摘要:

The purpose of this study was to determine the effect of rendering newborn male Sprague-Dawley rats hypothyroid with 131I on development of the hypothalamic-pituitary axis. Hormonal responses to thyrotropin-releasing hormone (TRH). haloperidol (H), and luteinizing hormone-releasing hormone (LHRH) were determined at 9, 15, 30 and 75 days of age in hypothyroids and controls. Basal and TRH-stimulated thyroid-stimulating hormone (TSH) levels were higher in the hypothyroids, but the developmental patterns of basal TSH secretion and TSH reserve were parallel in the two groups, with maximal TSH secretion occurring at 30 days. Basal prolactin (PRL) and PRL responses to TRH and H were less in the hypothyroids at all ages. Basal LH and LH responses to LHRH were greater in the controls at days 9 and 15, but the hypothyroid rats displayed greater basal and stimulated LH secretion at 30 days and values similar to controls at 75 days of age. These results suggest that development of the hypothalamic-pituitary axis is altered in rats rendered hypothyroid shortly after birth.

ISSN:0028-3835    

DOI:10.1159/000123011

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Alterations in the ionic composition of the medium and different secretagogues have been used in order to study the mechanism of release of ACTH from superfused neurointermediate lobes (NIL) of rat hypophysis. We showed that: (a) a tenfold increase of K in the medium caused a reversible and repeatable stimulation of the ACTH release; (b) removal of Ca ‘ : reversibly abolished the stimulating effect of high K +: (c) removal of Ca’ had no effect on the stimulating effect of a hypothalaniic extract (HE); (d) in the latter case, a reversible significant weakening was obtained by the addition of EDTA in the Ca++-free medium; (e) dbc-AMP caused a reversible and repeatable stimulation of the ACTH release; (f) comparable results were obtained for anterior lobes (AL) superfused in the same conditions. From these data we can conclude that Ca++ is necessary for the stimulation of the hormonal release and that factors such as K or dbc-AMP can mimic the in vitro stimulating effect of a HE. Similarities, which appear in this study, between the modulation of the ACTH release from NIL and AL. led us to support the idea that, in vivo, a release of ACTH from the NIL, may occur in physiological conditi

ISSN:0028-3835    

DOI:10.1159/000123012

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The multiple unit activity of the rat neural lobe was investigated to determine how accurately it represents the neural events accompanying the actual release of hormones by the neurohypophysial system. Microelectrode recordings were done in normal and midbrain-transected rats to identify the unit activity belonging to the neural lobe and to characterize its activity. Following the intracarotid bolus injection of hypertonic saline, the neural lobe responded with several complex patterns. Each one of them was made up of one or more of five different possible events: initial burst, short inhibition, delayed bursting activity, prolonged increase and prolonged inhibition. The neural lobe response usually lasted long after the brief osmotic stimulation was over. Some of the patterns of unit activity found in the neural lobe reflected the reported pulsatile patterns of hormone release following hypertonic stimulation revealed by sequential measurement of plasma vasopressin levels. The rats with midbrain transection did not show the short inhibition event, probably as a result of the removal of information impinging on the system from peripheral sources coming from or through the mesencephalon.

ISSN:0028-3835    

DOI:10.1159/000123013

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Injection of 10 μg of carbachol into a lateral cerebral ventricle caused a large reduction in urine flow and free water clearance and an increase in urine osmolality in water-loaded sheep. This antidiuretic effect persisted for at least 1 h. and was prevented by a prior intracerebroventricular (ICV) injection of atropine (100 μg). ICV injections of atropine (100 μg) given 10 min before and again midway through an intracarotid infusion of 2 M NaCI at 0.8 ml/min for 10 min did not alter the antidiuretic response which normally follows this hypertonic stimuli. It was concluded that in sheep, while periventricular cholinergic synapses capable of influencing antidiuretic hormone may exist, it is unlikely that ADH secretion in response to hypertonicity is mediated through such synapses. Cholinergic synapses located further from the cerebroventricular surface are not excluded from mediating the antidiuretic response to hypertonici

ISSN:0028-3835    

DOI:10.1159/000123014

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Neonatal administration of monosodium glutamate (MSG) produces neurotoxic degeneration of the retina and medial-basal hypothalamus, including the arcuate nucleus. Since this hypothalamic area contains the only neuronal cell bodies in brain which contain adrenocorticotrophic hormone (ACTH) and β-lipotropin (β-LPH) and β-endorphin, destruction of these cells by MSG may interfere with pain responses mediated by nerve fibers arising from these perikarya. The present study examined whether MSG-treated rats, as compared to Iittermate controls, exhibited concomitant changes in the immunocytochemical distribution of ACTH and β-LPH, and their reactivity to several analgesia-inducing manipulations. Although MSG-treated rats did not differ from control rats in their baseline reactivity to electric shock, they displayed an inability to exhibit analgesia following acute exposure to cold-water swim stress. In addition, MSG-treated rats showed an attenuated analgesic response following morphine administration. However, the analgesia elicited by either abrupt food deprivation, or the glucoprivic stress of 2-deoxy-Z)-glucose, was unaffected by neonatal MSG treatment. Concomitant with these selective analgesic deficits, MSG-treated rats displayed a marked immunocytochemical reduction in ACTH/β-LPH perikarya and terminals in brain, but not pituitary. These data indicate that multiple pain-inhibitory systems exist, and that some rely upon an intact medial-basal hypothalamus to produce analg

