothalamus in alert animals].

Electrical stimulation on the hypothalamus in alert cats increases the blood pressure and inhibits the baroceptor reflexes. In animals with extirpated sinocarotid and aortic nerves the pressor reactions are perversed to depressor ones at threshold stimulation of the hypothalamus. Meanwhile suprathreshold stimulation of this organ leads to emergence of depressor-pressor responses. It is suggested that inhibition of the baroceptor reflexes is one of the mechanisms of the hypertensive reaction emergence at stimulation of the hypothalamus.

Animals↗
PubMedDate not supplied

[Biogenic amines in the epiphysis and hypothalamus under normal conditions and following ovariectomy].

Melatonin content in the epiphysis, serotonin, noradrenaline, dopamine-in the hypothalamus, gonadotropins--in the hypophysis of rats was studied under normal conditions and following ovariectomy; regularly of the estral cycle phases was studied as well. Two series of experiments were conducted on 120 rats with regular estral cycles. The animals were divided into groups according to the estral cycle phase. Melatonin concentration in the epiphysis, serotonin, noradrenaline, dopamine--in the hypothalamus was subject to variations coinciding with the estral cycle phases. Serotonin, noradrenaline, and dopamine content decreased in the hypophysis of ovariectomized rats in comparison with control; melatonin content rose in the epiphysis. There was no complete extinction of the estral cycle in the course of investigation (20 days). The action of castration on the sexual cycle depended on the phase at which the rats were subjected to ovariectomy. A reverse relationship existed between the melatonin content in the epiphysis and serotonin content in the hypothalamus, this serving as one of the important factors in the regulation of the sexual function.

Animals↗
PubMed1977

[Organization of retinal and lateral geniculate body connections with the hypothalamus in cats].

In order to clarify connective relations between the optic system and activating formations, the pathways from the retina and the external geniculate body to the hypothalamus were investigated in the cat. Methods of Fink--Heimer and of I. V. Victorov were applied. The retina and the dorsal nucleus of the external geniculate body were stated to have efferent connections with the same nuclei in the anterior hypothalamus. Medial and posterior hypothalamus do not accept such connections. Retino-hypothalamic and geniculate hypothalamic pathways are demonstrated to terminate in the supraoptic and suprachiasmic nuclei. These pathways are bilateral and quantitatively equivalent.

Animals↗
PubMedDate not supplied

The effect of intraventricular 6-hydroxydopamine on the content of oxytocin and vasopressin in the hypothalamus and pituitary gland of water-deprived rats.

The effect of intraventricular 6-hydroxydopamine on the content of oxytocin and vasopressin in the hypothalamus and pituitary gland of water deprived rats. Acta Physiol. Pol., 1977, 28 (6): 497-504. Rats received one infusion of 200 microgram 6-hydroxydopamine with 25 microgram of ascorbic acid into the lateral cerebral ventricle. After 57 days some rats were deprived of water for 4, 8 or 12 days. Then, the animals were sacrificed by decapitation. Oxytocin was determined in extracts from the posterior pituitary lobe and hypothalamus by the method of Van Dongen and Hays, while the vasopressin content was determined by the method of Dekanski. It was found that 6-hydroxydopamine injection into the cerebral ventricles causes a rise in oxytocin content in the hypothalamus and prevents its fall during--4--12 days of dehydration.

Animals↗
PubMedDate not supplied

Adrenergic receptors in the hypothalamus concerned with control of arterial blood pressure: elicited by electrical and chemical stimulation.

The study was made with the help of a chemitrode placed in various areas of the hypothalamus by the stereotaxic technique, for electrical and chemical stimulation (noradrenaline or isoprenaline) before and after microinjection of respective blockers (phenoxybenzamine or practalol). The results indicated the presence of both alpha and beta-adrenoreceptors in the anterior and dorsomedial hypothalamus producing a depressor response, and, the presence of alpha adrenoreceptors in the posterior and lateral hypothalamus producing a pressor response.

Adrenergic beta-Antagonists↗
PubMed1980

[Afferent connections in the ventromedial hypothalamus of rats demonstrated by retrograde transport of horseradish peroxidase].

Projections into rat ventromedial hypothalamus were studied with retrograde transport of horseradish peroxidase (HRP). Following injection of HRP into ventromedial hypothalamus, labeled neurons were found in cortical and medial amygdaloid nuclei, ipsilateral mediodorsalis thalamus (MD), dorsal raphe nucleus, and contralateral sensorimotor cortex. Futhermore, labeled axons that connect directly amygdala with hypothalamus (DAH) also were found.

