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Anterior Hypothalamic Area (anterior + hypothalamic_area)
Selected AbstractsCircadian rhythm of aromatic l -amino acid decarboxylase in the rat suprachiasmatic nucleus: gene expression and decarboxylating activity in clock oscillating cellsGENES TO CELLS, Issue 5 2002Yoshiki Ishida Background: Aromatic l -amino acid decarboxylase (AADC) is the enzyme responsible for the decarboxylation step in both the catecholamine and indoleamine synthetic pathways. In the brain, however, a group of AADC containing neurones is found outside the classical monoaminergic cell groups. Since such non-monoaminergic AADC is expressed abundantly in the suprachiasmatic nucleus (SCN), the mammalian circadian centre, we characterized the role of AADC in circadian oscillation. Results : AADC gene expression was observed in neurones of the dorsomedial subdivision of the SCN and its dorsal continuant in the anterior hypothalamic area. These AADC neurones could uptake exogenously applied L-DOPA and formed dopamine. AADC was co-expressed with vasopressin and the clock gene Per1 in the neurones of the SCN. Circadian gene expression of AADC was observed with a peak at subjective day and a trough at subjective night. The circadian rhythm of AADC enzyme activity in the SCN reflects the expression of the gene. Conclusions: Non-monoaminergic AADC in the SCN is expressed in clock oscillating cells, and the decarboxylating activity of master clock cells are under the control of the circadian rhythm. [source] Sex Differences in the Distribution and Abundance of Androgen Receptor mRNA-Containing Cells in the Preoptic Area and Hypothalamus of the Ram and EweJOURNAL OF NEUROENDOCRINOLOGY, Issue 12 2004C. J. Scott Abstract Rams and ewes show a negative-feedback response to peripheral treatment with testosterone, with both sexes having a similar degree of suppression in luteinizing hormone (LH) secretion during the breeding season. At least part of the action of testosterone to suppress gonadotropin-releasing hormone/LH secretion is exerted via interaction with an androgen receptor. The distribution of androgen receptor-containing cells in the hypothalamus has been described for the ram, but similar studies have not been performed in the ewe. In the present study, we tested the hypothesis that levels of androgen receptor mRNA expression in the preoptic area and hypothalamus would be similar in rams and ewes. Perfusion-fixed brain tissue was obtained from adult Romney Marsh ewes (luteal phase) and rams during the breeding season (n = 4/sex). Androgen receptor mRNA expression was quantified in hypothalamic sections by in situ hybridization using an 35S-labelled riboprobe and image analysis. Hybridizing cells were found in the medial preoptic area, bed nucleus of the stria terminalis, anterior hypothalamic area, ventromedial nucleus, arcuate nucleus and premamillary nucleus. The level of androgen receptor mRNA expression was higher in rams than ewes in the rostral preoptic area, caudal preoptic area and rostral portion of the bed nucleus of the stria terminalis, with no sex difference in other regions. The preoptic area and bed nucleus of the stria terminalis are important for reproductive behaviour and the sex differences in androgen receptor mRNA expression at these levels may relate to this. The high level of androgen receptor mRNA expression in the basal hypothalamus, with no sex difference, is consistent with the role of this region in the regulation of gonadotropin secretion. [source] EFFECTS OF MELATONIN ON BLOOD PRESSURE IN STRESS-INDUCED HYPERTENSION IN RATSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 10 2008Chun-Mei Xia SUMMARY 1Melatonin, acting through its receptors, is involved in numerous physiological processes, including blood pressure (BP) regulation. In present study, the effect of melatonin inhibition on stress-induced hypertension was investigated. 2The hypertensive model consisted of male Sprague-Dawley rats subjected to electrical foot-shock combined with noise. Microinjection of melatonin (0.1 and 1.0 mmol/L) into the anterior hypothalamic area (AHA) produced a fall in BP in nomortensive rats and stress-induced hypertensive rats (SIHR). Luzindole (10 mmol/L), a competitive antagonist of melatonin MT1 and MT2 receptors, almost completely abolished the depressor effect of melatonin, the MT2 receptor-specific antagonist 4-phenyl-2-propionamidotetralin (10 mmol/L) partially blocked (by approximately 60%) the depressor effect of melatonin, whereas the MT3 receptor-selective antagonist prazosin (10 mmol/L) failed to antagonize the effects of melatonin. 3Brain microdialysis was performed in the AHA and the rostral ventrolateral medulla (RVLM). Melatonin and amino acids in the dialysate samples collected were detected by high-performance liquid chromatography combined with fluorescence detection. The results indicated that melatonin concentrations in the AHA were reduced in SIHR. Microinjection of melatonin into the AHA decreased glutamate release and increased GABA and taurine release in the RVLM, which were paralleled by a decrease in arterial pressure. 4The mRNA expression of MT2 in the AHA of SIHR was higher than that in normotensive control rats, whereas there was no significant difference in MT1 mRNA expressin between the two groups. 5The results of the present study suggest that both a decrease of melatonin and an increase in the MT2 receptor in the AHA are involved in the manifestation of stress-induced hypertension. Both MT1 and MT2 receptors participated in the antihypertensive effect of melatonin in the AHA. The antihypertensive effect of melatonin was related to the decreases in the excitatory amino acid glutamate and increases in the inhibitory amino acids taurine and GABA in the RVLM. [source] ROLE OF HYPOTHALAMIC ,2 -ADRENOCEPTOR ACTIVITY IN FRUCTOSE-INDUCED HYPERTENSIONCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 10 2006Marcos A Mayer SUMMARY 1The aim of the present study was to investigate the effects of the ,2 -adrenoceptor antagonist yohimbine on blood pressure and heart rate (HR) regulation, as well as on adrenergic and serotoninergic neurotransmission, in fructose hypertensive (F) rats. 2The anterior hypothalamic area of control (C) and F rats was perfused with Ringer's solution containing 10 and 100 µg/mL yohimbine through a microdialysis concentric probe. The effects of yohimbine on mean arterial pressure (MAP) and HR, as well as on hypothalamic dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole acetic acid (5-HIAA) levels, were measured according to perfusion time. 3Although intrahypothalamic perfusion of yohimbine increased blood pressure in C rats (,MAP 9 ± 1 and 11 ± 2 mmHg for 10 and 100 µg/mL yohimbine, respectively; P < 0.05 vs Ringer's perfusion), the ,-adrenoceptor antagonist did not modify MAP in F. Intrahypothalamic yohimbine had no effect on HR at either concentration tested. Intrahypothalamic perfusion of 10 and 100 µg/mL yohimbine increased DOPAC levels in C rats (135 ± 6 and 130 ± 5% of basal levels, respectively; both n = 6; P < 0.05 vs Ringer's perfusion), but not in F animals (115 ± 6 and 102 ± 6% of basal levels, respectively; both n = 6). In both C and F rats, yohimbine administration induced an increase in 5-HIAA dialysate levels. 4The results of the present study support the notion that ,2 -adrenoceptor tone of the anterior hypothalamus of normotensive rats, which contributes to normal blood pressure regulation, is not involved in the control of HR in either normotensive C or hypertensive F rats. The absence of changes in MAP after yohimbine perfusion in F rats suggests that the ,2 -adrenoceptor tone could be decreased in this group of rats and that this may be responsible for the maintenance of hypertension in this model. Intrahypothalamic perfusion of yohimbine increased DOPAC in the dialysate only in C rats, suggesting changes in presynaptic ,2 -adrenoceptor activity in fructose-overloaded rats. Conversely, increased 5-HIAA levels did not differ between C and F groups. [source] | ||||||||||