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Activity of centrally administered galanin fragments on stimulation of feeding behavior and on galanin receptor binding in the rat hypothalamus.

Synthetic fragments of galanin 1-29 were administered intraventricularly or into the paraventricular nucleus of the hypothalamus for analysis of the critical amino acid sequence necessary to stimulate feeding behavior in rats. Galanin 1-29 and galanin fragment 1-16 significantly increased feeding at doses of 6 nmol microinjected into the lateral ventricles and 1 nmol microinjected into the hypothalamus. There was no significant effect of D-TRP2 galanin 1-16 microinjected into the hypothalamus, and no significant effect of galanin fragments 1-9, 10-20, 12-29, 17-29, or 21-29 microinjected intraventricularly, on food consumption. Synthetic fragments of galanin 1-29 were assayed for displacement of 125I-galanin 1-29 binding to rat hypothalamic membranes. The efficacies of the galanin fragments in the feeding paradigm were consistent with the relative affinities of these fragments for the hypothalamic galanin receptor in equilibrium binding experiments. The first 16 N-terminal amino acids appear to contain galanin agonist activity on increasing food consumption and to bind to the galanin receptor in the rat hypothalamus.

Animals↗

[Subcellular distribution of adenosine system enzymes in the hypothalamus and hippocampus of the rat brain].

The subcellular distribution of 5'-nucleotidase and adenosine deaminase in rat brain hypothalamus and hippocampus was studied. In the hippocampus the 5'-nucleotidase activity was shown to be much higher than in the hypothalamus, while the adenosine deaminase activity, contrariwise, is nearly two times as high as that in the hypothalamus. During the analysis of subcellular distribution 5'-nucleotidase and adenosine deaminase were detected in all fractions under study, i. e., in nuclear, soluble, myelin fractions as well as in synaptic membranes, synaptosomes and "pure" mitochondria. The highest 5'-nucleotidase activity was found in the myelinic and synaptic fractions both in the hypothalamus and in the hippocampus. The highest adenosine deaminase activity was detected in the soluble fraction of the above structures. The enzyme activity in synaptic membranes and synaptosomes was nearly two times as low.

5'-Nucleotidase↗

[Effects of electrical or chemical stimulation of the prefrontal cortex on arrhythmias induced in cats by electrical stimulation of the anteromedial hypothalamus].

When the anteromedial hypothalamus is stimulated with a chronically implanted electrode in conscious cats, negative emotional behaviors such as restlessness and escape occur during stimulation and ventricular extrasystoles occur in rapid succession immediately after the end of stimulation. It has been shown in the lightly anesthetized cat that the activity of the sympathetic nervous system becomes predominant during stimulation of the anteromedial hypothalamus thereby causing the rises in blood pressure and heart rate. However, immediately after the cessation of the stimulation, this 'sympathetic dominant' state was observed to be switched to the 'parasympathetic dominant' state with falls in blood pressure and heart rate which was very frequently followed by the appearance of the ventricular extrasystoles (Poststimulus Arrhythmia: PSA). The purpose of this experiment was to examine how the electric and pharmacological stimulation of the prefrontal cortex modulate the rise in the blood pressure and heart rate and PSA caused by electric stimulation of the anteromedial hypothalamus. When the prefrontal cortex was electrically stimulated simultaneously with stimulation of the anteromedial hypothalamus in 24 lightly anesthetized cats, PSA was inhibited or facilitated or remained unchanged depending on the site of stimulation in the prefrontal cortex. When dopamine or noradrenaline was microinjected into the site of prefrontal cortex where PSA was inhibited, PSA was suppressed and this effect was blocked by microinjection of haloperidol or phenoxybenzamine, respectively. Dopamine was ineffective when injected in the site where PSA was facilitated; PSA was facilitated by microinjection of noradrenaline and this effect was inhibited by microinjection of propranolol. Although changes in blood pressure and heart rate were observed when the inhibition or facilitation of PSA was elicited by prefrontal injection of noradrenaline, no changes in cardiovascular parameters occurred when dopamine injection caused the inhibition of PSA. These results suggest (1) that activation of the dopamine receptor or alpha adrenoceptor in the prefrontal cortex is involved in the inhibition of PSA, and activation of beta adrenoceptor is concerned with facilitation of PSA and (2) that the mechanisms of dopamine receptor mediated inhibition of PSA appear to be different from those of inhibition of PSA by activation of the alpha adrenoceptor in the prefrontal cortex.

