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PubMed1977

Role of the posterior hypothalamus in the development of acute brain swelling.

Destructive stereotaxic lesions were made in the posterior hypothalamus, unilaterally or bilaterally, in 26 dogs. In 21 dogs the intracranial pressure (ICP) was maintained in normal range, and in five dogs the ICP was artificially elevated to 300 to 400 mm h2o, preceding the procedures to the hypothlamus. Arterial oxygen and carbon dioxide pressure ((PaO2 and PaCO2) were maintained in the normal range. Before and after each procedure, systemic arterial pressure (SAP) was elevated by intravenous injection of norepinephrine (5 X 10(-3) mg/kg) to determined whether the ICP increases coincidentally with elevation of the systemic arterial pressure. The intracranial pressure/mean arterial pressure ratio of elevation by injection of norepinephrine was not significant regardless of the level of the ICP, or of uni-or bilateral lesions of the hypothalamus. The authors conclude that dysfunction of posterior hypothalamus does not play a specific role in the development of vasomotor paralysis leading to acute brain swelling, under conditons of normal or moderately raised ICP with normal PaCO2 and Pato2 levels.

Animals↗
PubMed2002

Leptin regulates growth hormone-releasing factor, somatostatin, and alpha-melanocyte-stimulating hormone but not neuropeptide Y release in rat hypothalamus in vivo: relation with growth hormone secretion.

It is known that leptin, an adipocyte-derived hormone, exerts a stimulatory effect on growth hormone (GH) secretion in various animal species. However, no previous study examined in vivo whether leptin affects the secretion of GH-releasing factor (GRF), somatostatin (SRIH), and some other closely relevant neurohormones in the hypothalamus. Therefore, in this study we investigated the effects of direct leptin infusion into the hypothalamus on the in vivo release of GRF, SRIH, alpha-melanocyte-stimulating hormone (alpha-MSH), and neuropeptide Y (NPY) in freely moving adult male rats using the push-pull perfusion. Leptin was infused into the median eminence-arcuate nucleus complex at three different concentrations, i.e., 1.0 (normal feeding level), 3.0, and 10 ng/ml (mild obesity level). In normally fed rats, only 10 ng/ml leptin was able to stimulate GH secretion, whereas in 3 d fasted rats, GH release was dose-dependently stimulated by 1.0 and 3.0 ng/ml leptin, although its 10 ng/ml dose did not produce additional effects. The facilitation of GH secretion occurred as increased pulse amplitudes without significant changes in the pulse frequency. During the leptin infusion, the hypothalamic GRF increased and SRIH decreased in magnitudes that approximately paralleled those of GH changes. Leptin stimulated the release of alpha-MSH in the fasted but not fed rats. It is likely that the fasting-induced increase in the hypothalamic alpha-MSH sensitivity to leptin is relevant to ingestive behavior involving leptin. Leptin was without effect on NPY release in either the fed or fasted group. Although it is certain that NPY mediates at least part of the metabolic actions of leptin, NPY is unlikely to be involved in the acute effects of leptin on GH, GRF, and SRIH secretion. These results demonstrate for the first time that leptin can alter the in vivo release of both GRF and SRIH in rat hypothalamus concurrently with the stimulation of GH secretion.

Animals↗
PubMed1975

[Participation of the posterior hypothalamus in the activity of the ascending activating system].

In chronic experiments on cats with premezencaphalic section of the brain stem electrica stimulation of the posterior hypothalamus caused desynchronization of the electrical activity of the neocortex. After the isolated injury of the posterior hypothalamus a moderate electrical stimulation of the medical part of the midbrain reticular formation failed to cause any pronounced activation of the neocortex. The results obtained indicated an important role of the posterior hypothalamus in the function of the ascending activating system.

Animals↗
PubMed1985

Ontogeny of neuropeptidergic systems: luteinizing hormone releasing hormone (LHRH); somatostatin (SRIF) and neurophysin (NF) in the hypothalamus of the domestic pig by immunocytochemistry.

The ontogenic development of some hypothalamic neuropeptides: luteinizing hormone releasing hormone (LHRH); somatostatin (SRIF) and neurophysin (NF) and their localization in the hypothalamus of fetuses in different stages of the fetal life were studied by immunoperoxidase method. It was found that differentiation of the neurons which produce the examined hormones begins in the midstage of pregnancy. LHRH is stored in the nerve terminals of the median eminence (ME) and organum vasculosum of the lamina terminalis (OVLT) since 72 day of gestation and its amount gradually increases with the development of the embryo. In this stage a few immunoreactive (ir) LHRH perikarya appear but they are most numerous in the last days of pregnancy (110 day). They are localized in the most anterior periventricular parts of the hypothalamus, area preoptica, diagonal band of Broca and very rare in the medial-basal hypothalamus. Somatostatin is produced in the separate neuronal system and appears in the last days of fetal life. Neurophysin is present in both magnocellular nuclei in 72 day-old fetuses, but at the end of gestation it is seen also in some preoptico-septal region.