Afferent Pathways↗
PubMed1984

[Substance P in the central mechanism of the rabbit feeding response evoked by stimulation of the lateral hypothalamus].

The effects of substance P on the central mechanisms of food motivation elicited by electrical stimulation of the lateral hypothalamus were studied in chronic experiments on rabbits. Intravenous injection of substance P (30 micrograms/kg) brought about a dramatic reduction in the excitability of the "food center" in the hypothalamus, which returned to normal 45-60 minutes after injection. Higher concentrations of substance P provoked food behavior inversion up to the replacement of food motivation by avoidance behavior. Intravenous injections of substance P disturbed the relationships between the hippocamp, midbrain reticular formation and hypothalamus seen in health. This manifested in complete cessation of the inhibitory effects of the dorsal hippocamp and facilitating influences of the midbrain reticular formation on the excitability of the hypothalamic "food center". It is assumed that disorders of the central mechanisms of food motivation may arise from the effects produced by substance P directly on the central nervous system or on the brain via changes in the hormonal balance and responses of the autonomous nervous system.

Animals↗
PubMed1980

The effect of physiological doses of thyroxine on the level of cyclic adenosine-3',5'-monophosphate in pituitary and anterior hypothalamus of male rats of different age.

The levels of cAMP in the pituitary and anterior hypothalamus were determined by competitive binding to protein in male rats aged 2--2.5, 6--8 and 14--18 months. The lowest level of cAMP both in the pituitary and anterior hypothalamus (1.05 +/- 0.17 and 0.85 +/- 0.23 pM) (per mg wet weight, respectively) was found in 6--8 month-old rats. Administration of T4 (2 micrograms/100 g body weight, for 8 days) was followed by a decrease in cAMP level in the pituitary of 14--18 month-old animals, which was not the case with younger rats. The obtained results agree with the earlier observation that the threshold to homeostatic suppression in the hypothalamus-pituitary-thyroid system of rats decreases with aging. It is suggested that cAMP system contributes to the mechanism of changes in hypothalamic threshold and its pharmacological correction.

Aging↗
PubMed1981

Insulin acting as a modulator of feeding through the hypothalamus.

To understand the functional role of insulin in the control of feeding, biochemical and physiological studies were performed in the rat. 1) Insulin content in the brain was much higher than that in the blood, and was extremely variable from animal to animal. 2) Specific binding sites of insulin in the brain were most abundant in the hypothalamus and olfactory bulb. 3) Neither insulin content nor binding sites in the brain were significantly affected by peripheral insulin concentration. 4) Activity of glucoreceptor neurons in the ventromedial hypothalamus (VMH) was facilitated by simultaneous application of insulin and glucose, but inhibited by insulin alone. 5) Activity of the glucose-sensitive neurons in the lateral hypothalamus (LHA) was facilitated by insulin in a dose-dependent manner. 6) Stimulation of the ventral part of the LHA accelerated pancreatic vagal nerve activity. Stimulation of the dorsal part of the LHA and the VMH was inhibitory. 7) Pancreatic splanchnic nerve activity during LHA stimulation tended to show inhibition, but sometimes was modulated by stimulus frequency. Both inhibition and facilitation were observed in the activity in response to VMH stimulation.

Animals↗
PubMedDate not supplied

[Electrophysiological study of the functional connections of the hypothalamus with the forebrain in the tortoise Emys orbicularis].

During stimulation of the posterior hypothalamus, the evoked potentials with short latent periods, high amplitude and poor exhaustion by rhythmic stimulation were recorded in the hippocampal cortex. In the piriform cortex, the evoked potentials exhibited longer latent periods and complex configuration. Less readily the evoked potentials appeared in the neocortex, their latency being very large. During stimulation of the anterior hypothalamus, maximum activity was also localized in the hippocampal cortex. The data obtained indicate close connection between hypothalamic structures and the hippocampal cortex. The latter is presumably the main projectional area for the ascending afferentation from the hypothalamus.

Animals↗
PubMed1983

In vitro release of luteinizing hormone releasing hormone (LH-RH) from the hypothalamus in pregnant rats.

Using the superfusion system, the basal LH-RH release from the hypothalamus was investigated during pregnancy in rats. Pregnant rats were sacrificed on day 10, 15, 18 and 21 of pregnancy by decapitation. The hypothalamus was taken out as a block, and superfused with Krebs-Ringer bicarbonate buffer in conditions of 37 degrees C, 95% O2 + 5% CO2. The changes in LH-RH concentrations in the superfused medium were measured using a radioimmunoassay for LH-RH. Serum LH levels were significantly decreased from day 10 to 15, but increased rapidly from day 18 to 21. On the other hand, the release of LH-RH from the hypothalamus remained stable until day 18, followed by a significant increase on day 21. These results suggested that the decrease in LH secretion from day 10 to 15 would not be due to the changes in LH-RH release, while the increase in serum LH levels on day 21 might depend on the increase in the release of LH-RH.