Animals↗

The effect of neonatal castration of male rats on the level of sex-hormone receptors in the hypothalamus and hypophysis of adult animals.

The concentration of oestradiol (E2) and testosterone (T) cytosolic and nuclear receptors was studied in the pituitary and hypothalamus of adult male rats gonadectomized either on the first day after birth (long-term castrates) or in adulthood (short-term castrates). Intact male rats and short-term castrates had the same levels as each other of cytosolic and nuclear oestrogen and androgen receptors in the pituitary, mediobasal hypothalamus (MBH), and preoptic anterior hypothalamus (POAH). In neonatally castrated males the number of nuclear T-binding sites in the pituitary and both areas of the hypothalamus decreased, whereas the number of nuclear E2-receptors was reduced only in the MBH. The number of E2-receptors in the POAH of such animals increased. The number of E2- and T-binding sites in the nuclear fraction of the MBH and POAH was the same in long-term castrates whether they did not receive testosterone propionate (TP) or received it from 7 days after birth until sexual maturity. Conversely, the T-receptor concentration in the hypophysis of neonatally castrated males who received TP was higher than in such animals which did not, but still lower than the level in intact adult rats; the number of hypophyseal nuclear E2-binding sites in long-term castrates which received TP was 1.5 times higher than in all the other groups of animals. The data demonstrate that in male rats sex-hormone receptors are involved in the sexual differentiation of the brain.

Animals↗

Effect of local inhibition of gamma-aminobutyric acid uptake in the dorsomedial hypothalamus on extracellular levels of gamma-aminobutyric acid and on stress-induced tachycardia: a study using microdialysis.

Previous studies involving local microinjection of drugs that interfere with gamma-aminobutyric acid (GABA)A receptor-mediated synaptic inhibition have led to the suggestion that endogenous GABA suppresses the activity of a sympatho-excitatory mechanism in the dorsomedial hypothalamus in rats. In this study, microdialysis was used to assess and to alter pharmacologically extracellular-levels of GABA within this region while simultaneously monitoring heart rate and blood pressure. In anesthetized rats, local microdialysis for 15 min with 2.5, 10 and 40 mM nipecotic acid, an inhibitor of GABA uptake, caused concentration-related increases in GABA and taurine in the extracellular space, but no significant change in heart rate or arterial pressure. Similar perfusion with 37.5, 75 and 150 mM KCl caused concentration-related increases in GABA as well as aspartate, glutamate, taurine, glycine and alanine. Only modest, variable increases in heart rate and no effect on arterial pressure were observed during the perfusions with high potassium. In conscious rats, unilateral microdialysis of the dorsomedial hypothalamus with 0.5 mM nipecotic acid for 2 to 2.5 hr before stress coupled with contralateral microinjection of muscimol (88 pmol/250 nl) 5 min before stress significantly reduced air stress-induced tachycardia; this reduction in tachycardia was associated with markedly elevated levels of GABA in dialysates collected from the dorsomedial hypothalamus. Neither treatment alone significantly influenced stress-induced increases in heart rate, although perfusion with nipecotic acid alone evoked similar elevations in extracellular GABA. These results suggest that extracellular levels of endogenous GABA in the dorsomedial hypothalamus may regulate the cardiovascular response to stress.

Amino Acids↗

Autoradiographic localization of [3H]RU 486 and [3H]progesterone in the uterus, pituitary and hypothalamus of the rat.

