摘要:

Intravenous injections of chlorpromazine(200 µg/100 g b.w.) or pentobarbital (2 mg/100 g b.w.) caused significant increases in both plasma growth hormone (GH) and prolactin levels in urethane-anesthetized rats. The concurrent administration of nicotine (0.02 mg/ 100 g b.w. i.p.) significantly blunted plasma GH responses to chlorpromazine and to pentobarbital, whereas plasma prolactin responses to these drugs were not affected. The inhibiting effect of nicotine on chlorpromazine-induced GH release was also observed in rats with hypothalamic deafferentation. These results suggest that nicotine suppresses GH secretion via the hypothalamus in rats

ISSN:0028-3835    

DOI:10.1159/000122570

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Female albino rats exposed to constant light are anovulatory and show an extensive loss of retinal photoreceptors but resume regular ovarian cycles when returned to light-dark conditions. If returned to constant light such animals develop persistent vaginal cornification at the same rate as animals with intact retinas exposed to constant light for the first time. Pigmented rats exposed to constant light may become anovulatory without any retinal changes at the light microscopic level. Possible mechanisms involved in the light-induced blockade of ovulation in the female rat are discussed.

ISSN:0028-3835    

DOI:10.1159/000122571

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The injection into the 3rd ventricle of betha-nechol, carbachol and noradrenaline provoked the release of antidiuretic hormone (ADH) in the hydrated male rat, as indicated by a decrease in urine flow and free-water clearance, with an increased urinary electrolyte concentration, osmolality and conductivity. Atropine completely blocked the bethanechol- and carbachol-induced anti-diuresis, whereas phentolamine and pentolinium did not. On the other hand, the noradrenaline-induced antidiuresis was blocked by phentolamine, but not by atropine or pentolinium. Intraventricular injections of different doses of nicotine did not elicit any release of vasopressin. It is therefore concluded that separate synapses with the neurosecretory cell of both cholinergic muscarinic and α-adrenergic origin exist

ISSN:0028-3835    

DOI:10.1159/000122572

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The effects of testosterone, dihydrotestosterone, and otherandrogens upon gonadotropin secretion were studied using isolated female rat pituitaries maintained for 5 days. FSH and luteinizing hormone (LH) were measured by radioimmunoassay. When mean FSH release and mean final tissue content of FSH were compared in preparations containing testosterone or dihydrotestosterone (5 ng/ml) in the presence of 4 × 10–4 M dibutyryl cyclic AMP (vs dbcAMP alone), both release and tissue content were significantly increased. Dihydrotestosterone, but not testosterone, significantly reduced LH release. Similiarly, in experiments utilizing LH-releasing hormone (LRH, 1.5 ng/ml), a significant increase in FSH release (128% of control values during the final 3 days of culture) and a significant increase in tissue content (152% of control values) were obtained in the presence of testosterone. Thus, testosterone in the presence of LRH did not inhibit gonadotropin release; rather, the secretion of FSH seemed to be stimulat

ISSN:0028-3835    

DOI:10.1159/000122573

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The effect of an intraperitoneal injection of estradiol benzoate (EB) upon cyclic AMP accumulation in the hypothalamus of 21-day-old rats was studied. Clomiphene citrate administration prior to EB neutralized the estrogen-induced accumulation of hypothalamic cyclic AMP. The increase in cyclic AMP caused by EB was abolished by prior treatment with adrenergic receptor blockers. These results suggest the involvement of adrenergic receptor mechanism(s) in the transmission of the estrogen stimulus in the hypothalamus.

ISSN:0028-3835    

DOI:10.1159/000122574

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The present study was made to investigate the possible effects of dexamethasone and secobarbital on the pituitary responses of prolactin (PRL) and TSH to TRH. Dexamethasone (1 mg) and secobarbital (100 mg) were administered separately or together at 11 p.m. An intravenous injection of 200 µg TRH was given at 9 a.m. the following morning. PRL control levels and release were not modified by prior administration of the drugs. TSH control levels remained unchanged but TSH release was significantly inhibited by the combined pre-treatment; dexamethasone and secobarbital given alone had no effect. The present study supports the view of a direct synergistic effect of both drugs on the pituitary thyrotropes, diminishing their responsiveness to TRH

ISSN:0028-3835    

DOI:10.1159/000122575

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Normal male rats were subjected to a variety of stress stimuliincluding simple handling, transfer from room to room, ether anesthesia alone or combined with bleeding, the injection of saline or epinephrine, and restraint. The ensuing secretory responses of prolactin, LH, GH and FSH were then determined. Although the secretion of all 4 hormones is affected by stress and their secretory responses have a nonspecific character, they differ both in susceptibility and reactivity to stress stimulation. The secretions of prolactin and GH are the most susceptible, and whereas the secretion of prolactin is enhanced, the secretion of GH is inhibited. The secretion of LH is less susceptible and the secretory responses are more complex: an initial stimulatory phase is often followed by an inhibitory phase. The secretion of FSH is the least susceptible, but when a secretory response is elicited, it is paralleled by the secretory change in LH.

ISSN:0028-3835    

DOI:10.1159/000122576

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Intense, long-lasting darkening of theskin color of the frog, Rana nigromaculata, was demonstrated by autotransplantation of the pars neurointermedia into the anterior chamber of the left eye. At 4 months post-operative, catecholamines were injected into the eye. It was found that: (1) catecholamines produce a marked bleaching effect when injected into the left eye containing the transplant; (2) catecholamines show a very weak and short bleaching effect when injected into the intact, right eye; (3) no bleaching effect is observed when a solvent of catecholamines is injected into the right and left eyes; and (4) in the transplanted pars intermedia, the droplets of acidophilic colloid increase in number and accumulate in the vicinity of the blood capillaries within the gland and of those adjacent to the pars nervosa. These droplets decrease remarkably after the injection of catecholamines into the left eye with the transplant. These findings led to the conclusion that catecholamines have a direct effect on the pars intermedia, blocking the release of MSH from the gland cells, thus resulting in a pallor of the skin color.

ISSN:0028-3835    

DOI:10.1159/000122577

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The long-term effect of hypothalamic lesions onplasma and pituitary levels of melanocyte-stimulating hormone (MSH) was examined in male rats. Lesions of the paraventricular nuclei (PVN) produced a large increase in both plasma and pituitary MSH levels, whereas lesions of the supra-optic nuclei had little effect. These results support the idea that MSH secretion is under an inhibitory control by the hypothalamus and suggest that the PVN are involved. The PVN may be involved in the release or production of an MSH release inhibiting factor (MIF), although the present results do not exclude the possibility that the PVN control MSH secretion through a direct innervation of the pars intermedia.

ISSN:0028-3835    

DOI:10.1159/000122578

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Fetal and adult rat pituitaries were incubated intissue culture medium to which, during periodic intervals, varying concentrations of synthetic LH-FSH-RH were added. Several methods of incubation were tested and the medium was assayed by radioimmunoassay to determine changes in the release of FSH and LH. Superfusion and long- and short-term incubations resulted in increased gonadotropic hormonerelease during exposure to releasing factor (RF). The most reliable method of incubation was the latter method involving a 3-h incubation period. It is concluded that fetal pituitaries during late gestation are capable of responding to the presence of RF by increased hormone release.

ISSN:0028-3835    

DOI:10.1159/000122579

出版商:S. Karger AG    

年代:1974

数据来源: Karger