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PubMed1980

Reversed effect of chlorpromazine on hypothalamic serotonin levels of rats with complete deafferentation of the medial basal hypothalamus.

The effect of chlorpromazine (CPZ) treatment, the complete deafferentation of the medial basal hypothalamus (MBH) and their combination on 5-HT, DA and NE levels of the MBH, hypothalamic structures outside the MBH (RH), mesencephalon and amygdala were studied. Monoamines were determined by fluorimetry. CPZ reduced 5-HT in the hypothalamus (MBH, RH), DA in the amygdala and NE concentration in the RH. Complete deafferentation of the MBH decreased 5-HT in the MBH, DA in the amygdala and NE in the hypothalamus. CPZ + deafferentation of the MBH increased 5-HT concentrations in the hypothalamus (MBH and RH) and mesencephalon, and depressed DA levels in the amygdala and NE in the hypothalamus. The data suggest that the interruption of the neural connections of the MBH results in an inverse response of the hypothalamic serotoninergic elements to CPZ.

Afferent Pathways↗
PubMed1995

GABA neurotransmission in the hypothalamus: developmental reversal from Ca2+ elevating to depressing.

GABA is the primary inhibitory transmitter of the adult hypothalamus, synthesized by many neurons and found in 50% of the presynaptic boutons. GABA causes a decrease in Ca2+ in mature hypothalamic neurons in vitro by depressing cellular activity through opening Cl- channels. Despite the early expression of GABAA receptors in the embryonic hypothalamus (E15), the cellular function of GABA in the developing hypothalamus has received little attention. In the present study the role of GABA in modulating intracellular Ca2+ in developing hypothalamic neurons was studied with fura-2 digital imaging. GABA (0.5-500 microM) applied to embryonic hypothalamic neurons elicited a dramatic and rapid increase in intracellular Ca2+ This Ca2+ rise could be completely blocked by the GABAA antagonist bicuculline (20 microM) and persisted in the presence of tetrodotoxin (1 microM). The Ca2+ elevation induced by GABA was greater than that of equimolar concentrations of the excitatory transmitter glutamate in early development. The number of E15 neurons that responded to GABA with a Ca2+ rise increased during the first few days of culture, reaching 78% after 4 d in vitro. The Ca2+ rise was 87% blocked by cadmium (100 microM) and 85% blocked by nimodipine (1 microM), indicating that the mechanism of Ca2+ increase was primarily via L-type voltage operated Ca2+ channels. Addition of bicuculline to synaptically coupled cultures caused a significant decrease in Ca2+ 4-10 d after culturing, indicating hypothalamic neurons were secreting GABA at an early age of development, and that sufficient GABA was released to elicit an increase in Ca2+. This effect was seen even after blocking all glutamatergic activity with glutamate receptor antagonists. In contrast, GABA elicited no Ca2+ rise in older neurons (> 18 d in vitro), and the action of bicuculline reversed and caused a large increase in Ca2+ in spontaneously active neurons. Similar findings were obtained in cultures enriched in GABAergic neurons from the suprachiasmatic nucleus. To determine if the Ca2+ stimulating role of GABA on developing neurons was restricted to the hypothalamus and a few other regions, or whether it might exist throughout the brain, we examined the Ca2+ responses in cultured olfactory bulb, cortex, medulla, striatum, thalamus, hippocampus, and colliculus. The majority (75%) of developing neurons from each region showed a Ca2+ rise in response to GABA. Together these data suggest that GABA elevates Ca2+ in developing, but not mature, neurons from the hypothalamus and all other brain regions examined.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

Prefrontal cortical projections to the hypothalamus in macaque monkeys.

