摘要:

A decrease in estrous cycle duration, due to shortening of the period of vaginal closure (VC), has been observed in female guinea pigs exposed to the odor of urine from males of the same species. VC shortening was also observed in females exposed to the odor of female urine collected during the period of vaginal opening (VO). No alteration in VC duration occurred, however, in females exposed to urine collected in the 1st 7 days of VC. Also VC shortening did not occur in bulbectomized females exposed to the odor of male urine. Therefore, it was concluded that guinea pig urine, when highly concentrated, contains pheromones capable of shortening estrous cycle VC.

ISSN:0028-3835    

DOI:10.1159/000122474

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

To evaluate a possible role of histamine in the CNS control of prolactin and gonadotropin release, adult ovariectomized rats, with stainless steel cannulae implanted in the 3rd ventricle, were given s.c. injections of 10 µg of estradiol benzoate. 48 h later, 2 µl of 0.9% NaCl alone or of saline containing 1, 5, 25 or 125 µg of histamine dihydrochloride was microinjected into the ventricle. Immediately before and then 15, 30 and 60 min after, blood samples were withdrawn from etherized rats for radioimmunoassay (RIA) of serum prolactin, LH and FSH. In the histamine-injected rats, an increase in prolactin titers was observed and was highly significant in groups receiving the higher doses. A small yet significant release of LH, but not of FSH, was also observed. When 25 µg of histamine was injected directly into the pituitary or into the jugular vein, no elevations were observed, indicating a site of action in the brain. Restraint stress elevated serum prolactin and lowered serum LH and FSH in ovariectomized rats. These responses were blocked by the intrajugular injection of diphenhydramine (5 mg/kg). It is suggested that histamine may be involved in the hypothalamic control of prolactin release and possibly of gonadotropin rele

ISSN:0028-3835    

DOI:10.1159/000122475

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The dose-response effects of apomorphine and ET-495 (piribedil), 2 specific dopamine (DA) receptor stimulators, and haloperidol, a DA receptor blocker, were tested on the secretion of prolactin (PRL), thyroid stimulating hormone (TSH), growth hormone (GH) and luteinizing hormone (LH) in male rats. Both apomorphine and piribedil reduced serum PRL and TSH levels, stimulated GH release at low but not at high doses and either had no effect or tended to reduce serum LH levels. The minimal effective dose of apomorphine for reducing PRL by 30 min was 0.01 mg/kg; TSH inhibition was observed with a dose of 0.1–0.3 mg/kg. The inhibitory effects of apomorphine (1.0 mg/kg) on PRL and TSH levels were maximal by 15 min and diminished by 120 min; plasma GH was highest 120 min after injection. Thyroidectomy (10 days) markedly elevated serum TSH, had no effect on serum PRL and inhibited the ability of apomorphine (0.1 or 0.3 mg/kg) to reduce TSH but not PRL levels. These observations may indicate that separate dopaminergic control mechanisms exist for TSH and PRL secretion. Administration of haloperidol elevated serum PRL, tended to lower TSH, dramatically reduced GH and had no effect on LH levels. Haloperidol pre-treatment blocked the effects of apomorphine on PRL, TSH and GH secretion. The overall results of this study indicate that DA agonists inhibit PRL and TSH, stimulate GH but do not stimulate LH release in male rat

ISSN:0028-3835    

DOI:10.1159/000122476

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The accumulation of 3H-testosterone and its metabolites in the brain of neonatal and prepubertal rats was measured following injections of the hormone in vivo, or after incubation of minced brain tissue with 3H-testosterone in tissue culture medium. Radioactivity associated with purified nuclei and various cytoplasmic fractions of brain tissue was determined in 2–5-day, 10–12-day, and 25–32-day-old animals. Comparisons of radioactive steroids, accumulated 2 h after s.c. injections of 3H-testosterone or 3H-estradiol, showed that testosterone (T) is accumulated to a lesser extent than estradiol (E), but the age-related patterns of uptake are similar for both steroids. A continuous decrease in radioactivity was observed in nuclear and cytoplasmic fractions from the brains of 2-, 4-, and 12-day-old animals that were given injections of 3H-testosterone in vivo. This age-related pattern of decreasing uptake of radioactivity was not observed when excised brain tissue was incubated with 3H-testosterone in tissue culture medium. Thus, it appears that the age-related responsiveness of neonatal rats to T may be due more to the fact that decreasing amounts of the hormone reach the brain in older animals than that an inherent difference exists in tissue susceptibility during this period. Most of the radioactivity accumulated in the brain was associated with cytoplasmic fractions. Less than 1% of the homogenate radioactivity accumulated in purified nuclei. This restricted uptake and the kinetics of 3H-testosterone nuclear accumulation suggest that a nuclear site of action of T and/or its metabolites exists in the neonatal rat

ISSN:0028-3835    

DOI:10.1159/000122477

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Preovulatory LH surges were measured in cannulated proestrous rats. Such LH peaks were also obtained by infusing pentobarbital-blocked animals with LH-RH for periods of up to 20 h; this suggested that the pituitary LH stores were exhausted. However, the total amount of LH secreted appeared more or less determined by the LH-RH dose, indicating that the size of the releasable LH pool is not fixed.