Animals↗
PubMed1980

Effect of histamine H1- and H2-receptor agonists on gamma-aminobutyric acid (GABA) content in hypothalamus and striatum of the rat brain.

The intraventricular administration of histamine in a dose of 500 microgram, and two histamine H2-receptor agonists i.e. 50-250 microgram of dimaprit and 100 microgram of 4-methylhistamine decreased GABA level after 30 min (by approximately 20%) in the hypothalamus, but not in the striatum of the rat brain. The level of GABA was significantly reduced by 100 microgram of dimaprit after 2 h. Drugs selectively stimulating histamine H1-receptor (100 microgram) did not significantly change GABA concentration of the rat hypothalamus. The results suggest the existence of an H2-receptor--mediated histamine--GABA interaction in the rat hypothalamus.

Animals↗
PubMed1981

[Intermittent liberation of gonadoliberin (GnRH) by the rat hypothalamus in vitro].

Hypothalamus were dissected from suprachiasmatic area to mamillary bodies in 50 days old male rats. These fragments were subsequently removed and incubated for 3 hours at 37 degrees C in Dulbecco Modified Eagle's medium supplemented with glucose and containing calcium (1.25 mM) and potassium (5.81 mM). Incubation medium was changed every 5 or 15 minutes and immediately collected at 4 degrees C for highly specific radioimmunoassay of GnRH using R 42 antiserum of Nett and Niswender. In these conditions, mean +/- 1 SD release of immunoreactive GnRH per 1 hour was 199 +/- 68 pg (n = 4) and 135 +/- 38 pg (n = 6) in medium collected every 5 and 15 minutes respectively. Furthermore GnRH release was found to be episodic, 3 to 5 peaks being observed during a period of 2 hours. It is concluded that, following deafferentation and isolation in vitro, mature hypothalamus remains capable of releasing GnRH in a spontaneous periodic manner, suggesting that this particular feature of neuroendocrine maturation can be initiated in the hypothalamus itself.

Animals↗
PubMed1978

Mass spectrometric measurement of catecholamine turnover in rat hypothalamus after long-term L-dopa infusion.

To test the effect of L-dopa on norepinephrine turnover in rat hypothalamus, we gave steady-state, long-term (19-hour) infusions of L-dopa to conscious, restrained rats. After 19 hours, infusions were switched to identical doses of 2,5,6-trideutero-L-dopa (D3-L-dopa) and production of D3-dopamine and D3-norepinephrine was followed at intervals thereafter. Animals were sacrificed and their hypothalami were dissected and divided into left and right halves. Using gas chromatography-mass spectrometry, we measured isotopic enrichment with one side of the hypothalamus and, after the addition of deuterated internal standards, determined total concentration of dopamine and norepinephrine in the other half of the same hypothalamus. Maximal steady-state enrichment by a given dose of D3-L-dopa was determined by 19-hour infusions of D3-L-dopa alone. Results show that total dopamine production is proportional to dopa dose. Norepinephrine synthesis, on the other hand, proceeds at a constant rate that is independent of dopa dose or dopamine concentration and which is similar to the endogenous rate reported by others using tracer techniques.

Animals↗
PubMed1983

[Effect of chronic stress on the ultrastructure of the myocardium and hypothalamus of "emotional" and "nonemotional" rats].

The influence of chronic stress on the ultrastructure of the myocardium and hypothalamus was studied in experiments on male rats with different levels of emotional-behavioral reactivity. "Emotional" rats manifested a pronounced increase in glycogen granules in myocytes and intercellular space, appearance of the areas of overcontraction of myofibrils, conglomerates of aggregated platelets in myocardial capillaries, and red cell egress from myocardial and hypothalamic capillaries. Alterations in the ultrastructure of the myocardium and hypothalamus in "nonemotional" rats were less marked and consisted in the appearance of the areas of overcontraction of myofibrils, enlargement of sarcoplasmic reticulum caverns, and in an increase in the lipid content in cardiomyocytes. The ultrastructural changes in the myocardium and hypothalamus of "emotional" and "nonemotional" rats indicate different reactivity of the animals and are likely to be accounted for by different levels of activation of their adrenergic systems.

Animals↗