摘要:

In unanesthetized water-loaded rats, intracerebroventricular (IVT) angiotensin II (All) injections produce centrally mediated pressor effects and antidiuresis. Experiments were performed to evaluate the role of antidiuretic hormone (ADH) release versus neurogenic mechanisms in the antidiuretic responses to central AIL Median eminence lesions used to block ADH release abolish antidiuretic effects but only attenuated pressor responses to IVT All infusions. Pretreatment with an intravenous infusion of ADH antibody had a similar effect. Central administration of All in water and saline-loaded rats produced no change in effective renal plasma flow or glomerular filtration rate. Natriuretic and kaliuretic responses to IVT All injections were similar to those observed to intravenous ADH infusions. These data are consistent with the suggestion that antidiuresis and osmotic excretion observed after IVT All injections in the rats are the result of ADH release, and that neurogenic mechanisms play a major role in the blood pressure but not in the antidiuretic responses.

ISSN:0028-3835    

DOI:10.1159/000122874

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The effects of K+-enhanced and Ca++-free media on α-MSH and adrenocorticotropic hormone (ACTH) release from superfused neurointermediate lobe (NIL) were studied in the same experiments. High K+ caused reversible and repeatable inhibition of α-MSH release and stimulation of ACTH release. Removal of Ca++ impaired the effect of K+, irreversibly for α-MSH and reversibly for ACTH. The existence of both melanotrophic and corticotrophic cells within the intermediate lobe (IL) of rat hypophysis could account for the different effects of ionic modifications on in vitro α-MSH and ACTH rele

ISSN:0028-3835    

DOI:10.1159/000122875

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

L-3,4-dihydroxyphenylalanine (L-dopa) was administered intraperitoneally (i.p.) to sexually experienced male rats, and blood was collected both by decapitation without anesthesia and by cardiac puncture with ether anesthesia. Samples were taken before and during mating with a receptive female. Both the prolactin (Prl) response to ether and the Prl response to mating were suppressed by L-dopa. Basal Prl levels were depressed, but not significantly. However, sexual behavior was not altered by L-dopa. It was concluded that the previously reported loss of the Prl response to an estrous female in male rats lesioned in the medial preoptic area (MPOA) could not account for their loss of sexual behavior. Further, elevation of Prl levels during mating is not necessary to normal sexual behavior in the intact male rat.

ISSN:0028-3835    

DOI:10.1159/000122876

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The effect of hypothalamic lesions on estradiol-induced changes in plasma luteinizing hormone (LH) concentration was studied in ovariectomized ewes. The ewes had stainless steel electrodes chronically implanted in the hypothalamus (HYP), and electrolytic lesions were made within 1 h after the injection of 50 μg estradiol benzoate (EB) i.m. Blood samples were collected at 2–6 h intervals for 30 h after EB, and the plasma was subsequently assayed for LH. None of the lesions produced had any effect on the normal immediate (within 12 h after injection) inhibitory effect of estrogen on LH release. However basal hypothalamic lesions, ranging from the suprachiasmatic region back over the optic chiasma down to include the anterior tuberal region, effectively inhibited the normal stimulatory effect of estrogen (12–30 h after injection) on LH release. The results are consistent with the interpretation that, in the normal biphasic LH response to injected estrogen in the ewe, the early inhibition of LH release results from direct inhibition of pituitary sensitivity to endogenous LH-releasing factor (LRF). On the other hand the estrogen-induced LH release which occurs subsequent to this inhibitory phase is principally the result of increased LRF secretion by the

ISSN:0028-3835    

DOI:10.1159/000122877

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The effect of 3 dopamine (DA) mimetic drugs, i.e. bromocriptine (Bro), apomorphine (Apo) and L-3,4-Dihydroxyphenylalanine (L-dopa), was evaluated on plasma growth hormone (GH) levels in 18 patients with Huntington’s chorea (HC). 27 nonobese hospitalized patients were used as controls. Mean baseline GH levels were not altered in patients with HC. Oral administration of Bro (2.5 mg po) or L-dopa (500 mg), or subcutaneous administration of Apo (1.0 mg) resulted in a significantly greater and more prompt (Bro, L-dopa) increase in plasma GH in patients than in controls. These results suggest the presence of an altered dopaminergic regulation of GH secretion inH