ISSN:0028-3835    

DOI:10.1159/000122478

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

82% of female mice, that had received a single injection of 50 µg testosterone propionate (TP) at 4 days of age, became persistent estrous by 90 days. If 50 µg pentobarbital or 10 µg reserpine was given simultaneously with TP, the incidence of hypothalamic masculinizatîon (persistent estrus (PE) and polyfoUicular ovaries lacking corpora lutea) at 90 days dropped to 33 and 30%, respectively. Phenoxybenzamine (50 µg) also decreased the incidence of PE to 20 and 30% at 60 and 90 days of age, respectively. However, propranolol failed to nullify the masculinizatîon caused by TP. These results seem to suggest that a monoaminergic mechanism is involved in the hypothalamic masculinizatîon of neonata

ISSN:0028-3835    

DOI:10.1159/000122479

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The puberty-controlling function of the mediocortical amygdala in immature female rats was investigated by lesioning this region at different ages and by studying the effects on the onset of spontaneous and experimentally-induced precocious puberty. At 21 days of age, bilateral lesions in the anterior mediocortical amygdala (AMCA) caused precocious puberty and enhanced the puberty-accelerating effect of bilateral lesions produced simultaneously in the medial preoptic area (MPA). Similar lesions, ineffective on day 26, delayed the onset of puberty when produced on day 32 in otherwise untreated rats. Lesions in the posterior mediocortical amygdala (PMCA) at 26 or 32 days of age postponed puberty in untreated rats and inhibited the advancement of their 1st pubertal ovulation that resulted from damage to the ventromedial-arcuate region (VAH) or daily administration of 0.05 µg estradiol benzoate (EB) per 100 g b.w. The results confirm earlier findings of different gonadotropin-controlling activities of the AMCA and PMCA in immature female rats and suggest maturational changes in the function of both areas. The gonadotropin-inhibiting action exerted by the AMCA at 3 weeks of age is lost when puberty approaches; a gonadotropin-stimulating activity seems to develop in both the AMCA and PMCA

ISSN:0028-3835    

DOI:10.1159/000122480

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Saline and luteinizing hormone-releasing hormone (LRH) were infused into the medial preoptic area (MPOA), arcuate nucleus (ARC), lateral hypothalamic area (LHA) and the cerebral cortex (CC), and the effects on sexual behavior were studied in estrone- (E-) primed ovariectomized (OVX) female rats. Each cannulated, OVX female known to be sexually active was primed with E in doses too low to initiate consistent mating behavior. LRH infusion in either the MPOA or ARC facilitated sexual behavior as measured by the lordosis-to-mount (L/M) ratio; LRH infusion in the LHA or CC, as well as saline infusion in all neural sites, was ineffective in initiating comparable behavior patterns. The results concur with findings utilizing systemic LRH injections and support the notion that LRH may act directly on neural tissue to potentiate lordosis behavior in the female rat.

ISSN:0028-3835    

DOI:10.1159/000122481

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Monoaminergic influences on the regulation of the hypothalamo-hypophyseal-adrenocortical (HHA) system during acute stresses (hypoxia and hypercapnia) were investigated in male rats. Plasma corticosterone levels were used to assess HHA activity, and the alterations in monoaminergic activity were induced by pretreating the animals with various pharmacologic agents (reserpine, αMT, FLA-63, pCPA, L-Dopa, pargyline, Lilly 110140, phentolamine and propranolol). Dexamethasone-treated rats were utilized to assess the site at which these monoaminergic substances acted. The latter experiments showed that these agents did not have a marked effect directly on the adrenal cortex and thus the site(s) of action was at the level of the anterior pituitary and/or above. Altering the serotoninergic system did not appreciably influence the HHA response to hypoxia and hypercapnia, whereas increasing the activity of the adrenergic system partially prevented the rise usually observed in plasma corticosterone levels during these stresses. These data suggest that different aminergic pathways may be utilized for different stresses

ISSN:0028-3835    

DOI:10.1159/000122482

出版商:S. Karger AG    

年代:1976

数据来源: Karger