Animals↗
PubMed1988

[Dynamics of the neuronal activity of the posterior hypothalamus during a phase shift of the wakefulness-sleep cycle].

Dynamics of neuronal activity of the posterior hypothalamus in the sleep-wakefulness cycle was studied in free moving cats using mobile metal microelectrodes. Computer analysis and statistical treatment of the data have shown that the majority of neurons (89.3%) in the above-mentioned area discharge with high frequency during active wakefulness and emotional stage of paradoxical sleep; the frequency of discharges decreases during passive wakefulness and nonemotional stage of paradoxical sleep and is the lowest in the slow wave sleep though it has been higher than at the other states. Comparatively small number of neurons (3.6%) show opposite dynamics of the activity. They fire more intensely during slow wave sleep and the frequency of discharges decreases during active wakefulness and paradoxical sleep. In posterior hypothalamus some neurons (7.1%) are found which fire intensely during active wakefulness as compared with slow wave sleep and paradoxical sleep. The neurophysiological mechanisms for regulation of the sleep-wakefulness cycle and the involvement of posterior hypothalamus in this process are discussed.

Action Potentials↗
PubMed1986

[Effect of phosphatidylcholine on the body temperature and activity of posterior hypothalamus neurons in animals].

The experiments on rats and rabbits have shown that exogenous phosphatidyl choline (PC) was capable of altering the body temperature and bioelectrical activity of posterior hypothalamus neurons following intravenous and intracerebroventricular administration. Intracerebroventricular PC was more effective in raising the body temperature of rats. The experiments on rabbits have demonstrated that the influence of PC (intravenous administration) on the body temperature depended on the initial body temperature. In rabbits, the changes in the impulse activity of certain non-thermosensitive posterior hypothalamus neurons induced by intracerebroventricular PC administration were found to be dependent on the initial firing rates. PC inhibited the increase in bioelectrical activity of thermosensitive neurons in posterior hypothalamus caused by the rise in the brain temperature secondary to body temperature elevation.

Animals↗
PubMed1985

Gudden's tegmental nuclei and their connections to the hypothalamus and the reticular formation. I. An experimental study using retrograde labelling with HRP or iron-dextran in the rat.

31 rats were studied for the retrograde transport of HRP or dextran-fer from the corpus mamillare, anterior hypothalamus or reticular formation to the cells of the ventral (VG) and dorsal (DG) Gudden's tegmental nuclei. Judging by the position of the projection cells the VG was found divisible into the peripheral and central parts, a finding out of line with the conventional cytoarchitectonic division. The two parts differ in part of their projections. While both project jointly to the medial mamillary body, the peripheral part has a separate projection to the whole lateral hypothalamus whereas the central part projects also to the RF (ncl. pedunculopontinus and ncl. pontis oralis). The group of cells localized close to the cranial field of the VG, cytoarchitectonically referred to as the pars compacta ncl. centralis superioris, has the same projections as the external parts of the VG and can, therefore, be seen as a component of the VG peripheral part like the cells over the caudal field of the VG (pars intrafascucularis localized already among FLM fibres). The central part is made up of cells localized in the middle portions of the bulk of the VG cells. The dorsal Gudden's tegmental nucleus projects its ventral part to the lateral mamillary body, to the medial and lateral hypothalamus and to the RF (ncl. pontis oralis). The dorsal part of the DG projects solely to the RF (ncl. pontis oralis).

Animals↗
PubMedDate not supplied

[Monoaminergic structures of the hypothalamus in chronic stress].

Falk's histochemical fluorescent method was used to study monoamine (MA)-containing structures in isolated hypothalamus nuclei and in the neurohemal region of the medial eminence (ME) in 40 male rats under the conditions of a long-term stress (6 months) which was caused by a repeated weak electrodermal stimulation. A statistically significant decrease in the intensity of MA fluorescence in the early period of the experiment, particularly significant in the fibers of the paraventricular nucleus and in the ME, was replaced by an increase in the intensity of MA fluorescence in the fibers and perikaryons in the arcuate paraventricular nuclei and in the ME on the 100th day. On the 180th day of the experiment MA fluorescence in the hypothalamus structures of the experimental and control rats did not differ significantly. Thus MA in the hypothalamus nuclei and ME were involved in adaptation processes of the body to chronic stress action. Changes of the MA content were particularly marked in the paraventricular nucleus, associated with cortical RH and vasopressin production as well as in the arcuate nucleus and in the ME associated with the entry of these hormones in the hypophysial portal vessels to regulate ACTH secretion.

