摘要:

Pinealectomy had inconstant effects on serum gonadotropins when blood samples were taken during the day, however late nocturnal titers of both FSH and LH tended to decline and this decline tended to be reversed by pinealectomy. Either anosmia or blinding elevated nocturnal FSH and had a tendency to elevate nocturnal LH titers – effects which were only inconstantly modified by pinealectomy. Blinding plus anosmia lowered both daytime and nocturnal FSH titers; the lowering of nocturnal levels was reversed by pinealectomy. There was a less pronounced lowering of nocturnal LH titers in these doubly-operated animals and again this was partially reversed by pinealectomy. These changes in gonadotropin titers probably accounted at least in part for the testicular atrophy seen in the doubly-operated animals and its reversal by pinealectomy. Following castration, plasma gonadotropin titers rose in all groups and the final level of FSH attained was highest in the pinealectomized animals. Similarly, final levels of FSH and LH were further increased in castrates by blinding, anosmia or blinding plus anosmia, but these changes were not consistently modified by pinealectomy. At sacrifice of the castrates, pituitary FSH and LH concentrations were not modified by pinealectomy, however they were elevated by anosmia or by the double sensory-deprivation. The atrophy of the seminal vesicles induced by castration was partially prevented by pinealectomy, which suggests that the pineal also exerts a direct inhibitory effect on this accessory organ. Alterations in anterior and posterior pituitary weight were also observe

ISSN:0028-3835    

DOI:10.1159/000122431

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The role of the amygdaloid complexes in the compensatory hypersecretion of ACTH following adrenalectomy was studied in the adult male rat. Unilateral or bilateral radiofrequency or knife-cut lesions were placed in the amygdalae, their efferent pathways or the septal region. Three weeks following adrenalectomy resting plasma ACTH concentrations were measured by radioimmunoassay. Bilateral lesions of a direct medial-projecting portion of the ventral amygdalo-hypothalamic pathway blocked the compensatory hypersecretion of ACTH following adrenalectomy. A unilateral complete amygdalar lesion coupled with destruction of the same direct amygdalo-hypothalamic pathway on the opposite side had the same positive effect. In contrast, unilateral destruction of the direct amygdalo-hypothalamic projections, ablation of the septum, or bilateral destruction of the stria terminalis did not block hypersecretion of ACTH following adrenalectomy. These data suggest that the amygdalae and their direct hypothalamic projections, but not the stria terminalis or septum, are essential for the hypersecretion of ACTH following adrenalectomy. Furthermore, one amygdaloid complex appears sufficient for this effect. It is possible that the amygdalae act as a central nervous system ‘glucocorticoid-sensor’ in the modulation of ACTH secretion in the

ISSN:0028-3835    

DOI:10.1159/000122432

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

24 and 28 day old rats, raised in a 14 h light: 10 h dark (14:10) cycle, showed a clear serum corticosterone (B) peak at the beginning of the dark period (18.00 h) with an amplitude of 25–30 µg%. Other B values during the 24 h period were lower (9–12 µg%). Rats raised in a 8.5:15.5 cycle had a B peak (after onset of the dark period, at 22.00 h). Rats raised in constant light (LL) showed no variation in B throughout the 24 h. Weanling rats raised in a 8.5 :15.5 cycle appeared to synchronize more rapidly to a 14:10 cycle than did rats raised in LL. When placed in LL at weaning, rats raised either in 14:10 or 8.5:15.5 had lost their periodicity by day 24. When rats raised in 8.5:15.5 were shifted to LL or 14:10 after weaning age (day 24), the pattern of response was different. One day after the shift, rats placed in a 14:10 cycle displayed a pattern of B synchronized to the normal 14:10 pattern for rats born and raised in that light cycle. This synchrony persisted for at least 3 days. Rats placed in 14:10 at 21 days of age did not show a fully synchronized pattern until day 28. It can be concluded that weanling rats exposed to a light-dark cycle adapt quickly to a new light cycle and that older prepubertal rats shift even more qu

ISSN:0028-3835    

DOI:10.1159/000122433

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Separate regions of the anterior periventricular area (PVA), median eminence (ME) and frontal cortex from brains of hypophysectomized female and intact male rats were extracted and homogenized. The LH-RH content of these homogenates was determined by a specific double antibody radioimmunoassay. LH-RH was found in the PVA as well as in the ME of both hypophysectomized female and intact male rats; it was not detected in the frontal cortex. Extracellular recordings were made from neurons in the PVA and 55 neurons were activated antidromically by stimulating the ME. This suggests that PVA neurons exist with axons terminating in the ME. It is assumed that these axons are unmyelinated since their conduction velocity was approximately 0.3–0.8 m/sec. In addition to the antidromically-activated neurons, 26 neurons with characteristics of transsynaptic activation were recorded in the PVA following stimulation of the ME. Some of the units recorded from the ME-arcuate (ARC) region were also activated either antidromically or transsynaptically by stimulating the PVA. The effect of PVA stimulation on LH release was tested in ovariectomized, estrogen-treated rats with or without anterior deafferentation of the hypothalamus. Increased LH concentration in serum was elicited by PVA stimulation of rats in which deafferentation was either not performed or not completed; no increase in serum LH level was observed following PVA stimulation in rats with complete deafferentation. These data suggest that PVA neurons synthesize LH-RH, which is released at the M