The organization of projections from the macaque orbital and medial prefrontal cortex (OMPFC) to the hypothalamus and related regions of the diencephalon and midbrain was studied with retrograde and anterograde tracing techniques. Almost all of the prefrontal cortical projections to the hypothalamus arise from areas within the "medial prefrontal network," as defined previously by Carmichael and Price ([1996] J. Comp. Neurol. 371:179-207). Outside of the OMPFC, only a few neurons in the temporal pole, anterior cingulate and insular cortex project to the hypothalamus. Axons from the OMPFC also innervate the basal forebrain, zona incerta, and ventral midbrain. Within the medial prefrontal network, different regions project to distinct parts of the hypothalamus. The medial wall areas 25 and 32 send the heaviest projections to the hypothalamus; axons from these areas are especially concentrated in the anterior hypothalamic area and the ventromedial hypothalamic nucleus. Orbital areas 13a, 12o, and Iai, which are related to the medial prefrontal network, selectively innervate the lateral hypothalamic area, especially its posterior part. The cellular regions of the paraventricular, supraoptic, suprachiasmatic, arcuate, and mammillary nuclei are conspicuously devoid of cortical axons, but many axons abut the borders of these nuclei and may contact dendrites that extend from them. Areas within the orbital prefrontal network on the posterior orbital surface and agranular insula send only weak projections to the posterior lateral hypothalamic area. The rostral orbital surface does not contribute to the cortico-hypothalamic projection.

Amidines↗
PubMed1996

Immunocytochemical distribution of catecholamine-synthesizing neurons in the hypothalamus and pituitary gland of pigs: tyrosine hydroxylase and dopamine-beta-hydroxylase.

This study describes the distribution of catecholaminergic neurons in the hypothalamus and the pituitary gland of the domestic pig, Sus scrofa, an animal that is widely used as an experimental model of human physiology in addition to its worldwide agricultural importance. Hypothalamic catecholamine neurons were identified by immunocytochemical staining for the presence of the catecholamine synthesizing enzymes, tyrosine hydroxylase and dopamine-beta-hydroxylase. Tyrosine hydroxylase-immunoreactive perikarya were observed in the periventricular region throughout the extent of the third ventricle, the anterior and retrochiasmatic divisions of the supraoptic nucleus, the suprachiasmatic nucleus, the ventral and dorsolateral regions of the paraventricular nucleus and adjacent dorsal hypothalamus, the ventrolateral arcuate nucleus, and the posterior hypothalamus. Perikarya ranged from parvicellular (10-15 microns) to magnocellular (25-50 microns) and were of multiple shapes (rounded, fusiform, triangular, or multipolar) and generally had two to five processes with branched arborization. No dopamine-beta-hydroxylase immunoreactive perikarya were observed within the hypothalamus or in the adjacent basal forebrain structures. Both tyrosine hydroxylase- and dopamine-beta-hydroxylase-immunoreactive fibers and punctate varicosities were observed throughout areas containing tyrosine hydroxylase perikarya, but dopamine-beta-hydroxylase immunoreactivity was very sparse within the median eminence. Within the pituitary gland, only tyrosine hydroxylase fibers, and not dopamine-beta-hydroxylase immunoreactive fibers, were located throughout the neurohypophyseal tract and within the posterior pituitary in both pars intermedia and pars nervosa regions. Generally, the location and patterns of both catecholamine-synthesizing enzymes were similar to those reported for other mammalian species except for the absence of the A15 dorsal group and the very sparse dopamine-beta-hydroxylase immunoreactive fibers and varicosities in the median eminence in the pig. These findings provide an initial framework for elucidating behavioral and neuroendocrine species differences with regard to catecholamine neurotransmitters.

Animals↗
PubMed1984

Comparative distribution of bombesin/GRP- and substance-P-like immunoreactivities in rat hypothalamus.

