摘要:

The effect of constant light on the age at onset of persistent estrus was compared in rats exposed to constant light since birth (LL-0) and those exposed beginning at 70 days of age (LL-70). Persistent estrus occurred about 27 days later in the LL-0 rats than in the LL-70 rats. Exposure to LL for just the 1st 15 days of life (LL-0-15) and then subsequent exposure to LL at 71 days also delayed the induction of persistent estrus. Neonatal injection of a Harderian gland (HG) homogenate to LL-0–15 rats reduced the age of vaginal opening and 1st estrus and reduced the delayed onset of persistent estrus caused by the neonatal LL. Harderianectomy of LL-0 or hematoporphyrin injections in LL-0–15 rats had no effect on the onset of LL-induced persistent est

ISSN:0028-3835    

DOI:10.1159/000122812

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The effects of pentobarbital (PBTL) on pulsatile LH release in ovariectomized rats were studied and characterized. Unanesthetized rats were first bled continuously (50 μl whole blood every 5–6 min) through indwelling right atrial cannulae for 1½ h prior to PBTL injection (35 mg/kg). Animals were then bled for various periods of time during PBTL-induced anesthesia, as well as for 1½–2 h after recovery of the ½ righting reflex. Whole blood was analyzed for LH by radioimmunoassay. PBTL administration initially inhibited pulsatile LH release for 1¼–1½ h, after which episodic release resumed. For the remaining duration of anesthesia (3–3½ h) episodic LH release was characterized by decreased mean blood LH levels, a decreased rate and magnitude of increase in blood LH levels for individual episodes, and a lengthened periodicity between pulses. However, though reduced, episodic LH release remained stable despite the continued influence of anesthesia. In the 1½–2 h following recovery of the ½ righting reflex, only the periodicity of LH release returned to a pre-anesthesia interval. Mean blood LH levels and the rate at which blood LH levels changed during individual pulses remained reduced, and a slight fall occurred in the extent of the increase in blood LH levels during single LH episodes. The influence of PBTL on those brain regions responsible for controlling pulsatile LH release is therefore of longer duration than the effects of this anesthetic on central nervous system (CNS) areas, which when affected, results in loss of the

ISSN:0028-3835    

DOI:10.1159/000122813

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

In a study of pineal gland influences on hormone secretory profiles, blood samples were collected at 20 min intervals for 26 h from 4 pinealectomized and 4 sham-operated rams which were subjected to a 14.5 h daily photoperiod. Plasma levels of luteinizing hormone (LH) and testosterone (T) underwent rapid pulsatile fluctuations in all rams. Pinealectomized rams produced more LH than the sham-operated rams and a similar trend was recorded for plasma T data, since T secretion closely followed that of LH. A nocturnal elevation of plasma prolactin (Prl) levels displayed by sham-operated rams was substantially abolished by pinealectomy. Also a rise in cortisol secretion during the morning hours recorded from 3 of the sham-operated rams was absent in 2 of the pinealectomized rams. The possible significance of the pineal gland in the regulation of secretion of these hormones is discussed.

ISSN:0028-3835    

DOI:10.1159/000122814

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

A series of experiments were designed to test the assumption that neuro-regulatory mechanisms associated with pituitary ACTH and melanotropin (MSH) secretions are interdependent. Stress elevates both ACTH and MSH activity in mouse pituitaries. There are nervous influences on the secretion of both of these hormones. We have undertaken to stimulate or block various components of the nervous control of these 2 hormones in order to determine whether the 2 are controlled by the same mechanisms or separate ones. We have exposed mice to neurotransmitter blocking agents against serotonin, norepinephrine and epinephrine – parachlorophenylalanine (PCPA), alpha-methyltyrosine (MT), propranolol – both with and without stress. Unilateral adrenalectomy with and without hydrocortisone replacement therapy were investigated. We found that none of the neuro-active substances altered stress elevation of ACTH and MSH. Unilaterally adrenalectomized stressed animals treated with hydrocortisone showed elevated pituitary MSH levels but non increased ACTH release, as measured by size of the remaining adrenal. Adrenalectomy of animals without replacement therapy showed both elevated pituitary MSH and increased ACTH activity Since the ACTH and MSH activity behave independently in the last described experiments, we conclude that ACTH and MSH are independently control

ISSN:0028-3835    

DOI:10.1159/000122815

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The intraperitoneal (i.p.) administration of sodium pentobarbital (30 mg/kg) to long-term ovariectomized adult rats results in a prolonged depression of serum LH levels and in a biphasic decrease of serum prolactin (Prl) titers, but does not modify serum levels of FSH. Consequently, caution should be used when interpretating neuroendocrine results obtained in animals submitted to pentobarbital anesthesia.