Animals↗
PubMed1979

[Role of adreno- and cholinoreactive structures of the hypothalamus in regulating blood coagulation and maintaining it in a fluid state].

Electrical stimulation of anterior and lateral hypothalamus as well as acetylcholin injection into the same areas activated the anticoagulating blood system whereas adrenaline injections activated the coagulating system. The electrical stimulation with certain parameters seems to involve cholinoreactive structures of the hypothalamus, shifting the blood potential towards hypocoagulation. The sitmulation of the paraventricular and ventromedial hypothalamic nuclei with the same current activated the blood coagulating system whereas stimulation of the preoptic lateral or medial areas, medial supraoptic nucleus of the hypothalamus induced no changes in the homeostatic system. The data obtained suggest that the regulation of the blood anticoagulating system involves the anterior hypothalamic area, the suprachiazmatic nucleus, and the rostral part of the lateral hypothalamic area.

Acetylcholine↗
PubMed1978

Localization of inhibitory mechanisms to aggressiveness in the medial hypothalamus.

Release of aggressive reactions was studied by placing a small lesion on the medial hypothalamus in the rat with previous massive destruction on the contralateral side of the hypothalamus. A set of tests for reactivity to provocations was applied to rats before the operation, after the unilateral lesion, and once more after the bilateral lesions. Bilateral lesions were accomplished in 53 rats. None of them increased food intake even though the ventromedial region was involved in many cases. Only 7 developed signs of aggressiveness. The unique histological feature of the animals showing aggressiveness was that the lesions were confined to the posterior hypothalamus usually sparing the ventromedial nucleus and were close to the base. It was suggested that the lesions might have interrupted the fibers projecting to the midbrain mechanisms for control of emotional reactivity.

Aggression↗
PubMed1980

The morphology of the diencephalon in the Prosimii. II. The Lemuroidea and Lorisoidea. Part II. Epithalamus, subthalamus and hypothalamus.

This study (Part II) deals with the comparative structure of the epithalamus, subthalamus and hypothalamus. The same prosimian species used in the study of the thalamus and metathalamus (Part I) are used here. The epithalamus does not show any remarkable change in the phylogeny of the prosimian diencephalon. In the subthalamus, the nucleus subthalamicus enlarges progressively in size, and shows a very close relationship to the zona incerta, the fields of Forel and the pregeniculate body. The zona incerta is observed to consist of two parts the ventral part relating to the nucleus subthalamicus and the dorsal part ot the nucleus reticularis. The fields of Forel is well differentiated into fields H1 and H2. The hypothalamus is described here having four regions--preoptic, suraoptic, infundibular and mamillary. The preoptic and supraoptic regions appear to be indivisible in all prosimian species, for the constituent nuclei of both regions extend rostrally and caudally in the anterior part of the hypothalamus. The nucleus supraopticus is evidently complicated in structure, as it appears not only to have two separate parts, but also an isthmus that connects these parts. This interlinking strand of cells is termed not the nucleus supraopticus diffuses but the nucleus/area commissuralis postopticus. The nucleus paraventricularis is a massive nucleus, and appears to have a non-neurosecretory part and a neurosecretory part. An interesting feature has been observed in certain prisimian species such as Galago demidovii, Lepilemur and Loris gracilis, the nucleus paraventricularis accessorius which may be regarded as an erratic derivative of either nucleus paraventricularis or nucleus supraopticus. The nucleus tuberalis lateralis makes its first definitive appearance in the Prosimii. The nucleus ventromedialis hypothalami appears to be larger and more clearly defined than the nucleus dorsomedialis hypothalami. From the latter nucleus, a cellular condensation has been observed to stretch lateralwards--nucleus dorsolateralis hypothalami. The hypothalamic areas--anterior, dorsal, lateral and posterior--are not very much different among the prosimian species, although the anterior and posterior hypothalamic areas appear to have more attributes of a nucleus than an area. The mamillary region is very well developed in all prosimian species. The medial mamillary nucleus is clearly divided into several parts. The nucleus mamillaris lateralis is poorly developed, but can be identified lying between the lateral part of the medial mamillary nucleus and the nucleus intercalatus. In regard to the latter nucleus, there is some topographical confusion, but the nucleus intercalatus is easily identified as the bed nucleus of the supramamillary commissure.

