摘要:

Electrolytic lesions of the hypothalamic medial forebrain bundle (MFB) produced substantial deficits in the copulatory behavior of male rats, but no changes in testicular, seminal vesicle, ventral prostate or penis weights. Radioimmunoassay of serum from lesioned and control animals revealed a small but statistically insignificant reduction in testosterone and LH levels, and no change in FSH levels of lesioned males. In a second experiment, androgen levels were maintained in castrated males by subcutaneous implants of silastic capsules containing crystalline testosterone; this procedure failed to prevent the copulatory deficit which accompanied subsequent MFB lesions. We have concluded that the behavioral deficit produced by such lesions is not a direct result of pituitary-gonadal dysfunction.

ISSN:0028-3835    

DOI:10.1159/000122355

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Female Sprague-Dawley-derived rats were injected at 25 days of age (pre-pubertal) or 60 days of age (adult) with 1 µg dexamethasone/100 g b.w. either before the beginning of the daily rise in serum corticosterone (at 10.00 or l2.OOh in adults and 10.00 h in prepubertal rats) or after the daily rise had begun (at 14.00 h in adults, and 12.00 or 14.00 h in prepubertal rats). Blood samples were collected by decapitation at 16.00, 20.00 and 24.00 h on that day and 04.00, 08.00 and 16.00 h the following day. In adults, dexamethasone (DEX) given at 10.00 shifted the corticosterone (B) peak to 20.00 from the control peak at 16.00 h. DEX at 12.00 or 14.00 h shifted the peak to 04.00. In prepubertal rats, DEX given before the B rise did not shift the subsequent peak and the pattern of B did not diverge from controls. DEX given at 12.00 or 14.00 shifted the peak to 24.00 h. At 08.00 the next day, B was depressed in adults but normal in prepubertal rats. At 16.00 h, both age groups showed depressed B in comparison to controls. Prepubertal rats appear to respond differently to dexamethasone than do adults

ISSN:0028-3835    

DOI:10.1159/000122356

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The effects of ovariectomy on the ultrastructure of neurons within the SCH nuclei of the rabbit were investigated. All SCH neurons of the intact controls were similar in that they showed no morphological evidence of enhanced neurosecretory activity. In contrast, two distinct types of neurons were present within the SCH nuclei of the ovariectomized animals. The small, Type I neurons were ultrastructurally identical to the SCH neurons of the intact controls. The larger, Type II neurons, on the other hand, clearly presented structural evidence for elevated intraneuronal synthesis. To ensure that the changes which characterized the Type II neurons were due, at least in part, to the removal of ovarian steroids following ovariectomy and not to surgical stress alone, the SCH nuclei of laparotomized rabbits were also studied. Although the same two neuron types were observed, the number of Type II neurons in the laparotomized controls was significantly smaller (p < 0.001) than the number in the ovariectomized group. These findings suggest that Type II neurons probably represent a functional state of the smaller, non-active neurons of the intact controls. In addition, the ultrastructural features that distinguish Type II neurons are positively related to the endocrine state of the rabbit and, therefore, may represent the hypothalamic synthesis of the releasing hormones that control its gonadotropic activity.

ISSN:0028-3835    

DOI:10.1159/000122357

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The influence of decapitation or encephalectomy (total removal of the brain leaving the pituitary in place) on the adrenal corticosterone concentration of the 20-day-old rat fetus has been studied in normal pregnant rats, in adrenalectomized pregnant rats, and in adrenalectomized pregnant rats subjected to the stress conditions of inhalation of ether for 40 min. Decapitation or encephalectomy of the fetus always results in a drop in adrenal corticosterone concentration within 4 h which is prevented in 15 min by injecting 3.2 mU of hog ACTH into the decapitated fetus. In mothers adrenalectomized in order to avoid a negative feedback reaction of maternal corticosteroids on the fetal pituitary-adrenal system, ether inhalation causes an important rise in adrenal corticosterone concentration in normal fetuses but not in decapitated or encephalectomized ones. Thus ether, which crosses the placental barrier, is a stressor agent for the fetal rat.

