Mari Hotta

Intracerebroventricular administration of corticotropin-releasing factor inducesc-fos mRNA expression in brain regions related to stress responses: comparison with pattern ofc-fos mRNA induction after stress

Centrally administered corticotropin-releasing factor (CRF) produces a number of physiological and behavioral changes akin to those elicited by exposure to acute stress. However, the specific brain site of action responsible for the centrally activating property of CRF has not been precisely determined. In this study, we used in situ hybridization histochemistry for c-fos mRNA to map potential neuronal structures activated after intracerebroventricular (i.c.v.) injection of CRF and compared the distribution of c-fos mRNA with that after stress. Wistar male rats were sacrificed 30, 60, 120 and 180 min after the i.c.v. injection of 1 microgram ovine CRF or vehicle alone. Another group of rats was exposed to immobilization stress for 60 min or electrical foot-shock stress (1.5 mA, 1-s duration, 30 x) for 15 min and sacrificed before and 30, 60, 120 and 180 min after the beginning of stress. Centrally administered CRF rapidly (30-60 min) induced c-fos mRNA expression in most of the areas that showed hybridization signals for c-fos after stress: the limbic structures, including the piriform cortex, cingulate cortex, the lateral septal nucleus, the hippocampus, the anterior corticomedial and the medial amygdaloid nuclei, the hypothalamic nuclei, such as the paraventricular nucleus, the supraoptic nucleus (SO) and the dorsomedial nucleus (DMD), and some brainstem nuclei like the pontine nucleus, the locus ceruleus (LC) and Barringtons nucleus. The granular layer of the cerebellum, some thalamic nuclei and the habenula also showed hybridization signals after i.c.v. injection of CRF and stress. However, c-fos induction in the bed nucleus of the stria terminalis, the central nucleus of the amygdala (CeA) and the nucleus tractus solitarius (SOL) was seen only after i.c.v. administration of CRF; in the septo-hypothalamic nucleus and the superior olive, however, c-fos mRNA expression was observed only after stress. There were no differences in the pattern of c-fos mRNA expression between the two stress paradigms. In contrast, i.c.v. injection of saline-induced expression of c-fos mRNA in the piriform cortex, neocortex, cingulate cortex and the amygdala was much less than that seen after i.c.v.-administered CRF as evident in the intensity of the signals. These results suggest that CRF produces c-fos mRNA expression in the brain areas related to stress response, and that CRF may induce behavioral and neuroendocrine responses through activating these brain structures, such as the limbic system and the hypothalamic nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)

Involvement of corticotropin-releasing factor in restraint stress-induced anorexia and reversion of the anorexia by somatostatin in the rat

The mechanism by which restraint stress induces suppression of food intake and the influence of intracerebroventricular (icv) administration of somatostatin on the anorexia induced by restraint stress were examined in the rat. Ninety minutes of restraint stress reduced food intake of rats to approximately 60% that of control. Anorexia induced by 90 min restraint stress was partially reversed by icv administration of alpha-helical CRF (9-41), a corticotropin-releasing factor (CRF) antagonist, and completely reversed by anti-CRF gamma-globulin. These results provide further evidence in support of the theory that CRF is involved in the inhibitory mechanism of food intake in restraint stress. ICV administration of somatostatin 14 and SMS 201-995, an analog of somatostatin, also reversed restraint stress-induced anorexia. It is, therefore, suggested that somatostatin may counteract the suppressive action of CRF on food intake in stress.

Corticotropin-releasing factor receptor type 1 mediates emotional stress-induced inhibition of food intake and behavioral changes in rats

We investigated whether corticotropin-releasing factor (CRF) receptor type 1 (CRFR1) is involved in emotional stress-induced inhibition of food intake and behavioral changes in rats. The inhibition of food intake and increase in locomotor activity induced by emotional stress using a communication box were reversed by both intracerebroventricular injection of alpha-helical CRF (9-41), a non-selective CRF receptor antagonist, and intraperitoneal injection of a selective non-peptidic CRFR1 antagonist. These results suggest that CRFR1 mediates at least in part the emotional stress-induced inhibition of feeding behavior and increase in locomotor activity.

In vitro release of growth hormone-releasing factor from rat hypothalamus: effect of insulin-like growth factor-1

The release of growth hormone-releasing factor (GHRF) from rat hypothalamus was investigated in vitro. After 60 min preincubation the released GHRF from sliced rat hypothalamic fragments during 60 min incubation was detected by a highly specific and sensitive radioimmunoassay for rat GHRF. The release of GHRF was Ca2+-dependent and enhanced by high concentration of K+. Insulin-like growth factor-1 (IGF-1) significantly decreased GHRF release to 65% and 84% of the control at concentrations of 10(-8) M and 10(-7) M, respectively. These results suggest that this in vitro system is useful for the investigation of the mechanism of GHRF release from the hypothalamus and that IGF-1 is probably involved in the feedback inhibition of growth hormone secretion by attenuating GHRF release from the hypothalamus besides countering the effect of GHRF on the pituitary.

