Effect of long-term internal irradiation on neurons of the hypothalamic arcuate and suprachiasmatic nuclei and median eminence in rats

1981 ◽  
Vol 91 (6) ◽  
pp. 833-836
Author(s):  
V. I. Dedov
Keyword(s):  
Median Eminence ◽  
Suprachiasmatic Nuclei ◽  
Internal Irradiation

LONG-TERM EFFECTS OF INTRACEREBRAL CORTICOID IMPLANTS

1967 ◽  
Vol 55 (3) ◽  
pp. 440-450 ◽  
Author(s):  
Shaul Feldman ◽  
Nisim Conforti ◽  
Julian M. Davidson
Keyword(s):  
Ascorbic Acid ◽  
Median Eminence ◽  
Adrenal Glands ◽  
Long Term Effects ◽  
Unilateral Adrenalectomy ◽  
Post Operative Period ◽  
Steady Decrease ◽  
Medial Hypothalamus ◽  
Post Implantation

ABSTRACT Chronic implantation of cortisol acetate in the basal medial hypothalamus resulted in a steady decrease in weight of the adrenal glands which remained severely atrophic up to 70 days post-implantation. At this time, however, the adrenal ascorbic acid depletion response to unilateral adrenalectomy was normal. The compensatory adrenal hypertrophy (CAH) response, which was inhibited in the immediate post-operative period, reappeared later, and had returned to normal by 21 days postoperatively. Intramuscular administration of cortisol in unimplanted rats inhibited CAH at 14 or 21 days following onset of treatment, and prevented the recovery of CAH in animals implanted 21 days previously with cortisol in the median eminence. The possibility is discussed that the differential recovery of the responses to unilateral adrenalectomy in implanted animals with continuing atrophy of the adrenal cortex is due to some adaptation of central nervous mechanisms subserving the CAH response.

Mechanism of restoration of ACTH release in rats with long-term lesions of the paraventricular nuclei

1986 ◽  
Vol 111 (1) ◽  
pp. 75-82 ◽  
Author(s):  
J. Dohanics ◽  
G. Kapócs ◽  
T. Janáky ◽  
J. Z. Kiss ◽  
G. Rappay ◽  
...  
Keyword(s):  
Median Eminence ◽  
Plasma Concentrations ◽  
Plasma Acth ◽  
Corticotrophin Releasing Factor ◽  
Paraventricular Nuclei ◽  
Basal Plasma ◽  
Corticosterone Response ◽  
Intact Rats ◽  
Acth Release

ABSTRACT The effects of lesions in the paraventricular nucleus (PVN) on the adrenocortical response to ether stress were investigated in neurohypophysectomized and intact rats. During the first 4 days after placement of lesions in the PVN, the corticosterone response to ether stress was almost completely inhibited. It then gradually increased and, within 4–6 weeks of surgery, was restored to about 60% of that in sham-operated rats. Basal plasma concentrations of corticosterone were low in rats after placement of lesions in the PVN and/or after neurointermediate lobectomy (NILX). Corticosterone responses to ether stress were similar in groups submitted to PVN lesions and/or NILX, and lower than those in the appropriate sham-operated groups. In all lesioned groups, plasma ACTH concentrations after a combination of stressors (ether plus laparotomy) were also lower than those in the sham-operated groups. Six weeks after lesioning of the PVN, immunoreactive rat corticotrophin-releasing factor-41 (rCRF-41) concentrations in stalk-median eminence (SME) extract fell to about 5% of that in sham-operated rats, while immunoreactive arginine vasopressin (AVP) concentrations did not change. Immunohistochemistry revealed a substantial decrease in rCRF-41 immunostaining of the median eminence 6 weeks after lesioning of the PVN, though randomly located clusters of stained terminals were still seen in the whole rostro-caudal extent of the median eminence. A mixture containing synthetic rCRF-41 and AVP, in proportions similar to those in SME extracts from sham-operated rats, caused significantly less release of ACTH from anterior pituitary cell cultures than did SME extracts from sham-operated rats. Extracts of SME from PVN-lesioned rats released as much ACTH as a mixture containing synthetic rCRF-41 and AVP in proportions similar to those in the SME extracts from PVN-lesioned rats. Extracts of SME from either PVN-lesioned or sham-operated rats did not cause a significant increase in the amount of ACTH released when preincubated with antisera to both rCRF-41 and AVP. It is suggested that (1) the restoration of the adrenocortical reponse to ether stress, evident within a few days of placement of lesions in the PVN, occurs independently of neurohypophysial function; (2) the full corticosterone and ACTH response to ether or ether plus laparotomy stress requires not only an intact PVN but also an intact neurointermediate lobe; (3) SME extracts from sham-operated rats contain a factor(s) with the ability to potentiate the ACTHreleasing effect of rCRF-41 and AVP; and (4) the ACTH-releasing activity of SME extract obtained from rats with long-term PVN lesions is probably due to its remaininJ content of rCRF-41 and AVP. J. Endocr. (1986) 111, 75–82

