摘要:

Electrodes were implanted in dogs in the dorsal portion of the medulla oblongata near the obex. A week or more later, the electrodes were stimulated while changes in plasma renin activity, plasma epinephrine and norepinephrine, and blood pressure were monitored. Stimulation of 20 points in 16 dogs produced clear-cut increases in plasma renin activity. In almost all instances, these increases were associated with marked increases in blood pressure. There was also a small increase in circulating epinephrine without a significant change in plasma norepinephrine. Stimulation of the medulla 4 h after renal denervation was not associated with any increase in plasma renin activity even though the pressor response was comparable to that before denervation. The response was also absent in dogs stimulated two week after renal denervation. The data show that renin secretion can be increased in association with marked increases in blood pressure. They also show that the increase produced by stimulation of the medulla oblongata is mediated via the renal nerves.

ISSN:0028-3835    

DOI:10.1159/000121949

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

In adult male rats, sectioning of the fornix was found to abolish the diurnal variation in plasma corticosterone by raising the lowest and decreasing the highest values during the day. Operated animals in which the fornix had not been transected showed a normal pattern of diurnal fluctuation of plasma corticosterone.

ISSN:0028-3835    

DOI:10.1159/000121950

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

In connection with the possibility of hormonal influences upon norepinephrine (NE) metabolism of the central nervous system in the premenstrual tension syndrome and postpartum depression, we examined the effect of progesterone upon NE metabolism in the brain of ovariectomized rats. The comparison of progesterone-treated and untreated rats did not afford significant results. However, progesterone did exert a significant inhibitory effect upon amphetamine-induced NE catabolism. A similar but not significant effect of progesterone was found in stressed rats. The influences of progesterone upon stress-altered NE-metabolism were higher in the telencephalon than in the brain stem.

ISSN:0028-3835    

DOI:10.1159/000121951

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

Circadian periodicity of the hypothalamic content of corticotropin-releasing factor (CRF) was determined in normal and adrenalectomized male rats, using the intrapituitary micro-injection method. It was found that the CRF activity in the rat hypothalamus showed a definite circadian variation, having the peak value at 6 p.m. and the minimum at 8 a.m. under the lighting schedule used here (light between 6 a.m. and 7 p.m. followed by 11 h of darkness). A close temporal relationship with a definite phase shift was observed between the CRF activity and plasma corticosterone level. The finding thus supports the concept that the circadian rhythm of the pituitary-adrenal axis is a direct reflection of the rhythmicity of CRF activity in the median eminence. Furthermore, the persistent periodicity observed in the CRF activity in the absence of circulating corticosterone suggests that the dominating mechanism for the control of the circadian rhythm of CRF activity is of neural origin, being independent of the negative feedback mechanism.

ISSN:0028-3835    

DOI:10.1159/000121952

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

A direct effect of thyroxine (T4) on the hypothalamus has been pre-viously claimed and questioned.Using a microapplication technique, T4 was applied to the rat hypothalamus in vivo for 3 days. A significant slowing of the epithyroid disappearance rate (EDR) of 131I was observed in 37 of the 54 animals. No significant slowing was observed during the control phase when plain agar-agar tubes were in the hypothalamus or when the T4-agar microapplication tube was not applied near the paraventricular nucleus. 125I labelled T4-agar studies confirmed the absence of diffusion of T4 from the site of microapplication to the pituitary. We conclude that T4 has a direct inhibitory effect on a discrete area of the rat hypothalamus.

ISSN:0028-3835    

DOI:10.1159/000121953

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

The site at which norethindrone (NE) acts to block ovulation in the rat was investigated by electrochemical stimulation of the preoptic hypothalamus and by the administration of crude bovine median eminence (ME) extracts. Single injections of 0.5 mg NE on different days of the oestrous cycle raised the preoptic threshold for the induction of ovulation. Using 20 µA for 90 sec, there was a significant increase in the number of rats ovulating as compared with NE-treatment alone, only when NE was given on day 1 (oestrus) of the cycle. NE-treatment did not significantly affect the number of rats ovulating in response to ME extract. Compared with NE-treatment alone, NE plus ME extract increased the number of rats ovulating when the NE was given on day 1 of the cycle but not on days 2 and 3. It was concluded that NE exerts its inhibitory action on ovulation in the rat at a site within the central nervous system

ISSN:0028-3835    

DOI:10.1159/000121954

出版商:S. Karger AG    

年代:1971

数据来源: Karger

摘要:

In female rats, cuts were made with the use of the Halasz technique around the preoptic area, leaving the connections between the preoptic area and hypothalamus intact. Such cuts do not interfere with spontaneous ovulation, as opposed to cuts made at the level of the optic chiasm. In addition, the effects of cuts around the preoptic area on progesterone-induced secretion of gonadotrophins were studied. In acute experiments, these cuts blocked the activity of progesterone injected on the third day of dioestrus of the 5-day cycle or at pro-oestrus of the 4-day cycle. However, in chronic experiments, progesterone injected at pro-oestrus, followed by pentobarbital, did induce ovulation.

ISSN:0028-3835    

DOI:10.1159/000121955

出版商:S. Karger AG    

年代:1971

数据来源: Karger