摘要:

The purpose of this study was to determine whether the sequence of changes that occur in the adrenal rhythm in maturing female rats (development of a peak, shift in acrophase and amplitude) requires experience with a photoperiodic stimulus or a change in ovarian status. The emergence of the serum corticosterone (CS) rhythm occured more quickly in adult rats placed in a 14 h light, 10 h dark (14:10) cycle at 50 days of age after rearing in constant light (LL) than in weanling rats placed in 14:10. Ovariectomy at weaning age did not alter the pattern of CS development in 14:10 although the amplitude of the peak was reduced even in 25-day-old rats. Adult rats reared in 14:10 held a population rhythm of CS longer after they were placed in LL than did weanling rats placed in LL. This difference was not dependent upon the presence of the ovaries since acutely and chronically ovariectomized (OVX) adult rats responded in a similar manner to adult controls. It can be concluded that the adrenal rhythm emerges as a function of age rather than as a result of a change in ovarian status. The capacity to synchronize serum CS to light-dark cycles develops in the absence of photoperiodic cues.

ISSN:0028-3835    

DOI:10.1159/000122802

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

After the combined treatment with dexamethasone, morphine and pento-barbitone, the electrical stimulation in the rat tuber cinereum induces a rise in plasma corticosterone (CS) level, probably by direct stimulation of the corticoliberin-producing neural elements and the consecutive ACTH release. We have attempted to locate these corticoliberin-containing neural elements by electrical stimulation in rats with various surgical cuts (deafferentations) around the medial basal hypothalamus (MBH). Seven to eight days after the complete circumsection of the MBH, the electrical stimulation of the isolated region did not affect plasma CS level. Also, the electrical excitation proved to be ineffective after antero-lateral or only lateral sections that interrupted the fibers running through the lateral region of the retrochiasmatic area. In contrast, a rise in CS level followed electrical stimulation of rats with anterolateral transections, provided the basal part of the lateral retrochiasmatic area stayed intact. We suggest that fibers traversing the basal region of the lateral retrochiasmatic area have a major role in the release of corticoliberin from the median eminence (ME).

ISSN:0028-3835    

DOI:10.1159/000122803

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Plasma ACTH concentrations were determined in neonatal rats 1, 7, 14, and 21 days old, subjected to treatment with either a median eminence extract with corticotropin releasing factor (CRF) activity or to ether exposure. ‘CRF’ injection elevated plasma ACTH levels on all days tested. Ether exposure elevated ACTH levels on days 14 and 21, but not on days 1 or 7. These results indicate: (1) that there is no diminution of responsiveness of the pituitary to direct stimulation by CRF as a function of age, and (2) that the mediators of the stress response above the level of the pituitary are not functionally mature until approximately day 14. Correlations with previous studies also indicate that there is a delay in the return of adrenal responsiveness until some time after these mediators attain matur

ISSN:0028-3835    

DOI:10.1159/000122804

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

To determine whether adrenocortical function influences rhythmic gonadotropin patterns in male rats, blood samples were obtained by rapid decapitation from control and adrenalectomized male rats at 3-h intervals over a 24-h period (14 h light/day, 4 a.m.–6 p.m.). Control animals showed periodicity in serum LH, prolactin (Prl) and corticosterone similar to that reported previously. Peak and trough serum levels of corticosterone and Prl occurred at 5 p.m. and 8 a.m. respectively whereas those for LH occurred at 11 p.m. and 11 a.m. Serum FSH levels did not vary with circadian periodicity. 15 days after adrenalectomy, serum LH levels continued to fluctuate with a circadian periodicity but showed a marked phase shift; peak LH levels were observed at 8 a.m. The absence of adrenal hormones did not result in altered FSH levels nor was the phase of the Prl rhythm significantly altere

ISSN:0028-3835    

DOI:10.1159/000122805

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Prolactin (Prl) responses to anesthetics, stress of immobilization, and agents that block adrenergic receptors were determined in 13 female rhesus monkeys. The local anesthetic (lidocaine HC1) had no effect, but the general anesthetics (ketamine HC1 and sodium pentobarbital) significantly increased serum Prl levels in intact animals. There was no indication of a pentobarbital-induced inhibition of Prl secretion as reported for other species. A combination of halothane anesthesia and immobilization for 30 or 60 min produced significantly greater increases in Prl levels than immobilization alone for similar periods of time. Prl responses to blockers of adrenergic receptors varied in chair-adapted ovariectomized monkeys. The increase in serum Prl concentrations produced by the β-receptor blocker propranolol was less marked than that induced by the α-receptor blockers phentolamine and phenoxybenzamine. Prl elevations of the highest magnitude and longest duration were produced by haloperidol, which blocks both adrenergic and dopaminergic receptors. Pretreatment of these animals with estradio1-17β had no effect on Prl responses to phentolamine and haloperidol. These results indicate involvement of an adrenergic neurotransmitter system in the control of Prl secretion in primat