Immunohistochemical localization of bombesin/gastrin-releasing peptide ( GRP )-like immunoreactivity (BN/ GRP -LI) and substance P-like immunoreactivity (SP-LI) in consecutive sections of rat hypothalamus was studied. Bombesin/ GRP -like immunoreactivity in the hypothalamus was partially characterized by gel filtration chromatography followed by radioimmunoassay. In the hypothalamus, SP-LI was more widely distributed than BN/ GRP -LI. Only the anterior and medial parvocellular parts of the nucleus paraventricularis and the nucleus suprachiasmaticus contained numerous cell bodies which exhibited BN/ GRP -LI. Neurons in these areas did not exhibit SP-LI. In contrast, cell bodies exhibiting SP-LI were numerous in the nucleus preopticus medialis and lateralis, nucleus anterior, nucleus ventromedialis and dorsomedialis, nucleus lateralis, nucleus arcuatus, and nucleus premamillaris ventralis and dorsalis. Only occasional cell bodies in these areas exhibited BN/ GRP -LI. It is concluded that the neuronal systems in the hypothalamus containing BN/ GRP -LI and SP-LI are separate, though the terminal fields in many areas overlap. Two peaks of BN/ GRP -LI were detected after gel filtration chromatography from extracts of the rat nucleus paraventricularis. The high molecular weight form coeluted with synthetic GRP (1-27), and the small molecular weight form eluted after synthetic bombesin. Thus, the endogenous BN/ GRP -LI is probably not authentic bombesin.

Animals↗
PubMed1975

Food-deprivation-induced behavioral arousal: mediation by hypothalamus and amygdala.

Electrolytic lesions of the basomedial hypothalamus eliminated food-deprivation-induced stabilimeter activity in rats that were prevented from becoming obese. Knife cuts lateral to the basomedial area (separating the medial and lateral hypothalamus) potentiated this activity, as did transections posterior to the basomedial region. Anterior transections (between anterior and medial hypothalamus), however, eliminated the effect. Lesions of the stria terminalis and amygdala likewise abolished deprivation-induced locomotor activity, but elevated ab-lib activity to a level comparable with that after deprivation in intact animals. Animals with combined basomedial-stria terminalis lesions behaved like animals with basomedial lesions. These results suggest that food-deprivation-induced locomotor activity in stabilimeter cages is due to a disinhibition of the basomedial hypothalamus by the amygdala via the stria terminalis.

Amygdala↗
PubMed1975

Electrical stimulation of the hypothalamus and luteinizing hormone secretion in Japanese quail.

Experiments were undertaken to localize those hypothalamic areas in the male quail (Coturnix coturnix japonica) where electrical stimulation would increase LH secretion. The posterior basal hypothalamus was stimulated with rectangular pulses (height 500 muA) through a bipolar electrode for 6 min, blood samples being taken for LH assay 20 min before, and 2, 10, 20 and 30 min after stimulation. The highest plasma concentration was observed in the 2 min sample. Over the next 30 min the LH level decreased to the resting concentration. The relative increase in LH level was greatest in sexually immature quail and least in photostimulated castrated birds, although the highest absolute levels were seen in the castrated quail. There were no statistical differences between the magnitude of the LH increases in sexually immature, mature and castrated quail. Various hypothalamic regions were then stimulated with a smaller current (200 muA) applied for only 2 min. A highly significant rise in LH followed stimulation of either the tuberal hypothalamus (postero-dorsal part of the infundibular nuclear complex, PD-INC), or the preoptic region (POR) while stimulation 0-5-1-5 mm away from these regions did not change LH secretion. Stimulation of the anterior basal hypothalamus, or of the suprachiasmatic area, caused a significant rise in LH concentration although this was less than that seen after stimulation of the POR. Stimulation in the POR or the PD-INC was ineffective if the tuberal hypothalamus had been deafferentated surgically some days previously. The data complement the studies in which destruction of the PD-INC or the POR by electrolytic lesions has been shown to block photoperiodically induced testicular growth and LH secretion.

Animals↗
PubMed1983

Binding of insulin by monkey and pig hypothalamus.