Twenty-one castrated oestrogen-primed Wistar rats, which were 2-months-old, were injected via the jugular vein with 100 microCi/100 g body weight of [3H]RU 486 or [3H]progesterone. Some of these received unlabelled compounds for competition studies. Samples of reproductive tract, pituitary and hypothalamus were excised after 15 min. The 4-micron frozen sections were processed for thaw-mounted autoradiography. The exposure time of the autoradiogram was approximately 6 months. After the injection of [3H]RU 486 and [3H]progesterone, the nuclear concentration of radioactivity was most distinct in muscular and stromal cells of the uterus, and the epithelial nuclei of lumina and glands showed weak labelling. Nuclear localization was also observed in muscle cells of the vagina, cervix and oviduct. After injection of [3H]progesterone, the radioactivity was found in the nuclei and cytoplasm of anterior pituitary cells and some cells showed a preferential nuclear concentration of radioactivity. The distribution of [3H]RU 486 in the anterior pituitary was more extensive than that of [3H]progesterone. In the hypothalamus, specific localization of [3H]RU 486 and [3H]progesterone existed in neurones accumulated in the preoptic nucleus, preoptic suprachiasmatic nucleus and the periventricular nucleus. No localization was found in the diaphragm. Pretreatment with RU 486, but not with dexamethasone, reduced the nuclear concentration of radioactivity of [3H]progesterone in the vagina, uterus, oviduct, pituitary and hypothalamus. The nuclear concentration of radioactivity after injection of [3H]RU 486 was also decreased by preinjection with progesterone. The autoradiographic results suggest that RU 486 and progesterone competed for the specific binding site (possibly a progesterone receptor) in the target cells at the levels of the uterus, pituitary and hypothalamus in vivo.

Animals↗

Autoradiographic localization of [3H]RU 486 and [3H]progesterone in the uterus, pituitary and hypothalamus of the rat.

Twenty-one castrated oestrogen-primed Wistar rats, which were 2-months-old, were injected via the jugular vein with 100 mu Ci/100 g body weight of [3H]RU 486 or [3H]progesterone. Some of these received unlabelled compounds for competition studies. Samples of reproductive tract, pituitary and hypothalamus were excised after 15 min. The 4-microns frozen sections were processed for thaw-mounted autoradiography. The exposure time of the autoradiogram was approximately 6 months. After the injection of [3H]RU 486 and [3H]progesterone, the nuclear concentration of radioactivity was most distinct in muscular and stromal cells of the uterus, and the epithelial nuclei of lumina and glands showed weak labelling. Nuclear localization was also observed in muscle cells of the vagina, cervix and oviduct. After injection of [3H]progesterone, the radioactivity was found in the nuclei and cytoplasm of anterior pituitary cells and some cells showed a preferential nuclear concentration of radioactivity. The distribution of [3H]RU 486 in the anterior pituitary was more extensive than that of [3H]progesterone. In the hypothalamus, specific localization of [3H]RU 486 and [3H]progesterone existed in neurones accumulated in the preoptic nucleus, preoptic suprachiasmatic nucleus and the periventricular nucleus. No localization was found in the diaphragm. Pretreatment with RU 486, but not with dexamethasone, reduced the nuclear concentration of radioactivity of [3H]progesterone in the vagina, uterus, oviduct, pituitary and hypothalamus. The nuclear concentration of radioactivity after injection of [3H]RU 486 was also decreased by preinjection with progesterone. The autoradiographic results suggest that RU 486 and progesterone competed for the specific binding site (possibly a progesterone receptor) in the target cells at the levels of the uterus, pituitary and hypothalamus in vivo.

Animals↗

Substance P in human hypothalamus.

The undecapeptide substance P (SP) is found in widely dispersed areas of the brain. Recently, in experimental animals, a role for SP as a presumptive neuromodulator of endocrine responses has been described. Part of this role appears to be expressed at the level of the hypothalamo-pituitary axis. The distribution of SP in human hypothalamus and pituitary stalk has rarely been examined. In this study the distribution of SP was determined using radio-immunoassay and immunohistochemical methods in 7 regions of hypothalamus and the pituitary stalk in 21 autopsy samples. The SP content was greatest in the pituitary stalk (16.7 +/- 2.9 ng/mg protein) and the mediobasal hypothalamus at the level of the tuber cinereum. (8.3 +/- 1.1 ng/mg protein) compared with all other regions (range 3.7 to 6.0 ng/mg protein). Histochemical studies in 7 cases showed a dense innervation of the pituitary stalk portal vessels by substance P-containing nerve terminals. The pituitary stalk, mediobasal and lateral hypothalamus had the highest number of SP-containing neuronal perikarya. The SP content was not affected by age, sex or delay from death to freezing of tissue. The distribution of SP supports the view that the peptide is a neuromodulator of hypothalamo-pituitary endocrine function in man.