Animals↗
PubMedDate not supplied

[Response of neurons of the ventro- and dorsomedial nuclei of the hypothalamus to biologically heterogeneous stimuli].

Unit activity in ventro- and dorsomedial hypothalamic nuclei recorded extracellulary in nonanaesthetized rabbits was evoked by acoustic clicks or electrocutaneous nociceptive and innocuous stimuli. The majority of units of the dorsomedial hypothalamus was inhibited by nociceptive stimulation and was excited by innocuous one. In contrast, units in the ventro-medial hypothalamus reduced their discharges in response to innocuous stimuli and augmented them in response to nociceptive stimuli. Latency of inhibition of units in the dorsomedial hypothalamus was shorter than that of excitation. It is concluded that the hypothalamic non-nociceptive system is activated by innocuous stimuli and inhibited by nociceptive stimulation.

Animals↗
PubMedDate not supplied

[Pharmacologic analysis of monoaminergic mechanisms of the medial hypothalamus in food-getting conditioned reflexes in rats].

In the study of food-procuring conditioned reflex in rats it was found that microinjection of noradrenaline and dopamine in the medial hypothalamus impedes its realization, prolonging the reflex latency, lowering its value and the number of conditioned food-procuring movements. The effects of catecholamines on food-procuring conditioned activity are specific and effectuated correspondingly via alpha-adrenoreceptors or receptors of the hypothalamic neurones sensitive to haloperidol and aminazine. Local administration of GABA to the hypothalamus prolongs the latency of the food-procuring conditioned reflex, but does not change its value and the number of conditioned food-procuring movements. The effect of GABA is not due to the effect on adreno- and dopamine receptors of the hypothalamus.

Animals↗
PubMedDate not supplied

[Participation of the hypothalamus in regulating the activity of rat liver energy metabolism enzymes].

In soluble fraction of rat liver studies have been made on the activity of glycolytic enzymes and dehydrogenases of the pentose phosphate pathway 3 and 20 hours after the electrical stimulation of the medial (HVM) and lateral (AHL) structures of the medial hypothalamus via chronically implanted electrodes. Electrical stimulation of the HVM within 3 hours decreased total hexokinase, glucose-6-phosphate dehydrogenase, and lactate dehydrogenase activities, and to a lower extent -- the activity of glucokinase. This effect was not prevented by the adrenalectomy. During stimulation of the AHL, the decrease of LDH activity was the same, whereas the activity of hexokinase, glucose-6-phosphate dehydrogenase and glucokinase decreased to a lower extent. Electrical stimulation of the medial hypothalamus within 20 hours decreased the response, this effect being presumably associated with the decrease in the content of endogenous noradrenalin in the liver of animals. The role of the hypothalamus and sympathetic nervous system in regulation of the investigated enzymes of energy metabolism in the liver is discussed.

Adrenalectomy↗
PubMed1999

Nitric oxide synthase in the guinea pig preoptic area and hypothalamus: distribution, effect of estrogen, and colocalization with progesterone receptor.

Nitric oxide (NO) may function as an intercellular messenger in the hypothalamus and may play a role in the control of gonadotropin-releasing hormone (GnRH) secretion and sexual behavior. Progesterone also plays an important role in the regulation of reproductive functions. Recent experiments have shown that progesterone-induced sexual behavior in ovariectomized, estrogen-primed rats was caused by the release of NO from nitric oxide synthase (NOS)-containing neurons and the subsequent stimulation of the release of GnRH. To provide further neuroanatomical support for the role of NO in these gonadal steroid-dependent behavioral and physiological processes, we determined (1) the distribution of the nicotinamide-adenosine-dinucleotide phosphate-diaphorase (NADPHd) and NOS enzymes in the guinea pig preoptic area and hypothalamus, regions that contain steroid receptors; (2) the effect of estrogen on NADPHd activity in these regions; and (3) the neuroanatomical relationship between NOS and the progesterone receptor (PR). For this purpose, single-(NADPHd) and double- (NADPHd with NOS or NADPHd with PR or NOS with PR) staining techniques were applied to sections of brains of guinea pigs. The studies showed scattered NADPHd-positive neurons in most parts of the preoptic area and heavily stained cells in the hypothalamus. In these regions, the pattern and density of NOS immunoreactivity closely corresponded to the pattern of NADPHd staining. Quantitative analysis showed an increase in the number of NADPHd-positive neurons in the ventrolateral nucleus of ovariectomized animals primed with estradiol. Approximately 16% of the NOS-immunoreactive (IR) cells in the rostral preoptic area and 55% of NOS-IR cells in the ventrolateral nucleus displayed PR immunoreactivity. These results suggest that NOS may be regulated by gonadal steroids and provide neuroanatomical evidence that progesterone may exert its effect directly on more than half of NOS-synthesizing cells in the ventrolateral nucleus, a key region in the control of sexual behavior.

