摘要:

To study the eyes’ role in maintaining the circadian rhythm in pituitary-adrenal function, 24-h patterns of corticosterone levels were compared in intact and blinded adult female rats. Rats were blinded by optic enucleation at approximately 80 days of age. Nonstress plasma corticosterone levels were determined fluorometrically in serial blood samples obtained from a tail vein at 4-h intervals for 44-h periods, 3 and 10 weeks after surgery. At 3 weeks after surgery, blinded and intact rats demonstrated comparable rhythms in corticosterone levels. At 10 weeks, steroid fluctuations in individual blinded rats still had an approximate 24-h periodicity. However, these fluctuations were no longer synchronized with the light-dark cycle or with those of other rats. These findings suggest that rats blinded as adults have a free-running pituitary-adrenal circadian rhyth

ISSN:0028-3835    

DOI:10.1159/000122495

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Plasma and hypothalamic LHRH was measured by specific radioimmunoassay in intact and ovariectomized rats, and the values were correlated with peripheral plasma (PP) FSH and LH titers. At most stages of the estrous cycle, plasma LHRH was either undetectabie or present at very minimal values. An increase in PP LHRH concentration was observed in some animals between 13.00 and 20.00 h on proestrus. The mean elevation in LHRH was greatest in rats when blood samples were taken by decapitation; elevation was somewhat less when samples were taken from etherized rats and minimal when taken from rats bearing indwelling jugular cannulae. LHRH was elevated in approximately half the ovariectomized animals; repeated samples were drawn at 15-min intervals from intrajugular cannulae. In animals with LHRH elevations, LHRH was highly variable, which indicates that it is released in pulsatile fashion. Plasma LHRH and LH titers were correlated in ovariectomized animals. The relatively low correlation between LHRH and LH may be explained by the fact that a pulse of LHRH can elicit LH release over a considerable time span; also, LHRH is cleared much more rapidly from the circulation than is LH, as revealed by the time course of disappearance of exogenous LHRH given by bolus injection. In intact rats, hypothalamic LHRH content was slightly lower at 10.00 h on diestrus day 1 than at other sample times. LHRH was significantly lower 4 weeks following ovariectomy compared to levels in intact rats at any sample time. It would appear that LHRH’s resynthesis does not keep pace with its release in ovariectomized rats, resulting in a decline in hypothalamic store

ISSN:0028-3835    

DOI:10.1159/000122496

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Since noradrenergic neurons in the brain appear to inhibit ACTH secretion and dopamine-β-hydroxylase (DBH) is found in noradrenergic neurons, the effect of variations in pituitary-adrenal activity on the activity of DBH in the brain stem, hypothalamus and hippocampus was determined. There was no significant circadian fluctuation in hypothalamic or brain stem DBH, as measured by the coupled radioenzymatic method of Molinoff et al. [1971]. Pentobarbital and ether anesthesia, injection stress and surgical stress also had no acute effect. There was a decrease in anterior hypothalamic DBH 30 min after immobilization stress. Two days after adrenalectomy, there was a decrease in DBH in the hypothalamus and brain stem. A large dose of corticosterone (B) caused an increase in hypothalamic DBH. However, a smaller dose of B which increased plasma B to values comparable to those produced by endogenous secretion failed to have this effect. The data demonstrate an effect of the adrenal glands on brain DBH activity, but it is as yet uncertain whether this effect is mediated by glucocorticoids

ISSN:0028-3835    

DOI:10.1159/000122497

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Tissue distribution of radioactivity was studied at 2,4 and 6 h after intravenous injection of 3H-estradiol-17β (41.7 ng/100 g b.w.) in 12 light-sterilized and 11 control female rats ovariectomized 72 h prior to injection. Female rats were light-sterilized by exposure to continuous illumination for 82 days and, based on the duration of continuous vaginal cornification and the absence of corpora lutea at post-mortem histological examination of the ovaries, were anovulatory for at least 30 days prior to injection. Control rats were housed under conditions similar to the experimentals except that they were exposed to alternating lighting (14 h light: 10 h dark). They remained ovulatory throughout the experiment. Uterine 3H-estradiol uptake and retention were significantly depressed in the light-sterilized group. There were no significant differences in 3H-estradiol uptake or retention as a result of light-sterilization in any of the other tissues studied, including anterior, middle, and posterior hypothalamus, hippocampus, amygdala, cerebrum, anterior pituitary and plasma. The failure to detect a reduction in neural 3H-estradiol uptake demonstrates that the anovulatory state can exist without a concomitant reduction in the hypothalamic estrogen binding capacity. The possibility is discussed that the decreased target tissue binding noted in various types of anovulatory animals is the result, not the cause, of altered ovarian function

