摘要:

The present study was undertaken to investigate the effect of osmotic constituents of the incubation media on angiotensin II stimulation of arginine vasopressin (AVP) release from the organ-cultured guinea pig hypothalamo-neurohypophyseal complex (HNC). As reported previously, the addition of angiotensin II caused a significant increase in AVP release from the explants of HNC incubating in the normal culture medium. The media made hyperosmolar with sodium chloride also significantly increased AVP release from the explants. The addition of angiotensin II to the hyperosmolar sodium chloride caused a further increase in AVP release from the explants of HNC. However, the response to angiotensin II was not significantly different among the explants incubating in the hyposmolar, the isosmolar and the hyperosmolar sodium chloride solutions, indicating separate pathways of angiotensin II and osmotic stimuli in AVP release. In contrast, the response of the explants to angiotensin II was markedly suppressed when they were incubated in the media made hyperosmolar with excess glucose. Furthermore, the hyperosmolar media of excess urea failed to influence the angiotensin II-stimulated AVP release from the explants. These results are compatible with the hypothesis that excess glucose has a specific suppressive effect on AVP release from the neurohypophysis.

ISSN:0028-3835    

DOI:10.1159/000123104

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Plasma corticosterone levels during lactation were examined in inbred A/J (A) and C57BL/6J (C)mice. Following shock, lactating A females showed a diminished corticosterone response relative to nonlactating controls on day 5 of lactation, but not on day 12. In contrast, plasma corticosterone levels of lactating C females 5 and 15 min following shock were lower than those of controls on day 12, but not on day 5. Consistent with these findings, lactating A females had significantly lower plasma levels of corticosterone 15 min following nonnociceptive treatments (involving distrubance, exposure to novelty, and pup manipulation) when tested on day 5 than they did when tested on day 12, whereas lactating C females had lower levels on day 12 than on day 5. Lactating females of each strain showed the same response to shock on day 12 if they reared A pups as they did if they reared C pups. This indicates that the difference found between the strains on day 12 was due to a difference in some property of A and C mothers, rather than to a difference in a characteristic, such as suckling patterns, of the pups of the two strains. It was also found that at long intervals following shock (45 and 90 min) 5-day lactating C females had higher levels of plasma corticosterone than did controls. There was no effect of lactation on resting adrenocorticoid levels in A or C females at either 5 or 12 days. The results indicate that laboratory mice show changes in hypothalamo-pituitary-adrenal activity during lactation which both vary with strain of the mother, and differ in several respects from those previously reported for rats.

ISSN:0028-3835    

DOI:10.1159/000123105

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Experiments were undertaken to demonstrate the existence of a physiological role of prolactin releasing factor (PRF). Hypothalamic control of prolactin secretion is achieved by secretion of prolactin inhibiting factor (PIF) and/or PRF. Since the putative PIF is dopamine, complete blockage of the dopaminergic PIF receptors should permit demonstration of PRF activity. The changes in prolactin concentration were monitored by taking a blood sample every 2 min through an indwelling atrial cannula. An excessive amount of pimozide (3 mg/kg) was used to block dopaminergic receptors and prolactin concentration was elevated as a result. This higher concentration of circulating prolactin was maintained for more than 30 h after a bolus injection of pimozide. In this situation, lacking functional dopaminergic PIF receptors, there were fluctuations in the circulating prolactin concentration throughout the experiment. If, after pimozide administration, rats were exposed to an acute (ether) stress, the stress consistently elevated the circulating prolactin concentration. Since there are no functional dopaminergic PIF receptors available under these conditions, a dopaminergic PIF cannot be involved in producing the prolactin surge induced by the acute stress. Therefore, these results suggest that a physiological PRF is involved in the generation of this prolactin surge, though the evidence is not direct.

ISSN:0028-3835    

DOI:10.1159/000123106

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The pressor effect of intravenous angiotensin II (AII) was compared in the unrestrained rat before and after electrolytic lesions of the subfornical organ (SFO), the circumventricular organ of the dorsal third cerebral ventricle. Abdominal aortic and venal caval catheters were used to measure arterial pressure and to infuse solutions, respectively. The pressor effect of AII was significantly reduced following complete SFO lesions but was unaffected by partial SFO lesions or by control lesions in adjacent tissue. The pressor effect of intravenous infusion of the alpha-adrenergic agonist, phenylephrine, was unaffected by any of these lesions. In agreement with experiments demonstrating that SFO injection of AII increases arterial pressure, the present results suggest that a significant portion of the pressor action of circulating AII is centrally mediated, and that the SFO participates in this mediation.

ISSN:0028-3835    

DOI:10.1159/000123107

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Pituitary intermediate lobe melanocyte-stimulating hormone (MSH) is responsible for normal skin darkening in amphibians. Light-background adapted frogs (Rana pipiens) injected with naloxone and placed on black backgrounds maintain melanophore indices and pituitary cytology characteristic of light-background adaptation. In vitro and in vivo experiments showed that naloxone hydrochloride did not have a direct effect on skin melanophores or on the neurointer-mediate lobe. These data suggest that naloxone acts at the level of the central nervous system to inhibit the mechanism(s) responsible for release of MSH when light-background adapted frogs are placed on a dark background. Release of MSH, known to be tonically inhibited by the hypothalamus, may be modulated by opiate receptor-dependent mechanisms.