Adult↗

[Development of ACTH-containing cells in the hypothalamus and hypophysis in their normal state and in protein deficiency].

In cryostate sections of the brain and hypophysis of newborn, 10- and 21-day-old rats, by means of the indirect method immunohistochemical reaction has been performed. As a primary serum rabbit antiserum against ACTH has been used. The ventromedial hypothalamus and adenohypophysis have been studied by means of light and electron microscopy. Relationship of ACTH-containing cells in the adenohypophysis in the process of the postnatal ontogenesis and protein insufficiency remains constant. Unlike the adenohypophysis, in the hypothalamus part of the ACTH-containing cells decreases with age. When the animals develop under conditions of protein insufficiency, changes in the part of the ACTH-positive cells, that are age-dependent, do not coincide with corresponding parameters in the control. In the adenohypophyseal cells the products of diaminobensidine reaction are distributed in cytoplasm of granules with a dense center 100-200 nm in the diameter. The ACTH-containing cells in the hypothalamus are presented as small neurons with an even distribution of the immunohistochemical reaction products in cytoplasm and in large granules 200-280 nm in the diameter. Since in the adenohypophysis and in the hypothalamus various dynamics on contents of ACTH-reactive cells in the postnatal ontogenesis and at protein insufficiency has been revealed, and various localization of the diaminobenzidine reaction products has been demonstrated, a conclusion is made on heterogenous nature of antigenic determinants against ACTH, situating in these structures.

Adrenocorticotropic Hormone↗

[Ca2+-dependent secretion of serotonin by the rat hypothalamus during ontogenesis].

A study was made of functional maturity of the terminal part of serotoninergic system of rat hypothalamus in perinatal period: the maturity was estimated by the ability to release serotonin. The release of specifically taken up serotonin (3H-5-OT) by the tissue of hypothalamus of 16-20-day-old rat fetuses, 8-9-day males and adult males was studied in the perfusion system. Spontaneous release of the labelled amine was recorded in the earliest studied period--on the 16th day of the prenatal period, but the response to K+ depolarization was absent at this time. For the first time the increase of the rate of 3H-5-OT release in response to depolarization was noted on the 17th day of development. In the absence of Ca2+ depolarizing stimulus produced no increase in the release of the labelled product. Similar results were obtained with perfusion of fetal hypothalamus on the 18t hand 20th days of development. In neonatal animals the release of 5-OT in response to depolarization was equal to that in adults. The data obtained point to a possible functioning of serotoninergic elements of hypothalamus in the perinatal period in rats.

Age Factors↗

Tyrosine hydroxylase immunoreactive neurons throughout the hypothalamus receive glutamate decarboxylase immunoreactive synapses: a double pre-embedding immunocytochemical study with particulate silver and HRP.

Silver-intensified gold (SIG) particles were used for light- and electron-microscopic immunocytochemical localization of neuronal antigens, and the SIG method was compared with related heavy-metal methods for the purpose of dual ultrastructural localization of neurotransmitter-related antigens. SIG immunostaining was combined with peroxidase immunostaining to allow simultaneous study of differentially labeled tyrosine hydroxylase and glutamate decarboxylase immunoreactive neurons in the medial hypothalamus. A number of electron-dense markers that might be of use in double immunostaining for light and electron microscopy were examined, either with a simple nitrocellulose dot-blot method or on Formvar-coated slot grids. Of these, silver-intensified 5 nm colloidal gold was the most effective. Silver intensification of colloidal silver and of peroxidase reaction product also showed promise for combined LM and EM double-immunolabeling studies. Since the silver-intensification procedure used here intensifies both gold and peroxidase, in experiments involving, double staining, the silver-intensified gold procedure should be used for the first antigen and nonintensified HRP for the second. Presumptive dopaminergic neurons containing the enzyme tyrosine hydroxylase were located throughout the hypothalamus with SIG immunostaining. In the same areas where frequent tyrosine hydroxylase immunoreactive neurons were found, many axons and bouton terminals were also found with antisera against GABA or against the GABA-synthesizing enzyme glutamate decarboxylase. Areas containing cells immunoreactive for tyrosine hydroxylase and stained with SIG and axons immunoreactive for glutamate decarboxylase and stained with peroxidase included the periventricular area (A14), the arcuate nucleus (A12), the dorsomedial hypothalamus/zona incerta area (A13), the posterior hypothalamus (A11), the medial paraventricular nucleus, and dorsal to the supraoptic nucleus, in addition to the preoptic area near the third ventricle and dorsally adjacent to the anterior commissure. For comparison, the SIG procedure was also used to stain dopaminergic neurons outside the hypothalamus in the substantia nigra and ventral tegmental area. Double immunocytochemical staining of two different neurotransmitter-related antigens allowed examination with both light and electron microscopy. By virtue of a large silver shell formed around the colloidal gold particle and its adsorbed immunoglobulin or protein A, cross-reactivity of the first set of immunoreagents stained with particulate silver and a second set stained with peroxidase could be reduced or eliminated.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