The effects of chronic central administration of corticortrop in-releasing factor on food intake, body weight, and hypothalamic-pituitary-adrenocortical hormones

The effects of chronic central administration of corticotropin-releasing factor (CRF) on food intake, body weight, and hypothalamic-pituitary-adrenocortical hormones were investigated in rats. The infusion of ovine CRF at doses of 0.3 and 1.0 microgram/h continuously induced decrease in food intake and a suppression of body-weight gain for 7 days. The inhibition of body weight gain induced by CRF could not be accounted for solely by a decreased food intake since the suppression of body-weight gain in CRF-infused rats was significantly greater than that observed in rats which received the same amount of food as the CRF-infused rats. The content of proopiomelanocortin (POMC) -derived peptides in the anterior lobe of the pituitary as well as the plasma levels of ACTH and corticosterone (B) were significantly elevated in CRF-treated rats, and the CRF content in the hypothalamus was significantly decreased. These results suggest that chronic intracerebroventricular (icv) administration of CRF stimulates the synthesis and secretion of POMC-related peptides in the pituitary and suppresses food intake accompanied by inhibition of body weight gain. The results are similar to clinical and laboratory findings observed in patients with stress-induced anorexia.

Inhibins and activins

Publisher Summary This chapter discusses the isolation, structure, characterization, and biosynthesis of inhibins and activins. The two pituitary gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) which regulate the development and maturation of the gonad, are identified. The ability to quantitate FSH and LH in serum revives the inhibin concept, which offers an explanation for the differential regulation of FSH and LH release often observed in humans and experimental animals. Inhibin activity is monitored by an in vitro bioassay using rat anterior pituitary cells in monolayer culture. The message encoding each of the subunits of the inhibins is cloned from porcine and bovine ovarian complementary DNA (cDNA) libraries. DNA sequence analysis shows that the inhibin a subunit is initially synthesized as a large precursor protein with potential N-linked glycosylation sites. The two β subunits are also found to be derived from large polypeptide precursors and cleavage at the processing sites to yield the mature β subunits at the carboxy termini of the precursors. Using the porcine cDNAs as hybridization probes, the human and murine inhibin subunit precursors are also cloned and sequenced.

The satiety effect of growth hormone-releasing factor in rats

The effect of growth hormone-releasing factor (GRF) on feeding behavior in rats was examined. Starvation-induced feeding was suppressed by intraventricular administration of 1 nmol and 4 nmol of synthetic human GRF (hGRF). Food intake was not affected when the peptide was administered by intraperitoneal injection. Furthermore, centrally administered hGRF also suppressed feeding in hypophysectomized rats. These results suggest that GRF suppression of food intake is mediated through the central nervous system independent of its effect on pituitary growth hormone secretion.

Psychological stress increases arousal through brain corticotropin-releasing hormone without significant increase in adrenocorticotropin and catecholamine secretion

The effect of psychological and psychophysical stress on pentobarbital (PbNa)-induced sleeping time was examined in rats to clarify the influence of psychological stress on arousal. Psychological stress and electric footshock of 5-60 min duration significantly shortened PbNa-induced sleeping time, and the shortening was reversed by intracerebroventricular administration of a corticotropin-releasing hormone (CRH)-receptor antagonist. Electrical footshock and restraint significantly raised plasma adrenocorticotropin (ACTH) and catecholamine levels, whereas psychological stress did not significantly affect the plasma hormones levels. These results suggest that both psychological and psychophysical stress increase arousal through brain CRH. It is also concluded that expression of the central nervous system action of CRH, such as increasing arousal, is not necessarily accompanied by a significant increase in the secretion of ACTH and catecholamine in psychological stress.

Brain corticotropin-releasing hormone increases arousal in stress

The effect of restraint stress on pentobarbital-induced sleeping time was examined in rats. Restraint for 60 and 75 min significantly shortened pentobarbital-induced sleeping time. The shortening of sleeping time by restraint was completely reversed by intracerebroventricular (i.c.v.) administration of alpha-helical CRH(9-41), a corticotropin-releasing hormone (CRH) receptor antagonist. In conjunction with our previous finding that i.c.v. administration of CRH shortens pentobarbital-induced sleeping time, the results suggest that restraint stress increases arousal through brain CRH.

Effect of human growth hormone-releasing hormone on GH secretion in Cushing's syndrome and non-endocrine disease patients treated with glucocorticoids.

The GH response to 100 micrograms human growth hormone-releasing hormone (hGRH) given intravenously was evaluated in eleven patients with Cushings syndrome who had been ill for more than one year and in six patients with non-endocrine diseases who were treated with glucocorticoid for one to twelve weeks. Extremely low to no response of plasma GH to hGRH injection was noted in all seven patients with Cushings disease and in four patients with Cushings syndrome due to an adrenal adenoma or carcinoma. In contrast, all six patients with non-endocrine diseases who were treated with glucocorticoid showed normal GH responses to hGRH. These results suggest that the diminished hGRH-induced GH secretion in patients with Cushings syndrome might be caused by the prolonged period of hypercortisolemia.