Membrane preparations from monkey and pig hypothalami bound [125I]insulin specifically. The binding appeared to be greater by preparations from anterior than posterior portions of the pig hypothalamus. Binding was time dependent, and its dissociation was first order with a half-time at 22 degrees C of 14 min. Desalanine insulin was as effective as native insulin in inhibiting the binding of [125I]insulin, while proinsulin was less effective and desoctapeptide insulin still less effective in accord with their biologic activities. Binding by membranes from cortex and thalamus appeared to be less than from hypothalamus. [125I]insulin was infused into an arterial split monkey brain preparation to determine if insulin that was blood borne bound specifically to the primate hypothalamus. Half the brain was perfused with [125I]insulin alone and the other half with [125I]insulin plus an excess of unlabeled insulin. Radioautography showed specific binding of insulin localized to the median eminence, infundibular nucleus, and microvessels. Thus, the monkey and pig hypothalami bind insulin with characteristics similar to those reported for known target tissues for insulin. Furthermore, insulin from the blood stream binds to specific anatomical structures in the hypothalamus of the monkey.

Animals↗
PubMed1986

3H-norepinephrine release in hypothalamus and brainstem of Dahl-salt sensitive and resistant rats in vitro.

Electrically evoked 3H-norepinephrine release was measured in slices of hypothalamus and brainstem of Dahl-salt sensitive (Dahl-S) and Dahl-salt resistant (Dahl-R) rats on both high and low sodium chloride diets. Only those Dahl-S rats fed a high sodium chloride diet became hypertensive, systolic blood pressure above 150 mmHg, although the Dahl-S rats on a low sodium diet, and Dahl-R rats fed a high sodium diet, both had blood pressures that were elevated compared to the Dahl-R rats maintained on a low sodium diet, when measured at the time of sacrifice. The Dahl-S rats on a high sodium diet also showed an enhancement in the field-stimulation induced release of 3H-norepinephrine in the posterior hypothalamus. Evoked 3H-norepinephrine release was not altered in low sodium diet Dahl-S rats or in low or high sodium salt Dahl-R rats. The stimulation induced 3H-norepinephrine release was also not different in the anterior hypothalamus or the A2 region of the nucleus tractus solitarius in either Dahl-S or Dahl-R animals on either sodium chloride diet. These results suggest that the alteration of evoked 3H-norepinephrine release, specifically in the posterior hypothalamus may play a role in the development and/or maintenance of hypertension.

Animals↗
PubMedDate not supplied

The responsiveness of D1- and D2-dopamine receptors in the striatum and hypothalamus of spontaneous and vasopressin hypertensive rats.

Low doses of apomorphine (20-50 micrograms/kg) induced an increase in the activity of an endogenous inhibitor of cAMP dependent protein Kinases (type I inhibitor) in the striatum, anterior and posterior hypothalamus of normotensive rats by stimulating D2-dopamine receptors. In contrast, high doses of the compound (2-10 mg/kg) produced a dose dependent decrease in type I inhibitor activity. In the posterior hypothalamus of vasopressin hypertensive rats and SHR the maximal increase of type I inhibitor activity was markedly higher than in normotensive animals. Moreover, apomorphine induced the increase of type I inhibitor activity in a much wider range of doses. Only as high dose of the compound as 10 mg/kg was able to decrease type I inhibitor activity. This points to a marked supersensitivity of D2 receptors and suggests the subsensitivity of D1 receptors in this brain area of hypertensive rats. In contrast, in the striatum and anterior hypothalamus of hypertensive rats the apomorphine dose response curves were similar to those in normotensive rats. Thus, it seems tha hypertension is associated with the alteration in sensitivity of D2 and D1 receptors in the posterior hypothalamus, the brain area involved in regulation of blood pressure.

Animals↗
PubMedDate not supplied

[In vitro thyroid hormone reception by the adenohypophysis and hypothalamus of male rats of different ages].

In studying the thyroid hormone binding with the water-salt extracts of the adenohypophysis and the hypothalamus of male rats after Schreiber it was shown that with ageing there occurred in the adenohypophysis a redistribution of T4 and T3 binding in the direction fo an increase of the T4/T3 coefficient, and a reduction of the relative T3 binding, the latter bordering with the significant one. Some reduction of the T4/T3 coefficient, both in comparison with the rest of the tissues under study and in age aspect, was peculiar to the posterior hypothalamus. In the rats-tumour-carriers some changes in the thyroid hormone binding (reduction of the T4/T3 index in the posterior hypothalamus and its sufficiently high values in the adenohypophysis and the anterior hypothalamus) were similar to those observed in normal and ageing rats.