ISSN:0028-3835    

DOI:10.1159/000122434

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Cultured neurohypophysial cells from human fetuses aged 130–155 days release into the culture medium an active principle which has antidiuretic, hydroosmotic and rat uterine activities. The chromatographic mobility of the active principle, as well as the susceptibility of all of the above activities to tryptic digestion, indicates the presence of a basic peptide identical to arginine vasotocin (AVT). The ability of these cultured cells, which are probably ependymal cells, to release the above activities during 43 days of incubation, suggests that AVT is synthesized and secreted by specialized ependymal cells in the developing human neurohypophysis. Neither in the culture media from anterior pituitaries of the same fetuses nor in control culture media could antidiuretic, rat uterine or hydroosmotic activities be detected. Although the nonincubated neurohypophyses of the same age contain pharmacological activities suggesting the presence of vasopressin, oxytocin and AVT, the neurohypophysial cells cultured in vitro apparently release only AVT into the medium. This supports the suggestion that whereas vasopressin and oxytocin are synthesized in the hypothalamic neurosecretory cells, AVT, on the contrary, appears to be synthesized by ependymal neurohypophysial cells in the developing human neurohypophysis. Consequently, the fetal human neurohypophysis, and presumably the fetal mammalian neurohypophysis, appears not only as a storage site for neurohypophysial hormones but also as an endocrine structure which synthesizes and secretes AVT by ependymosecretio

ISSN:0028-3835    

DOI:10.1159/000122435

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

After rats had adapted to regular meal feeding in the morning they demonstrated an altered circadian rhythm of plasma corticosterone (B) even under the normal light-dark cycle. The altered daily rhythm of plasma B consisted of two peaks, with one peak at 08.00 h in anticipation of meal feeding and a second peak corresponding to the normal peak of plasma B prior to lights-off seen in ad libitum-fed animals. Neither peak of plasma B in the meal-fed animals achieved the magnitude of the single peak observed in control animals. In spite of some quantitative differences during certain periods of the day, after the animals had adapted to meal feeding there was no difference in the basic profile of the daily rhythm of plasma immunoactive growth hormone (GH).

ISSN:0028-3835    

DOI:10.1159/000122436

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The immature rat that has been induced to ovulate with pregnant mare serum (PMS) has proven to be a valuable model for the study of antiovulatory compounds. This paper describes an extension of this model in order to attempt to study the site of action of substances such as pentobarbital and a pineal compound, melatonin. A first experiment was designed to define a specific time for injecting pentobarbital in order to inhibit ovulation. In this study immature female rats were given injections with 25 IU PMS; pentobarbital was given at various times after PMS treatment. This study showed that sodium pentobarbital (35 mg/kg, i.p.) inhibits LH release and ovulation when rats have been anesthetized between 2 and 6 p.m. on day 2 after PMS treatment. In a second experiment ovulation was blocked with pentobarbital (35 mg/kg, i.p., beginning at 12 noon and at 2 p.m. on day 2 after PMS treatment) and completely restored to normal with the s.c. injection of 2 µg GnRH at 2 and 4 p.m. on day 2 after PMS treatment. In the third experiment, varying doses of GnRH were studied for their capacity to overcome the pentobarbital block. This study showed that 2 µg, 1 µg, 500 ng, and 250 ng of GnRH at 2 and 4 p.m. on day 2 after PMS treatment were equipotent in causing ovulation. In a fourth experiment ovulation was blocked with melatonin and this block was overcome with exogenous GnRH. In the last study exogenous GnRH was shown to restore ovulation after being blocked by both melatonin and pentobarbital. This evidence suggests that pentobarbital and melatonin inhibit ovulation by inhibiting the secretion of endogenous Gn

ISSN:0028-3835    

DOI:10.1159/000122437

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The activities of the melatonin-forming enzymes hydroxyindole-O-methyl transferase (HIOMT) and N-acetyl transferase (NAT) were determined in pineals of mature female Coturnix quail receiving implants of melatonin (10 µg, 1 µg, 0.1 µg) weekly for 4 weeks. Both HIOMT and NAT were significantly decreased by implants of 10 and 1 µg melatonin compared to vehicle and intact controls. Oviductal weights tended to be higher with increasing quantities of melatonin. These results suggest that melatonin exerts a feedback inhibition upon its synthesizing enzymes which may be of particular importance during the rapid sexual maturation of this spec

ISSN:0028-3835    

DOI:10.1159/000122438

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

To determine whether the circadian rhythm in pituitary-adrenal function is abolished after interruption of neural connections of the medial basal hypothalamus (MBH), corticosterone patterns were examined in individual adult female rats following surgical isolation of the MBH (MBHI rats). Non-stress plasma corticosterone levels were assessed fluorometrically in blood samples obtained from a tail vein of each rat at 4-h intervals for 44 h, 7–8 weeks after surgery. The highest corticosterone levels for most intact and sham-operated controls were obtained in samples collected at the period of light-dark transition. Individual MBHI rats demonstrated steroid excursions of normal amplitude that were not linked with time of day; these patterns appeared asynchronous and devoid of a 24-h cycle. The data indicate that major excursions in plasma corticosterone levels persist following surgical interruption of connections of the MBH, but circadian rhythmicity is abolishe

ISSN:0028-3835    

DOI:10.1159/000122439

出版商:S. Karger AG    

年代:1975

数据来源: Karger