摘要:

The prolactin (PRL)-releasing effect of domperidone (DOM), a blocker of dopamine receptors which does not cross the blood-brain barrier, was studied in unanesthetized male rats and compared to that of the classic neuroleptic agent haloperidol (HAL). DOM proved to be a potent PRL releaser since striking and long-lasting (120 min) rises in plasma PRL were elicited by 50 and 100 μg/kg of the compound. Comparison with HAL showed that DOM was 5 times as potent as HAL as a PRL releaser (ED250 = 0.084 vs. 0.42 mg/kg, respectively). Apomorphine (APO) fully counteracted the PRL-releasing effect of DOM (0.1 mg/kg i.p.) only at the dose of 3 mg/kg s.c, while the PRL-releasing effect of HAL (0.1 mg/kg i.p.) was blocked by APO at the dose of 1 mg/kg s.c. The effect of DOM (0.1 mg/ kg i.p.) on PRL release was also suppressed by another DA-agonist drug, bromocriptine (5 mg/kg s.c). Evaluation of the affinity of DOM and HAL on [3H]-spiperone binding to striatal and pituitary homogenates showed a slightly higher affinity for DOM than HAL on both tissue. Systemic administration of DOM (50 and 100 μg/kg i.p.) left homo-vanillic acid (HVA) concentrations unchanged in the caudate nucleus while, as expected, HAL (0.5 and 1.0 mg/kg i.p.) induced a striking rise in striatal HVA content. These results indicate that DOM, by acting at the level of ‘peripheral’ DA receptors, is a strong PRL-releasing

ISSN:0028-3835    

DOI:10.1159/000122977

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The effects of pituitary stalk section on anterior pituitary secretion were studied in 20 female rhesus monkeys. Vascular connections between the hypothalamus and the pituitary gland were permanently interrupted in all but 4 animals. Prolactin levels rose rapidly and remained significantly elevated in all effectively stalk-sectioned animals for as long as the observation period (up to 3 years). Only smaller and transient elevations of prolactin were seen in the animals in which revascularization of the anterior pituitary gland had occurred. Growth hormone and cortisol were significantly decreased after stalk section, and were not released by insulin. Radioimmunoassayable luteinizing hormone (LH) levels decreased following surgery and, by bioassay, LH became undetectable within 5 weeks after stalk section, indicating that gonadotropin-releasing hormone is essential for the viability of the gonadotrope. The results indicate that plasma prolactin concentrations can be used to monitor completeness of pituitary gland isolation from direct hypothalamic influence. Stalk-sectioned monkeys provide good models to study direct pituitary effects of various hormones or drugs.

ISSN:0028-3835    

DOI:10.1159/000122978

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The effects of pituitary stalk section on anterior pituitary morphology were studied in 18 female rhesus monkeys. 4 animals were studied within 1–14 days after the operation, while the others were examined later (average 17.2 months). In 3 monkeys there was no necrosis of the anterior lobe, whereas in the remaining animals, an area of infarction averaging 20% was found. Using immunocytochemical techniques, we found that corticotropes and somato-tropes were still present following the procedure, and that the number of lactotropes increased markedly. In contrast, gonadotropes, although present in the pars tuberalis, were no longer demonstrable in the pars distalis 3 weeks after stalk section. These results show remarkable agreement between endocrine studies and morphological observations, and indicate a variable degree of dependency of the various pituitary cells on central nervous system influence

ISSN:0028-3835    

DOI:10.1159/000122979

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The effects of 6-chloromelatonin and 6-fluoromelatonin on ovulation and LH and prolactin release in rats were determined. Both halogenated melatonin analogs were more potent ovulation blockers than melatonin. The halogenated melatonin analogs inhibited the ovulatory surge of luteinizing hormone (LH) but did not alter the proestrous prolactin surge, nor did they alter basal serum levels of LH or prolactin. The plasma half-life of 6-chloromelatonin in rats and rhesus monkeys was 27 min compared to 11 min for melatonin. The results indicate that 6-chloromelatonin is a melatonin agonist with greater metabolic stability than melatonin.

ISSN:0028-3835    

DOI:10.1159/000122980

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The mitotic index of Yoshida ascites tumor cells was significantly higher in rats that underwent tuberoinfundibular destruction than those lesioned in other regions of the hypothalamus or in the cerebral hemispheres or in sham-operated animals. Survival was shorter in the rats lesioned in the tuberoinfundibular and posterior hypothalamic regions. The rise in the mitotic index of Yoshida ascites tumor cells is consistent with the results of previous work showing significantly increased cell proliferation in the normal tissues of animals lesioned in the tuberoinfundibular region.