Aging↗
PubMedDate not supplied

Noradrenaline turnover rate in the mediobasal and anterior hypothalamus of the rabbit.

Noradrenaline turnover rate in the mediobasal and anterior hypothalamus of the rabbit. Acta Physiol. Pol., 1977, 28 (1): 39-43. The rate of noradrenaline (NA) turnover in mediobasal hypothalamus (MBH) and anterior hypothalamus (AH) of the rabbit was estimated by steady-state isotopic method with a tritiated noradrenaline (3H-NA) as a tracer. The disappearance rate of 3H-NA both in MBH and in AH was found to be biphasic; the first rapid phase of the NA half-life of about 30 min, followed by the second phase of slower decay of the half-life of 2.4 h and 10 h for MBH and AH respectively. The results suggest an existence of more than one metabolic pool of endogenous noradrenaline in MBH and AH and indicate regional difference in the metabolism of NA stores in the hypothalamus.

Animals↗
PubMedDate not supplied

[Role of the hypothalamus in organizing the wakefulness-primary sleep cycle in the frog Rana temporaria].

New data are presented on the role of the hypothalamus in re-arrangement of tonus of the vegetative nervous system during three forms of rest of the primary sleep in the frog. Temporal organization of the cycle " awakefulness -primary sleep" depends on interaction of the anterior and posterior hypothalamus. The anterior hypothalamus is responsible for manifestation of two forms of rest of the primary sleep, i.e. diurnal resting form (P-1) which is associated with the increase in plastic tone of skeletal muscles, and the other resting form (P-3) which is associated with the decrease in muscle tonus. These forms of rest are accompanied by the predominance of parasympathetic tonus of the vegetative nervous system. The posterior hypothalamus is associated with manifestation of the resting form which includes the increase in the rigidity of muscle tonus (P-2) and transient phasic increase in the heart rate, the latter being observed at all forms of the primary sleep. Statistical treatment of the ECG revealed specific pattern of two-dimensional density of distribution of probabilities of R-R intervals for the resting forms of the primary sleep which is important for identification of different phases in the " awakefulness -primary sleep" cycle in vertebrates.

Animals↗
PubMed1977

[Response of splenic resistance and capacitance vessels to electrical stimulation of the hypothalamus and reticular formation in cats].

The effect of electrical stimulation of anterior, medial, and posterior hypothalamus and of midbrain RF on the spleen resistance and capacitance vessels was studied in 48 anesthetized cats. The stimulatin of all the structures but the anterior hypothalamus evoked constrictory responses of the resistance vessels and decreased the blood volume in the spleen. Apart from the constriction, the stimulation of the anterior hypothalamus decreased the tonus of both kinds of vessels in some cases. The highest perfusion pressure was observed during the stimulation of anterior hypothalamus while the greatest rise of venous outflow with the briefest latency was found during the stimulation of the midbrain RF.

Animals↗
PubMed1986

Wheel-running activity after kainic acid injection into lateral hypothalamus of rats.

It has not been resolved whether the permanent decrease in wheel-running activity observed after the placement of bilateral electrolytic lesions in the ventrolateral hypothalamus of rats is due to local neuronal destruction or to disruption of fibers of passage within the lateral hypothalamus. To further explore this question, the changes in wheel-running activity following injections of a kainic acid (KA) solution into the ventrolateral hypothalamus of rats were studied. As was found with electrolytic lesions, KA induced lesions in the ventrolateral hypothalamus resulted in a permanent decrease in wheel-running activity. The uptake of 3H-dopamine (3H-DA) into crude synaptosomal preparations of striatal tissue was used as an index of the amount of damage done to fibers of passage by KA. 3H-DA uptake by striatal tissue from rats injected with KA did not significantly differ from that of control rats. These data support the hypothesis that the decrease in wheel-running activity following injection of KA into the ventrolateral hypothalamus is the result of damage to intrinsic neurons.