ISSN:0028-3835    

DOI:10.1159/000122358

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Implants of cocoa butter (CB) or CB and actinomycin D (AD) were placed in the hypothalamus, amygdala, or anterior pituitary gland of testosterone-pretreated ovariectomized rats. The animals were then given an injection of 2.5 mg progesterone (P) at 11.00 h and sacrificed at approximately 16.30 h. Serum LH was determined by radio-immunoassay. Implants of AD placed in or near the arcuate nucleus and in other sites in the ventromedial hypothalamus blocked P-induced LH release, but those placed in the preoptic area or ventrolateral hypothalamus were only partially effective. Implants of AD in the amygdala or anterior pituitary gland had no detectable effect on LH release. Approximately 70% of the radioactivity in implants of 3H-AD diffused from the implant site within 8 h. Of that recovered, most was found within 1 mm of the implant site. These results suggest that the ventromedial hypothalamus is one site at which AD acts to block P-induced LH release.

ISSN:0028-3835    

DOI:10.1159/000122359

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The ability of 5-hydroxy-L-tryptophan (5-HTP) or pentobarbital anesthesia to elevate rat serum GH levels is completely blocked by the simultaneous administration of the serotonin antagonist cyproheptadine, as well as by the pineal gland principles melatonin and 5-methoxytryptamine (5-MT), and by the O-methylated dopamine derivative 3,4-dimethoxyphenylethylamine (DMPEA). Small doses of 5-MT cause paradoxical elevations in serum rat GH but at the same time inhibit the action of 5-HTP. Blockade of dopaminergic pathways by treatment with either DMPEA or chlorpromazine causes a slight, nonsignificant suppression of serum GH in normal rats while serum prolactin levels are increased greater than tenfold, showing that, unlike prolactin, rat GH is not subject to tonic inhibitory control by dopamine. The data presented support the recently advanced hypothesis that rat GH is under serotoninergic control and demonstrate that GH secretion can be significantly suppressed by serotoninergic blockade. It is suggested that the results presented here for monoamine control of rat GH release are not at variance with those reported for man.

ISSN:0028-3835    

DOI:10.1159/000122360

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Pentobarbital in a dose of 3.5 mg/100 g b.w. did not suppress the high basal a.m. levels of plasma ACTH in adrenalectomized male rats. In both intact and adrenalectomized rats prior administration of the drug slightly depressed the rise in plasma ACTH induced by 2.5 min of ether inhalation, but this depression is of questionable statistical significance.

ISSN:0028-3835    

DOI:10.1159/000122361

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Serotonin or melatonin was infused into the 3rd cerebral ventricle (3rd V) or into the medial basal hypothalamus (MBH) of both intact ewes and ewes with lesions of the anterior hypothalamic area (AHA). Prolongation of the estrous cycle and delay of ovulation were obtained after infusions of melatonin or serotonin in both the intact and lesioned ewes. Statistically, serotonin proved to be more effective in this respect than melatonin in the intact ewes. The infusions also blocked the preovulatory peak of LH. Furthermore, the infusion of serotonin blocked estrous behavior, while that of melatonin did not affect this function. The effect of indoleamie infusions in the lesioned ewes, in which the inhibitory action of the AHA over the transmission of gonadotrophic releasing hormones (G-RH) had been eliminated, seems to indicate that the inhibitory action of indoleamines on the release of these neurohormones is being displayed at the level of the MBH.

ISSN:0028-3835    

DOI:10.1159/000122362

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

A radioimmunoassay for luteinizing hormone-releasing hormone (LH-RH) is described which is capable of detecting LH-RH in plasma and brain tissues. Fluctuations in plasma and hypothalamic LH-RH as well as plasma LH were measured in immature female rats in which ovulation was induced by a single injection of pregnant mare serum (PMS). High plasma levels of LH-RH were found 47–49 h after the initial injection of PMS, coincident with high plasma LH concentrations. However plasma LH-RH levels were considerably lower at 55–57 h post-PMS, when plasma LH levels were elevated. Hypothalamic LH-RH content could not be correlated with either plasma LH-RH or LH lev

ISSN:0028-3835    

DOI:10.1159/000122363

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Prostaglandin E2 (PGE2) injected into the third ventricle (3rd V) of conscious ovariectomized rats bearing a permanent jugular cannula increased the percentage of plasma samples showing detectable immunoassayable LRF levels at 1, 3 and 5 min after injection. This percentage was small at 2 and 4 min. When plasma LRF and LH titers were measured in animals injected intraventricularly with PGE2 and decapitated 5 min later, both LRF and LH were significantly higher than control values of diluent-injected animals. These results indicate that PGE2 is acting on the hypothalamus to induce release of LRF sufficient in magnitude to be detected by measuring this neurohormone directly in peripheral plasma.

ISSN:0028-3835    

DOI:10.1159/000122364

出版商:S. Karger AG    

年代:1975

数据来源: Karger