Immunocytochemical changes in hypothalamic and pituitary hormones after acute and prolonged stressful stimuli in the anestrous ewe

1988 ◽  
Vol 118 (2) ◽  
pp. 269-276 ◽  
Author(s):  
Jolanta Polkowska ◽  
Franciszek Przekop
Keyword(s):  
Stress Reduction ◽  
Median Eminence ◽  
Acute Stress ◽  
Secretory Activity ◽  
Cell Types ◽  
Pituitary Hormones ◽  
Slight Reduction ◽  
Beta Endorphin ◽  
Gh Cells

Abstract. We studied the effect of short (acute (20 min/h, for 4 h) and intermittent, long-term (20 min/h for 9 h on 3 consecutive days) electric foot shocks on the immunocytochemical localization of CRH and SRIH in the hypothalamus and of ACTH, beta-endorphin, GH and PRL in the pituitary of the anestrous ewe. Acute stress greatly reduced immunoreactive (ir) CRH in the median eminence and cellular ir ACTH, beta-endorphin and PRL, as well as the proportion of these cell types in the pituitary. A slight reduction of irSRIH in the median eminence was also observed. After long-term stress, reduction of irCRH in the median eminence was still observed. However, ACTH/beta-endorphin cells in the pituitary gland displayed increased secretory activity, manifested by hypertrophy and hyperplasia. A marked depletion of irSRIH in the nerve terminals of the median eminence was observed. The proportion of PRL cells but not their ir content returned to control levels. No effects were observed on the features of the GH cells. This study indicates that there are differences in the effect of short- and long-term stressful stimuli on the activity of hormonal systems in the anestrous ewe. Short-term stress immediately activates the CRH/ACTH/beta-endorphin axis. prolonged stress appears to augment the activation of the SRIH hypothalamic system and probably has a restraining effect on ACTH/beta-endorphin release.

scholarly journals Daily Rhythm of Tryptophan Hydroxylase-2 Messenger Ribonucleic Acid within Raphe Neurons Is Induced by Corticoid Daily Surge and Modulated by Enhanced Locomotor Activity

Endocrinology ◽  
2007 ◽  
Vol 148 (11) ◽  
pp. 5165-5172 ◽  
Author(s):  
Zeina S. Malek ◽  
Dominique Sage ◽  
Paul Pévet ◽  
Sylvie Raison
Keyword(s):  
Locomotor Activity ◽  
Tryptophan Hydroxylase ◽  
Mrna Levels ◽  
Median Raphe ◽  
Suprachiasmatic Nuclei ◽  
Master Clock ◽  
Median Raphé ◽  
Raphe Neurons ◽  
Adrenalectomized Rats

Tryptophan hydroxylase (TPH, the rate-limiting enzyme of serotonin synthesis) protein and mRNA levels display a circadian expression in the rat dorsal and median raphe. These patterns suggest a rhythmic synthesis of serotonin under the control of the master clock of suprachiasmatic nuclei. In the present study, we examined the involvement of endocrine and behavioral output signals of the master clock upon the Tph2 mRNA levels by quantitative in situ hybridization. In the absence of adrenals, a complete suppression of Tph2 mRNA rhythm was observed in dorsal and median raphe over 24 h. The restoration of corticosterone daily variations in adrenalectomized rats induced a Tph2 mRNA rhythmic pattern de novo, indicating that Tph2 mRNA rhythm is dependent upon daily fluctuations of glucocorticoids. Enhanced voluntary locomotor activity during 6 wk increased the level of Tph2 mRNA in both raphe nuclei of control rats without concomitant increase of corticosterone plasma levels. Moreover, this long-term enhanced locomotor activity was able to restore significant variation of Tph2 mRNA in adrenalectomized rats. In conclusion, both endocrine and behavioral cues can modulate Tph2 expression in dorsal and median raphe. The corticosterone surge acts as a rhythmic cue that induces the rhythmic expression of Tph2 in the raphe neurons. On the other hand, long-term exercise modulates the expression levels of this gene. Thus, the serotonin neurons are a target for both endocrine and behavioral circadian cues, and the serotoninergic input to the suprachiasmatic nuclei might feedback and influence the functioning of the clock itself.

INCREASE IN DOPAMINE CONTENT OF THE RAT MEDIAN EMINENCE AFTER LONG-TERM OVARIECTOMY AND ITS REVERSAL BY ESTROGEN REPLACEMENT1

Endocrinology ◽  
1977 ◽  
Vol 101 (6) ◽  
pp. 1894-1897 ◽  
Author(s):  
Gary A. Gudelsky ◽  
Lucio Annunziato ◽  
Kenneth E. Moore
Keyword(s):  
Median Eminence ◽  
Dopamine Content

ABNORMALITIES IN THE SEASONAL COURSE OF OESTROUS CYCLES IN EWES AFTER LESIONS OF THE SUPRACHIASMATIC AREA OF THE HYPOTHALAMUS