Animals↗
PubMed2000

Topographical organization of projections from the subiculum to the hypothalamus in the rat.

The projections from the subiculum to the hypothalamus were comprehensively examined in the rat by using the anterograde Phaseolus vulgaris leucoagglutinin (PHA-L) and retrograde cholera toxin B subunit (CTb) methods. Tracing of efferents with PHA-L indicated that the medial preoptic region received projection fibers from the temporal two-thirds of the subiculum, whereas the anterior, tuberal, and mammillary regions received those from the full longitudinal extent of the subiculum. The subicular projections to the anterior and tuberal hypothalamic regions were also found to be organized in a topographical manner such that the temporal-to-septal axis of origin in the subiculum determined a ventromedial-to-dorsolateral axis of termination in the medial zone of the hypothalamus: Massive labeled fibers from the temporalmost part of the subiculum terminated in the subparaventricular zone and its caudal continuum around the dorsal and medial aspects of the ventromedial nucleus, and those from progressively more septal parts terminated in progressively more dorsolateral parts of the medial zone. In addition, the temporal-to-septal axis of origin in the subiculum tended to determine a medial-to-lateral axis of termination in the preoptic region as well as a ventral-to-dorsal axis of termination in the mammillary region. Furthermore, the temporal-to-septal axis of origin in the septal two-thirds of the subiculum corresponded to a ventrolateral-to-dorsomedial axis of termination in the medial mammillary nucleus. The topographical projections from the subiculum to the medial zone of the hypothalamus were confirmed by CTb experiments, representatively in the subicular projections to the anterior hypothalamic region. These results suggest that different populations of neurons existing along the longitudinal axis of the subiculum may exert their influences on the execution of different hypothalamic functions.

Animals↗
PubMed2000

Acute effects of L-tryptophan on tryptophan hydroxylation rate in brain regions (hypothalamus and medulla) of rainbow trout (Oncorhynchus mykiss).

Levels of 5-hydroxytryptophan (5-HTP) in brain regions (hypopthalamus and medulla) of rainbow trout were analysed by HPLC-EC 0, 10, 30, and 40 min after intraperitoneal administration of different doses of L-tryptophan (Trp) (0, 12.5, and 25 mg. kg(-1) body weight) in fish treated with 3-hydroxybenzylhydrazine (NSD1015; 75 mg. kg(-1)). The results show that, in control fish, 5-HTP levels in hypothalamus (58.03 +/- 6.36 pg. mg(-1) brain tissue) were significantly higher than those observed in medulla (28.04 +/- 4.32 pg. mg(-1) brain tissue). Basal tryptophan hydroxylation rates (after 0 mg. kg(-1) Trp administration) were 0.42 +/- 0.07 pg 5-HTP. mg(-1). min(-1), and 0.63 +/- 0.24 pg 5HTP. mg(-1). min(-1), for hypothalamus and medulla respectively. On the other hand, the results demonstrate that L-tryptophan administration induced significant increases in the rate of tryptophan hydroxylation, both in hypothalamus and medulla. These findings indicate that, in a way similar to that observed in mammals, brain tryptophan hydroxylase is unsaturated by its substrate (tryptophan) under normal physiological conditions. J. Exp. Zool. 286:131-135, 2000.

5-Hydroxytryptophan↗
PubMed1997

Desipramine modulates 3H-ouabain binding in rat hypothalamus.

We have previously shown that Na+, K(+)-ATPase activity in hypothalamus is increased after administration of an acute dose of desipramine, a noradrenaline uptake inhibitor (Viola et al., Cell Molec Neurobiol 9:263-271, 1989). In this report the same treatment (10 mg per kg) was applied to evaluate 3H-ouabain binding in rat brain sections by quantitative autoradiography. Results disclosed an increase in the number of ouabain binding sites in hypothalamus but not in cerebral cortex. Concomitantly, such acute DMI treatment enhanced K(+)-stimulated-p-nitrophenylphosphatase activity in hypothalamus membranes whereas it failed to modify cerebral cortex membranes. A direct interaction of DMI with the enzyme was ruled out since in vitro DMI is known to inhibit the enzyme. It may be speculated that DMI indirectly stimulates Na+, K(+)-ATPase through the increase in noradrenaline which acts in turn on the external phosphorylated site of the enzyme.

4-Nitrophenylphosphatase↗