ISSN:0028-3835    

DOI:10.1159/000122878

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The olfactory bulbs were electrochemically stimulated in non-anesthetized, freely moving rats, and the ovulatory response and serum luteinizing hormone (LH) levels were studied. The stimulus was applied at 11:30 h through unilateral stainless steel electrodes chronically implanted, and serial blood samples were obtained by way of a plastic cannula located in the jugular vein. Electrochemical stimulation (100 μA/60 sec) of the main olfactory bulbs in the ventral aspect of the superficial layers as well as in its central core, performed on the day of proestrus, prevented the preovulatory discharge of LH and ovulation. Blockade of ovulation also occurred when the stimulus was applied in the lateral or medial parts of the superficial layers. On the other hand, stimulation in the dorsal part blocked the preovulatory surge of LH and ovulation in only 50% of the cases. Stimulation applied in the accessory olfactory bulbs failed to interfere with ovulation and LH discharge. Stimulation of ovariectomized estrogen-primed rats applied in the superficial layers of the main olfactory bulbs had no significant effect on the release of LH, but when the stimulus was applied in the accessory olfactory bulb a release of LH took place 3–6 h following stimulation. These results indicate that stimulation of the olfactory bulbs produce a dual effect on LH release: while the response of the accessory olfactory bulb is facilitatory in nature, that of the main olfactory bulbs is inhibito

ISSN:0028-3835    

DOI:10.1159/000122879

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Rats that were maintained on a 23-h food and water deprivation schedule (food and water available between 09:00 and 10:00 h) for 21 days, and whose blood was sampled at various times following initiation of ingestion showed a decrease in plasma adrenocorticotrophin (ACTH) concurrent with dropping plasma levels of corticosterone (COR). This drop occurred from elevated levels of these hormones, most likely due to altered circadian patterns of pituitary-adrenal activity as a result of the rhythm-entraining properties of the feeding schedule. This inhibition of secretion of ACTH is interpreted as reflecting the inhibitory effect of a central nervous system mechanism that can affect ACTH secretion independently of corticosteroid negative feedback.

ISSN:0028-3835    

DOI:10.1159/000122880

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The enzyme kinetic parameters of the degradation of luteinizing hormone-releasing hormone (LH-RH) and L-cystine-bis-(4-nitroanilide) (Cys-NA) by rat hypothalamic (HYP) and pituitary (PIT) extracts and the effect of various oligopeptides on the rate of LH-RH inactivation were investigated in vitro. The 105,000 × g supernatant of 1 rat HYP inactivated 57 μg LH-RH during a 30 min incubation (Km = 12.4 μM,Vmax = 2.33 μg LH-RH/mg protein/min), and of one rat anterior PIT, 48 μg LH-RH during 30 min of incubation (Km = 12.2 μM, Vmax = 8.0 μg LH-RH/mg protein/min). The synthetic substrate Cys-NA competitively inhibited LH-RH degradation with a Ki of 8.5 μM in the HYP and 6 μM in the PIT enzyme preparation. Vice versa, LH-RH also competitively inhibited the cleavage of Cys-NA with inhibition constants of 14 μM (HYP) and 15 μM (PIT) indicating that the 2 substrates are probably cleaved by the same enzyme. The most effective inhibitors of LH-RH degradation were found to be angiotensin-related peptides, neurotensin, bradykinin, and bacitracin. A relatively weak effect was obtained with oxytocin, enkephalin and puromycin. It is concluded that endogenous oligopeptides such as angiotensins, neurotensin, bradykinin, etc., may possibly influence LH-RH degradation in the PIT and the HYP. The synthetic substrate Cys-NA may be an appropriate substrate for measuring the activity of an LH-RH-degrading peptidase, which therefore could be classified as a

ISSN:0028-3835    

DOI:10.1159/000122881

出版商:S. Karger AG    

年代:1979

数据来源: Karger