[Effect of beta-endorphin on catecholamine levels in the rat hypothalamus and cerebral cortex].

The present paper deals with the effect of beta-endorphin on catecholamine content in the hypothalamus and cerebral cortex of male rats. beta-endorphin was found to decrease catecholamine content in the rat brain, with the degree of reduction depending on the brain topography and the time following the peptide administration. 5 min later no changes in catecholamine content were observed either in the hypothalamus or in the cerebral cortex. 20 min later beta-endorphin induced a statistically significant fall of catecholamine concentration in the hypothalamus. A tendency towards its decrease was also observed in the cerebral cortex. 60 min later beta-endorphin produced an insignificant decrease in catecholamine level in both brain areas under study. It may be therefore suggested that beta-endorphin-induced decrease of catecholamine content in the hypothalamus and cerebral cortex represents one of the mechanisms underlying beta-endorphin stimulating action on a number of trophic functions of the hypophysis.

Animals↗

Characterization of pro-ACTH/endorphin-derived peptides in rat hypothalamus.

The proteolytic processing pattern of pro-ACTH/endorphin in rat hypothalamus is similar to the pattern in the pars intermedia; peptides the size of beta-endorphin, gamma-lipotropin (gamma-LPH), corticotropin-like intermediate lobe peptide (CLIP), alpha-melanotropin (gamma-MSH), joining peptide, and glycosylated gamma 3-MSH all represent predominant end products. Equimolar amounts of beta-endorphin-, alpha-MSH-, CLIP-, gamma-LPH-, and joining peptide-related immunoreactivity are found in hypothalamic extracts (approximately 3 pmol per hypothalamus). Although the proteolytic processing pattern in the hypothalamus is similar to that in the pars intermedia, a tissue-specific posttranslational processing pattern was detected. Ion-exchange analysis of beta-endorphin-sized immunoreactive material from hypothalamic extracts resolves three major forms, corresponding to beta-endorphin(1-31), beta-endorphin(1-27), and beta-endorphin(1-26). The alpha-N-acetylated forms of endorphin represent less than 10% of the total beta-endorphin immunoreactivity. Analyses of hypothalamic alpha-MSH-sized molecules with acetyl- and amide-directed alpha-MSH antisera suggest that hypothalamic alpha-MSH is fully amidated, but largely not alpha-N-acetylated. Fractionation by reverse-phase high-performance liquid chromatography (HPLC) confirms that greater than 85% of the alpha-MSH immunoreactivity corresponds to ACTH(1-13)NH2 or its sulfoxide, and less than 10% corresponds to alpha-MSH [alpha-N-acetyl-ACTH(1-13)NH2] or its sulfoxide. Isoelectric focusing demonstrates that 83-93% of hypothalamic CLIP is phosphorylated. Isoelectric focusing suggests that the majority of the hypothalamic gamma-LPH-sized immunoreactive material is indistinguishable from gamma-LPH synthesized by pituitary melanotropes. The minor extent of alpha-N-acetylation of alpha-MSH and beta-endorphin, the limited carboxyl-terminal proteolysis of beta-endorphin, and the extensive phosphorylation of CLIP represent major differences between the posttranslational processing patterns of pro-ACTH/endorphin in the hypothalamus and pars intermedia.