1980 ◽  
Vol 85 (3) ◽  
pp. 481-486 ◽  
Author(s):  
F. PRZEKOP ◽  
E. DOMAŃSKI
Keyword(s):  
Breeding Season ◽  
Median Eminence ◽  
Inhibitory Action ◽  
Preoptic Area ◽  
Breeding Period ◽  
Suprachiasmatic Nuclei ◽  
Hypothalamic Area ◽  
Gonadotrophin Releasing Hormone ◽  
Basal Concentration ◽  
Gonadotrophic Cells

The effects of lesions of the suprachiasmatic nuclei (SCN), anterior hypothalamic area (AHA) above the SCN and medial basal hypothalmus (MBH) on oestrous cycles in Merino ewes were observed. Ten animals with lesions of the SCN area continued to have oestrous cycles and ovulations throughout the whole breeding season; in six of these ewes the cycles and ovulations did not stop but were extended into the quiescent non-breeding period. Lesions placed above the SCN in the AHA (three animals) did not affect the oestrous cycles. Together with earlier experiments involving anterior hypothalamic deafferentation rostral and caudal to the SCN, it is suggested that the SCN has a role in transmitting inhibitory action from the medial preoptic area and suppressing the liberation of gonadotrophin-releasing hormone(s) (GnRH) during the non-breeding anoestrous period. Injury to the MBH was followed by cessation of oestrous cycles and of ovulation, a decrease in the number and size of gonadotrophic cells, atrophy of the ovaries and a lowered basal concentration of LH in plasma. This was probably the result of injury to the neurones that produce or transport GnRH to the median eminence.

CHRONIC MEDIAN EMINENCE LESIONS AND OVARIECTOMY: EFFECTS ON FOLLICLE-STIMULATING HORMONE SECRETION IN THE RAT

1971 ◽  
Vol 51 (4) ◽  
pp. 665-674 ◽  
Author(s):  
E. B. CRAMER ◽  
R. E. TRAUM ◽  
S. A. D'ANGELO
Keyword(s):  
Median Eminence ◽  
Follicle Stimulating Hormone ◽  
Hormone Secretion ◽  
Serum Levels ◽  
Ovariectomized Rats ◽  
Adult Rats ◽  
Serum Hormone ◽  
Marked Atrophy ◽  
Stimulating Hormone

SUMMARY Pituitary and serum follicle-stimulating hormone (FSH) concentrations were determined by the Steelman—Pohley ovarian augmentation bioassay method in normal adult rats and in rats subjected to ovariectomy and/or electrolytic lesioning of the tuberal hypothalamus 10, 30 or 90 days previously. Ovariectomy resulted in a rapid, significant increase in FSH concentration of the adenohypophysis. Pituitary FSH concentrations were increased sixfold 10 and 30 days after ovariectomy and by 90 days were increased by 700%. (Hormone stores in the adenohypophysis increased correspondingly.) Serum FSH levels in ovariectomized rats also increased but at a slower rate. Ten days after ovariectomy, serum FSH levels were still normal. Thirty and ninety days postoperatively, serum FSH titres were doubled and quintupled, respectively. Chronic median eminence lesions eventually caused obesity, a marked atrophy of the reproductive system and significant increase in the FSH concentration of the adenohypophysis. Follicle-stimulating hormone was not detected in the sera of rats with short-term lesions but serum hormone levels were in the normal range 30 and 90 days after the lesions were made. Complete destruction of the median eminence in ovariectomized rats was associated with further increase in pituitary FSH concentration and content. Ninety days after simultaneous lesioning and ovariectomy, FSH concentration of the adenohypophysis was almost twice that of the ovariectomized control and the hormone content was about 14 times that in the normal pituitary. In contrast, the raised FSH serum levels observed after long-term ovariectomy were significantly reduced (50%). It is concluded that chronic median eminence lesions which induce obesity and ovarian atrophy in rats differentially affect synthesis and release of FSH by the adenohypophysis.

scholarly journals Age and Long-Term Hormone Treatment Effects on the Ultrastructural Morphology of the Median Eminence of Female Rhesus Macaques

2015 ◽  
Vol 103 (6) ◽  
pp. 650-664 ◽  
Author(s):  
Michelle M. Naugle ◽  
Sateria A. Lozano ◽  
Fay A. Guarraci ◽  
Larry F. Lindsey ◽  
Ji E. Kim ◽  
...  
Keyword(s):  
Median Eminence ◽  
Treatment Effects ◽  
Rhesus Macaques ◽  
Hormone Treatment ◽  
Ultrastructural Morphology ◽  
Female Rhesus ◽  
Female Rhesus Macaques

Short-term but not long-term adrenalectomy modulates amplitude and frequency of the CRH41 episodic release in push—pull cannulated median eminence of free-moving rats

1994 ◽  
Vol 658 (1-2) ◽  
pp. 185-191 ◽  
Author(s):  
G. Ixart ◽  
P. Siaud ◽  
M. Mekaouche ◽  
G. Barbanel ◽  
L. Givalois ◽  
...  
Keyword(s):  
Median Eminence ◽  
Short Term
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