ISSN:0028-3835    

DOI:10.1159/000122806

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The development of gonadotrophs in newborn Sprague-Dawley rats subjected to a hypophysial stalk section (SS) by an electrical cauterization of the infundibulum of the hypothalamus was examined throughout the first 12 postnatal days. The electrical cauterization of the infundibulum was performed during 24 to 30 h after birth, and the pituitaries were studied by immunohistochemical procedures 11 days later. In several animals orchiectomy or an administration of testosterone propionate (TP) was performed simultaneously with the cauterization. The SS animals showed remarkable retardation in body growth and in pituitary development. In males the development of gonadotrophs was strongly suppressed in number and in size after the cauterization, whereas in females the suppression was less prominent. Orchiectomy promoted the development of gonadotrophs in the SS males, while TP administration suppressed it in the SS females. These findings indicate that there is sexual difference in the neonatal development of gonadotrophs even in the pituitary isolated from the hypothalamus and that testosterone inhibits the development of gonadotrophs at the level of the hypophysis during the neonatal period in rats.

ISSN:0028-3835    

DOI:10.1159/000122807

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Brief episodes of apparently unprovoked tachycardia (increased heart rate, HR) lasting about 10–20 min were observed about one h after initiation of experimentation in 10 ovariectomized ewes which were fitted with indwelling vascular cannulae. The incidence of tachycardia episodes varied among ewes, but 99 of 215 (46%) sampling trials contained such an episode (mean HR increase = 34 beats/min). Approximately 30–40 min after maximum tachycardia when HR had returned to basal rates, both plasma prolactin (Prl) and growth hormone (GH) increased significantly from the nadir concentrations that had been observed around the time of maximum tachycardia and shortly thereafter. There were no changes in packed cell volume (PCV) and only brief changes in mean arterial blood pressure related to the tachycardia. There was a mild trembling behavior associated with many of the tachycardia episodes. The causes for the tachycardia are not known. Heparin administration did not seem to be involved, but physical stimulation inside the jugular vein, while not essential, may increase the incidence of tachycardia episo

ISSN:0028-3835    

DOI:10.1159/000122808

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

These experiments were designed to study the effects of age of blinding on the circadian rhythm in pituitary-adrenal function in female rats. In the 1st experiment, the eyes were removed at 1 day of age and serial blood samples were obtained at 6-h intervals for 24 h at 45 days. In the 2nd experiment, rats were blinded at 1, 26 or 60 days of age, and serial blood samples were collected at 4-h intervals for 44 h when the rats were 84, 112 and 142 days of age. Intact and sham-operated rats served as controls. Plasma corticosterone (cpd B) concentrations, measured πuorometrically, were used to assess pituitary-adrenal function. Blinding disrupted cpd B patterns in all groups on all occasions. However, steroid patterns of individual rats suggested the presence of free-running 24-h rhythms. This suggestion was supported by the results of aligning the steroid peaks of individual blinded rats. This procedure yielded group patterns of steroid levels which were comparable to those of controls. The periodic stimuli available to the blinded rats from intact rats in the same and adjacent cages did not synchronize this rhythm. These results suggest that the eyes and their central projections are not essential after birth for the development and maintenance of rhythmic pituitary-adrenal function; these structures appear necessary, however, for synchronization with light-dark cycles

ISSN:0028-3835    

DOI:10.1159/000122809

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Steady state levels of serotonin (5HT) in several hypothalamic nuclei of male rats increased when measured 7 days after castration. This effect was reversed by the administration of testosterone propionate (TP). 5HT content of the caudate nucleus, hippocampus and amygdala were measured in castrated rats and in castrated rats which received TP. No change in content was measured.

ISSN:0028-3835    

DOI:10.1159/000122810

出版商:S. Karger AG    

年代:1978

数据来源: Karger