ISSN:0028-3835    

DOI:10.1159/000122498

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Lordosis was elicited in 49% of 87 hormonally untreated, hypophysectomized-ovariectomized (hypox-ovx) female rats in response to palpation of the flanks and perineum (vaginal stimulation was not applied). By contrast, only 12% of 113 hormonally untreated ovariectomized (ovx) rats showed lordosis in response to such stimulation. Subsequently, hypox-ovx and ovx-only rats were given daily injections of 1 µg/kg estradiol benzoate (EB) and tested for sexual receptivity with males. The estrogen-treated hypox-ovx females became sexually receptive significantly earlier, and exhibited higher lordosis quotients and more soliciting behavior, than the estrogen-treated ovx-only rats. The increased sexual responsiveness in the hypox-ovx rats could be due to increased LRH activity. To test this, we treated hypox-ovx rats with dihydrotestosterone propionate (DHT-P), which suppresses plasma LH levels but is relatively ineffective in inducing sexual receptivity, and found a significant depression of lordosis responsiveness. These experiments suggest that hypox-ovx females show a heightened responsiveness to hormonal and/or sensory factors that induce a lordosis response, possibly because of increased LRH activity

ISSN:0028-3835    

DOI:10.1159/000122499

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

To further evaluate the influence that sex, time of day and/or stage of the estrous cycle have on stress-induced changes in gonadotropin secretory patterns, rats were subjected to acute ether stress and subsequently sacrificed at 1.5, 3, 5, 10 and 15-min intervals. A significant change in FSH levels was not detectable, however serum LH levels consistently showed a transient elevation, and prolactin release occurred rapidly and in large increments in every case. Variation in basal hormone levels due to sex, circadian rhythmicity, or estrous cyclicity did not alter the pattern of the response of individual hormones to the stress but did markedly influence the magnitude of the response.

ISSN:0028-3835    

DOI:10.1159/000122500

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Heparinized blood samples were obtained through an indwelling catheter in the central ear artery from sexually mature female New Zealand white rabbits after copulation. Immediately after 1 or 2 matings the female was transferred to a restraining cage; blood samples were taken at intervals while the animal was completely immobilized for 3–5 h or was only immobilized for blood withdrawal. Ovulation was detected by the presence of corpora lutea at laparotomy the following day. Plasma was analyzed for LH by established radioimmunoassay procedures. Immobilization did not inhibit ovulation or the pre-ovulatory surge of LH in either group. These data suggest that immobilization cannot inhibit the reflex release of LH in the female rabbi

ISSN:0028-3835    

DOI:10.1159/000122501

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The metabolism of testosterone (T) in neonatal rat brains was measured following in vivo and in vitro incubations with 3H-testosterone. Steroids associated with nuclear and cytoplasmic fractions of brain tissue from 4, 12, and 32-day-old male and female rats were identified. Although there are quantitative differences under different methods of incubation, in all cases more than 95% of the radioactivity was recovered and identified as T, or the 5α-reduced metabolites, DHT and 3α-androstanediol. Most of the metabolism of T occurred in the cytoplasm, but 5α-reduced metabolites were also associated with purified nuclei. Reaction kinetics indicate that the metabolic sequence is T → DHT → 3α DIOL. DHT levels were similar in the cytoplasmic fractions from the neonates (4 and 12-day-old animals) and prepubertal animals (32-day-old animals), but 3α-androstanediol was significantly reduced in these fractions from prepubertal animals compared to those from neonates. Sex differences in the metabolism of T in the various subcellular fractions were not de

ISSN:0028-3835    

DOI:10.1159/000122502

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122503

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122504

出版商:S. Karger AG    

年代:1976

数据来源: Karger