ISSN:0028-3835    

DOI:10.1159/000123015

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Using radioautography and immunocytochemistry, we investigated differences in 3H-cytidine incorporation into RNA in vasopressin or neurophysin-positive neurons in the rat hypothalamus following adrenalectomy. Control animals and those that had been bilaterally adrenalectomized for 2 weeks received 0.3 mCi 3H-cytidine subcutaneously and were decapitated 1 h following injection. Brains were prepared for combined radioautography and immunocytochemistry. Incorporation was estimated by counting silver grains over immunoreactive neurons. The neurons of the paraventricular nucleus (PVN) showed a consistent and significant increase in the amount of incorporation of label 2 weeks after bilateral adrenalectomy. There was no change in incorporation in neurons of either the supraoptic or suprachiasmatic nuclei. These findings suggest that the vasopressin PVN neurons, some of which project to the zona externa of the median eminence, are activated under conditions of adrenalectomy.

ISSN:0028-3835    

DOI:10.1159/000123016

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Nerve endings (n = 1,298) on noradrenaline cells in adrenal medullas of male rats (n =117) were investigated by quantitative electron microscopy, with sampling at 8 times during a standardized light:dark (12:12) photo-period cycle. Numbers per unit area were determined for synaptic vesicles of two types, small clear vesicles (SCVN) and large granular vesicles (LGVN); from these the percent of LGV per total vesicle number was calculated. In non-operated animals mean SCVN had two cycles per day, with acrophases near the middle of the light and dark phases and troughs near the times of change in lighting; there were also significant peaks (at start and middle of dark phase) and troughs in mean LGVN. Sham-operated (SPX) animals had decreased or insignificant signs of rhythmic changes in these two vesicle types; reduction was most marked in SCVN after SPX. Pinealectomized (PX) differed from non-operated animals in apparent losses of the cyclic changes in SCVN in the dark phase and in LGVN at the start of the dark phase; the former could have been due to a desynchronization of the dark phase rhythm in SCVN in the absence of the pineal. Nerve endings on A-cells and N-cells differed consistently and significantly in the quantitative relations and rhythmic patterns of their two major kinds of synaptic vesicles. These differences, and those seen after pinealectomy or sham surgery, indicate that both the neuroendocr¡ne and preganglionic mechanisms regulating the chromaffin cells have temporal and quantitative characteristics that differ in relation to major type of chromaffin cell affected

ISSN:0028-3835    

DOI:10.1159/000123017

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The neuroendocrine and neurochemical responses of rats to 5 min of cold exposure versus 5 min of forced immobilization were determined and compared. We found that plasma hormones and brain neurochemical systems responded differently to the two different stressors. Plasma prolactin levels were elevated over 10-fold in the immobilized group, while rising only 2-fold in the cold stress group. Levels of corticosterone were significantly increased and growth hormone levels were decreased in both stressed groups as compared to controls. Levels of cyclic GMP were markedly elevated in 11 brain regions following cold exposure. Surprisingly, no elevation of cyclic GMP was found after forced immobilization. Cyclic AMP, norepinephrine. and dopamine levels throughout the 17 regions of brain examined showed no significant response to 5 min of either stressor. Lesions of the ventral medial tegmental area did not affect the cyclic GMP or neuroendocrine responses to cold stress. Lesion of the nucleus locus ceruleus did not affect regional cyclic GMP response but significantly reduced growth hormone levels in the cold-stressed rats.

ISSN:0028-3835    

DOI:10.1159/000123018

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

In the Siberian hamster the pituitary content of bioassayable MSH has been shown to be seasonally variable, being greater during the long days of spring and summer than during the short days of autumn and winter. Similar changes in the pituitary content of both bioassayable MSH and immunoreactive αMSH can be induced by transfer of animals between artificial light photoperiods of appropriate duration

ISSN:0028-3835    

DOI:10.1159/000123019

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Because of the usually low spontaneous activity of oxytocin producing cells, the effect of low frequency (6 Hz) electrical stimulation of the pituitary stalk in vivo upon plasma oxytocin concentration, uterine contractions and intramammary pressure was studied. 30 min of stimulation increased plasma oxytocin concentration. The same type of stimulation elicited both uterine contractions in early post portion rats and milk ejection in the lactating rat, but the latter phenomenon was not considered to mimic physiological events as contrasted with the former. It was concluded that in contrast to previous data, below 10 Hz stimulation of the pituitary stalk in vivo is also effective in producing hormone release and, furthermore, that it may have physiological consequences.

ISSN:0028-3835    

DOI:10.1159/000123020

出版商:S. Karger AG    

年代:1980

数据来源: Karger