Acetylation↗

[Age-related properties of inductive synthesis of glucose-6-phosphatase, fructose-1,6-diphosphatase, tyrosine aminotransferase and tryptophan pyrrolase in hypothalamus stimulation].

In aged rats electrostimulation of hypothalamus caused less distinct induction of the enzymes in liver tissue, kidney and spleen as compared with the adult animals. The activation of the total RNA synthesis (actinomycin D and olivomycin) eliminated the alterations in the enzymatic activities, caused by the stimulation of hypothalamus. Effect of adrenalectomy and administration of ACTH suggested that the influence of the hypothalamus stimulation on induction of the enzymes studied was realized through the system hypophysis -- adrenal cortex. In the aged animals activation of adrenal cortex was less distinct when the stimulation of hypothalamus was carried out. The alterations in hypothalamic regulation of the enzyme induction could be an important mechanism in regulation of adaptive reactions in aged organisms.

Aging↗

[Changes in sexual functioning in the male rat after total or anterior deafferentation of the mediobasal hypothalamus].

After complete deafferentation of the mediobasal hypothalamus in male rats, the luteinizing hormone content increased in the blood which correlated with an increasing of testosterone secretion, weight of seminal glands and additional sexual organs. Half of the operated animals preserve copulating ability. The content of folliculo-stimulating hormone in the blood of animals after the complete deafferentation was decreased, particularly in non-copulating males. After the interior deafferentation of the mediobasal hypothalamus in the rats, the luteinizing hormone and testosterone contents in the blood did not change but the weight of seminal glands and concentration of folliculo-stimulating hormone in the blood decreased. The data obtained suggest different mechanisms of control of the luteinizing and folliculo-stimulating hormones secretion in male rats, the connection of the mediobasal hypothalamus with anterior hypothalamus and preoptic area being necessary for normal secretion of the folliculo-stimulating hormone.

Animals↗

The prenatal development of alkaline phosphatase activity in the hypothalamus of the rat.

The localization of alkaline phosphatase (E.C. 3.1.3.1.) positivity during prenatal development of the hypothalamus of the rat is described. At E12 all layers of the prosencephalon display alkaline phosphatase (AP) positivity. The AP positivity increases from dorsal to ventral. Within the hypothalamic area a second, rostro-ventral gradient exists from E14 onwards. At E18 both gradients have decreased. At E20 almost all AP positivity has disappeared from the hypothalamus, with the exception of some reaction product in the dorsal ventricular matrix of the hypothalamus. The significance of this pattern in relation to the differentiation of the hypothalamus and to the formation of hypothalamic connections is discussed. It is suggested that AP activity is related to the formation of connections.

Alkaline Phosphatase↗

[Effect of electrostimulation of the hypothalamus on protein biosynthesis in organs of adult and aged rats].

The effect of hypothalamus electrical stimulation on total protein biosynthesis was studied in skeletal muscle, heart, liver, adrenal cortex and thyroid gland of adult rats. In adult animals hypothalamus stimulation provokes a pronounced increase in 3H-leucine incorporation into total protein of all tissues, as well as into liver chromatin proteins. No significant changes were observed in protein biosynthesis when hypothalamus of old rats was stimulated. This can serve as evidence of age-related decrease in the ability of the hypothalamus to stimulate protein synthesis in peripheral tissues.

Adrenal Glands↗

[Effect of stimulation of emotiogenic zones of the rat hypothalamus on the course of pregnancy and the growth of the progeny].

The course of pregnancy and progeny development was studied in white rats with different emotional background during pregnancy. Self-stimulation of emotionally positive zones of the lateral hypothalamus and forced stimulation of emotionally negative zones of the ventral hypothalamus were taken as models of emotional states. Stimulation or self-stimulation of these structures, while causing unidirected negative effect on pregnancy and progeny, affected in different ways the speed of conditioning in viable progeny. Stimulation of emotionally negative zones of the ventromedial hypothalamus in the last third of pregnancy caused an acceleration of conditioning in the progeny. The self-stimulation of emotionally positive zones of the lateral hypothalamus failed to produce such effect.

Animals↗