Animals↗
PubMed1985

Electrical self-stimulation deficits in the anterior and posterior parts of the medial forebrain bundle after ibotenic acid lesion of the middle lateral hypothalamus.

The aim of the present study was to analyse the involvement of the intrinsic neurons located in the middle lateral hypothalamus in electrical self-stimulation measured with electrodes in the anterior and posterior parts of the medial forebrain bundle. In rats without hypothalamic lesions, self-stimulation rates from both anterior and posterior electrodes were similar on either side of the brain. For all rats with ibotenic acid-induced lesions in the lateral hypothalamus, self-stimulation rates were lower with electrodes in the area of the lesion, while self-stimulation on the contralateral side was normal. In rats with electrodes in the anterior hypothalamus, the lesion produced a large deficit when stimulation was applied to the anterior electrode ipsilateral to the lesion. Only three rats showed a decrease in self-stimulation with stimulation of the posterior hypothalamic electrode ipsilateral to the lesion; self-stimulation of the other three rats was normal. These results suggest that self-stimulation in the anterior part of the medial forebrain bundle is supported by long fibers originating in the middle part of the lateral hypothalamus, while self-stimulation in the posterior part of the lateral hypothalamus can be influenced by another system not involved in reward processes observed in the rostral part of the medial forebrain bundle.

Animals↗
PubMed2002

Control of serotonergic neurons in the dorsal raphe nucleus by the lateral hypothalamus.

Anatomical evidence indicates the presence of projections from the lateral hypothalamus to serotonergic (5-hydroxytryptamine, 5-HT) neurons of the dorsal raphe nucleus (DR). Using dual probe microdialysis and extracellular recordings in the DR, we show that the application of GABAergic agents in the lateral hypothalamus modulates the activity of 5-HT neurons in the DR. GABA and bicuculline or baclofen, applied in the lateral hypothalamus significantly reduced and increased, respectively, the 5-HT output in the DR. Likewise, the intrahypothalamic application of GABA and bicuculline reduced (14/20 neurons) and increased (8/12 neurons), respectively, the firing rate of 5-HT neurons in the DR. A smaller percentage of neurons, however, were excited by GABA (3/20) and inhibited by bicuculline (1/12). Application of tetrodotoxin in the lateral hypothalamus suppressed the local 5-HT output and reduced that in the DR. The 5-HT output in the DR increased transiently soon after darkness. The hypothalamic application of GABA attenuated and that of bicuculline potentiated this spontaneous change with an efficacy similar to that seen in light conditions. These results indicate that the lateral hypothalamus is involved in the control of 5-HT activity in the DR, possibly through excitatory (major) and inhibitory (minor) inputs.

Animals↗
PubMed2000

Distribution of dopamine D1 receptors in the nucleus paraventricularis of the hypothalamus in rats: an immunohistochemical study.

The present study investigated the distribution of dopamine D1 receptor protein in the nucleus paraventricularis of the hypothalamus. It was found that the nucleus paraventricularis of the hypothalamus contains a relatively large number of cells which are positive for presence of dopamine D1 receptor protein. The vast majority of dopamine D1 receptor-positive neurons was found in the magnocellular part, but they were also present in considerable quantity in the parvocellular part of this subregion of the hypothalamus. When measured by the Western blot technique, the quantity of D1 receptor protein found in the paraventricular nucleus of the hypothalamus was at the level found in the prefrontal cortex. It was also found that dopamine D1 receptor protein was present in neurons constitutively displaying phosphorylated CREB protein, i.e. neurons which are, as might be speculated, under the tonic influence of neurotransmitters whose receptors operate via cAMP and pCREB as second or third messengers. The presence of dopamine D1 receptors in the nucleus paraventricularis of the hypothalamus may suggest, at an anatomical level, that these receptors are involved in controlling the release of hormones, as well as their synthesis at the level of transcription, which is regulated by phosphorylation of CREB protein. Finally, the present immunocytochemical findings offer an anatomical substrate for the role of dopamine and its receptors of D1 subtype in the regulation of the activity of paraventricular neurons seen in the functional studies.

Animals↗