ISSN:0028-3835    

DOI:10.1159/000122816

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Adult female ARS/Sprague-Dawley rats were allowed to acclimatize to a a lighting schedule of 12L:12D (LD) for 5 weeks. At that time, half the animals were adrenalectomized, and all rats remained in LD for an additional 4 to 5 weeks. Subsequently, half of the control and half of the adrenalectomized rats were exposed to constant light (LL) for an additional 8 weeks, at which time all animals were sacrificed. Operated rats with regenerated adrenal tissue, determined either by macroscopic examination or serum corticosterone assay (about 50% of the rats), were excluded from all data calculations. Acute disturbances of estrous cycle length were minor. The long-term effects revealed a significant increase in 5-day cycles among the adrenalectomized rats, although the majority of cycles recorded (80%) were still 4 days in length. None of the rats in LD showed spontaneous persistent estrus. Adrenalectomy did not affect the number of ova shed. When placed in LL, the adrenalectomized rats continued to cycle longer than the un-operated controls, but all rats showed persistent estrus (5 or more consecutive days of vaginal cornification) within 7–8 weeks. Adrenalectomized rats had significantly higher body weights than controls. Relative uterine weight was decreased in these animals in both lighting regimens but only reached statistical significance in LD. Ovarian weight, by contrast, was significantly increased among adrenalectomized rats in LD but was identical in both groups in LL. Adrenal weight of intact rats was not altered by LL. Since estrous cycles can continue for at least 3 months in the absence of the adrenal gland, the persistent estrus that occurs in LL is not merely due to the loss of a diurnal rhythm of corticosteroids. Indeed, when adrenalectomized rats are placed in LL, they continue to show estrous cycles longer than do intact rats. Adrenalectomy does appear to increase the length of the cycle in some animals, and the hormonal basis for this warrants further stud

ISSN:0028-3835    

DOI:10.1159/000122817

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Plasma modifications of adenohypophyseal hormones were investigated in groups of female and male rats stressed for 15, 30 min, 1, 2, 4 or 6 h, either by cold (4°C), forced muscular exercise (FME), or immobilization. GH levels in both female and male rats were consistently decreased by the 3 stressing agents. Immobilization in the female and the 3 stressors in the male elicited an early secretory response of prolactin (Prl), while only in immobilized female rats plasma LH levels showed an early, short-lived increment. A more prolonged exposure to stress had an inhibitory influence on plasma Prl and LH levels in both sexes. FSH concentrations were not modified in females, but were decreased in male rats submitted to either one of the 3 stressors. In both male and female rats plasma TSH levels rose during cold exposure, while they were decreased by FME and by immobilization. Our data indicate that the character of the hormonal secretory response during stress is nonspecific. Indeed, to the exception of the specific stimulation of TSH release by cold, stress-induced hormonal changes are not related to the nature but rather to the intensity and duration of the stressing agent

ISSN:0028-3835    

DOI:10.1159/000122818

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The possible role of a neural mechanism involved in the development of compensatory ovarian hypertrophy has been studied. A new technique, the use of a special plastic capsule, has been developed to allow chronic local treatment of the ovary. Local treatment of one of the ovaries with 6-hydroxydopamine (6-OHDA) resulted in a weight increase in the other ovary. In the unilaterally ovariectomized rat the local application of 6-OHDA on the ovary blocked the development of compensatory ovarian hypertrophy. Local treatment of the ovary with dopamine (DA) did not interfere with the compensatory ovarian growth of the other ovary. Data suggest that intact adrenergic afferent and efferent neural elements of the ovary are required for the development of compensatory ovarian hypertrophy.

ISSN:0028-3835    

DOI:10.1159/000122819

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Plasma prolactin (Prl) titers were determined by radioimmunoassay in conscious, freely moving male rats which had either had sham operations or had been pineal-ectomized. Values were determined during the day and during the night in animals on a reversed light cycle. During the day plasma Prl levels were low in both groups with small bursts and a tendency for greater elevation toward the end of the collection period at 17.00 and 18.00 h. There were only 2 significant effects of pinealectomy on these daytime values, one of which was a reduction in the elevation of Prl at 17.30 h. There were also more frequent very low values, less than 5 ng/ml, after pinealectomy. At night there was greater variation of plasma Prl in sham-operated rats and in general the animals showed a sudden elevation just prior to the time the lights were turned on. The values remained elevated for some time thereafter. After pinealectomy the elevation when the lights were turned on was slightly delayed and the responses were smaller in magnitude or even absent. There were significantly more high Prl values in the controls than in the pinealectomized animals in darkness and the area under the curve of Prl release, which was greater at night than in the daytime, was significantly lowered by pinealectomy.

ISSN:0028-3835    

DOI:10.1159/000122820

出版商:S. Karger AG    

年代:1978

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122821

出版商:S. Karger AG    

年代:1978

数据来源: Karger