ISSN:0028-3835    

DOI:10.1159/000123108

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Studies on the mechanisms which govern the release of prolactin were undertaken using two in vitro techniques. A dispersed preparation of rat anterior pituitary cells was made by mechanical means in the presence of trypsin. These washed cells were drawn up into a small column together with a Bio-Gel matrix and perifused with Earle’s basic salt solution. The eluates containing prolactin were then collected at short intervals. Test substances were added to the perifusion medium and their effect on prolactin release was measured. The results of these studies were compared with those obtained by incubating hemipituitary glands in Medium 199 to measure the effect of test substances on the release of radioimmunoassayable prolactin. Perifusion of dispersed pituitary cells with dopamine produced a marked inhibition of prolactin release within 3 min, and maximal suppression was noted 11 min after initiating the perifusion. Upon withdrawal of dopamine, prolactin release began to recover within 1 min and continued to rise to 80% of baseline at 6.5 min. Perifusion of pituitary cells in medium free of calcium also produced a marked reduction in prolactin release which was restored after reexposure of the cells to calcium. The addition of manganese and D-600, agents which block calcium channels, also caused reversible inhibition of prolactin release. The effects of the ionophores A23187 and X537A on prolactin release were studied. The presence of calcium ionophore A23187 did not effect prolactin release but it reversed the dopamine-mediated inhibition of prolactin release. In the absence of calcium, both ionophores stimulated release of prolactin. Tetrodotoxin, a blocker of sodium channels had no effect on prolactin release. Agents such as prostaglandin E1, and cholera toxin increased cyclic AMP levels, but no positive correlation was obtained on prolactin release patterns. Gpp(NH)p-stimulated adenylate cyclase activity in homogenates of anterior pituitary tissue was unaffected by dopamine. In contrast, addition of dibutyryl cyclic AMP to perifused pituitary glands stimulated prolactin release and theophylline added to hemipituitary gland completely reversed the inhibitory effect of dopamine on prolactin release and caused a concomitant increase in cyclic AMP levels. It is suggested that the tonic high level of prolactin release is maintained by influx of extracellular calcium and that dopamine inhibits this process. The role of intracellular cyclic AMP is undefined; however, the effects of dibutyryl cyclic AMP and theophylline may be due to mobilization of intracellular calcium and thereby stimulate prolactin release by this mechanism rather than through cyclic AMP. In summary, we present evidence that regulation of prolactin secretion by normal lactotropes is a calcium-mediated proces

ISSN:0028-3835    

DOI:10.1159/000123109

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Female guinea pigs are more sensitive than males to the lordosis-promoting effects of sequential estradiol-progesterone treatment. This study explored a possible cellular basis for this reduced sensitivity. Cytoplasmic progestin receptor concentrations were determined using a [3H]R5020 binding assay for a dissection of brain tissue which included the hypothalamus, preoptic area and septum (HPS) from male and female guinea pigs 40 h after administration of estradiol ben-zoate (EB). Male guinea pigs injected with 10 μg EB have a progestin binder in cytosol from HPS and cerebral cortex that is similar to that in females on the basis of apparent dissociation constant and steroid specificity. Injection of either 1.6 or 10 μg EB caused a larger increase in the concentration of cytoplasmic progestin binding in female HPS compared to the same dose in males. A 10 μg EB injection induced a concentration of progestin binding in male hypothalamus not significantly different from that induced in female hypothalamus by a 1.6 μg EB injection (a dose that consistently facilitates sexual recepivity in females when followed 40 h later by 0.5 mg progesterone). Despite the induction by EB of a behaviorally-sufficient concentration of cytoplasmic progestin receptors, fewer males (3/10) than females (8/10) responded to EB (10 μg)-progesterone treatment with the expression of lordosis. Finally, using a nuclear progestin receptor [3H]R5020 exchange assay, we found that male guinea pigs injected with 10 μg EB accumulated a slightly lower concentration of progestin receptors in HPS cell nuclei 4 h after a 0.5 mg progesterone injection than similarly-treated females. Therefore, male guinea pigs show decreased induction of cytoplasmic progestin receptors in HPS after estradiol injection, and a decreased cell nuclear accumulation of these receptors after progesterone injection compared to females. We conclude that this sex difference in the progestin receptor system is insufficient to account, in itself, for the sex difference in behavioral sensitivity to estradiol and progest

ISSN:0028-3835    

DOI:10.1159/000123110

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

We have summarized here recent evidence that clarifies the cellular organization and connections of the paraventricular nucleus of the hypothalamus (PVH) in the rat. The nucleus consists of a magnocellular division, with three distinct parts, and a parvocellular division with five distinct parts. Most neurons in the magnocellular division contain either oxytocin or vasopressin, and project to the posterior lobe of the pituitary gland. Separate cell populations centered in the parvocellular division give rise to projections to the median eminence, or to the brain stem and spinal cord including the intermediolateral column; some cells project both to the dorsal vagal complex and to the spinal cord. Cells with long descending projections may contain either oxytocin, vasopressin, somatostatin, or dopamine, although the biochemical specificity of most such neurons has not been determined. Noradrenergic fibers are found preferentially within those parts of the magnocellular division that are predominantly vasopressinergic. The parvocellular division is innervated by adrenergic as well as noradrenergic fibers from the brain stem, and by fibers from the dorsal vagal complex and the parabrachial nucleus. The bed nucleus of the stria terminalis and adjacent parts of the hypothalamus also innervate the PVH. The evidence indicates that subpopulations of neurons in the PVH are directly related to autonomic and neuroendocrine effector mechanisms, and suggests that the nucleus plays an important role in the regulation of visceral responses in the periphery and in the CNS itself.

ISSN:0028-3835    

DOI:10.1159/000123111

出版商:S. Karger AG    

年代:1980

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000123112

出版商:S. Karger AG    

年代:1980

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000123113

出版商:S. Karger AG    

年代:1980

数据来源: Karger