ISSN:0028-3835    

DOI:10.1159/000122981

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The effects of subcutaneous and medial basal hypothalamic (MBH) implantation of testosterone (T) on LHRH contents and norepinephrine (NE) and dopamine (DA) concentrations and turnover in the MBH and the preoptic area (POA) were studied in castrate rats; serum levels of LH, FSH and T were also monitored. Subcutaneous T implants elevated serum T levels to those normally observed in intact rats and this resulted (i) in marked increments in the MBH LHRH content and reduced serum LH and FSH levels, (ii) in reduced turnover of NE without altering that of DA in the MBH, and (iii) in a concomitant decrease in the POA DA turnover rate. Following implantation of T in the MBH there was no significant rise in serum T concentration. As in the case of s.c. T implants, these MBH implants suppressed serum gonadotropin levels and reduced the turnover of the MBH NE without affecting that of DA. The effects of the MBH T implants were apparently local since the turnover of neither catecholamine in the POA was altered. From these observations it is reasonable to conclude that (i) hypothalamic NE innervations possess the ability to respond to changes in T titers, (ii) the effects of T on NE activity are exerted within the MBH and accordingly, (iii) these changes in the MBH NE turnover following T administration may play a role in regulation of the MBH LHRH activity.

ISSN:0028-3835    

DOI:10.1159/000122982

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

To determine if serotonin plays a role in the regulation of renin secretion, pentobarbital-anesthetized dogs were injected intravenously with drugs which modify serotonin metabolism. Renal perfusion pressure was kept constant by a clamp on the aorta proximal to the renal arteries. 5-Hydroxytryptophan (5-HTP) caused a significant increase (p < 0.05) in arterial plasma renin activity (PRA) that was abolished when peripheral and central aromatic amino acid decarboxylase activities were inhibited by administration of benserazide, but not reduced when only the peripheral decarboxylase activities were inhibited by administration of carbidopa. The serotonin receptor blocking drug metergoline also abolished the renin response to 5-HTP. L-Tryptophan in two different doses increased PRA. This increase was not reduced by carbidopa but was reduced or abolished by benserazide, metergoline, and renal denervation. The increase in PRA produced by 5-HTP and L-Tryptophan occurred without any change in blood pressure. 5-HTP had no effect on heart rate but L-Tryptophan reduced heart rate. These data indicate that 5-HTP and L-Tryptophan act on the central nervous system to produce an increase in renin secretion that is mediated via the renal nerves and occurs without a concomitant increase in sympathetic output to the heart or blood vessels. The increase appears to be due to the release of serotonin within the central nervous system.

ISSN:0028-3835    

DOI:10.1159/000122983

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Electrical stimulation of rat posterior lobes in vitro inhibited bioactive corticotropin (ACTH) release from the intermediate lobe and promoted the release of corticotropin-releasing factor(s) (CRF). Both effects were calcium dependent. Released posterior lobe CRF was inactivated by thioglycolate, and the CRF activity could be accounted for by vasopressin. Results suggest strongly that vasopressin is the predominant CRF released from neurohypophysial axons, and that intermediate lobe ACTH release is submitted to an inhibitory control.

ISSN:0028-3835    

DOI:10.1159/000122984

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The concentration of human β-endorphin (βh-EP) was measured in various hypothalamic nuclei, in extra-hypothalamic brain regions and in the anterior and posterior lobes of the pituitary using a specific radioimmunoassay (RIA). The βh-EP concentrations in the arcuate nucleus (169 ± 35 pg/100 μg protein, n = 7) and median eminence (163 ± 32 pg/100 μg protein, n = 6) were among the highest in the 17 brain areas examined. The immunoreactive βh-EP in the hypothalamus corresponded to authentic βh-EP, as determined by gel exclusion chromatography. By chromatography and RIA the βh-EP concentrations in anterior (1.53 × 105 ±0.51 × 105 pg/100 μg protein, n = 3) and posterior (1.41 × 105 ± 0.38 × 105 pg/100 μg protein, n = 5) pituitary were found to be approximately 1,000-fold higher than in hypothalamus. Within the pituitary βh-EP was localized throughout the anterior lobe, in the pars intermedia and in that part of the posterior lobe nearest the pars intermedia, as judged by immunocytochemistry. Dense immunocytochemical staining was found along the perimeter of many blood vessels. βh-EP and adrenocorticotropin (ACTH) were co-localized in the same pituitary cells. The present data represent the first unequivocal localization and quantitation of βh-EP in human brain and in the separate lobes of

ISSN:0028-3835    

DOI:10.1159/000122985

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

This review considers some of the neuroendocrine factors influencing pulsatile LH secretion. Such release is apparently due to the pulsatile discharge of LHRH from brain peptidergic neurons. This is a physiologically important event since a periodic rather than continuous input signal to the pituitary gland prevents it from becoming refractory to LHRH stimulation. Pulsatile secretion of LH, in the rat at least, does not appear to be regulated solely by the medial basal hypothalamus. Central noradrenergic, cholinergic, dopaminergic, and serotoninergic systems are involved in influencing episodic LH release, presumably by affecting pulsatile LHRH secretion. Moreover, several hypothalamic as well as extrahypothalamic areas appear to play integral parts in controlling the rhythmic alterations in blood LH levels. These regions include the arcuate and suprachiasmatic nuclei, perisuprachiasmatic area, medial preoptic area, and midbrain dorsal raphe nucleus. Ovarian steroids also exert important influences on pulsatile LH release, and greatly modify the response of this secretory system to neurotransmitters and stimuli from certain brain regions.

ISSN:0028-3835    

DOI:10.1159/000122986

出版商:S. Karger AG    

年代:1980

数据来源: Karger