摘要:

Weanling Sprague-Dawley rats received bilateral anodic electrolytic lesions with platinum-iridium (Ptlr) electrodes in the ventromedial (VMN) and dorsomedial (DMN) hypothalamic areas. Sham-operated rats served as controls. The rats were maintained for 48 days (experiment 1) and 33 days (experiment 2) and food intake, body weight (b.w.), nose-tail length and obesity index were recorded. The data of both experiments indicate that all parameters change in the same direction, as they do when lesions are produced with anodic stainless steel electrodes: in the VMN-lesioned animals, b.w. gains and overall mean food intake were normal, carcass fat increased and linear growth was reduced. In experiment 2, however, there was a temporary hyperphagia during the 1st 2 weeks of the study. In the DMN-lesioned rats, both ponderal and linear growth and food intake were decreased but body composition was normal. Plasma obtained at sacrifice in experiment 2 showed slight but significant hyperinsulinemia in the VMN rats (p < 0.02 vs control and p < 0.05 vs DMN rats). Prolactin (PRL) levels, on the other hand, were higher in the DMN-lesioned rats (p<0.05 vs control and p<0.02 vs VMN rats). The data indicate that the changes characteristic of the weanling rat VMN and DMN syndromes are due to ‘true’ tissue destruction rather than to artifactitious side effects of the lesions. They also suggest, therefore, that an ‘irritative focus’ hypothesis is not required to account for the observed alterations. They further suggest that the DMN may play a role in the control of PRL

ISSN:0028-3835    

DOI:10.1159/000122615

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The daily s.c. injection of 25 µg melatonin (MEL) in oil into adult male hamsters at 7 p.m. (lights on 6 a.m. to 8 p.m.) for 50 days caused involution of the testes, coagulation of glands and seminal vesicles and depression in pituitary prolactin (Prl) levels. Similar injections of MEL given at 9 a.m. completely failed to cause regression of the sex organs or a depression in pituitary Prl levels. Injections of MEL in the p.m. were completely ineffective in inhibiting either the growth of the gonads and adnexa or the pituitary Prl levels if the animals had been pinealectomized. Likewise, superior cervical ganglionectomy, decentralization of the superior cervical ganglia and anterior hypothalamic deafferetation, procedures which interfere with the sympathetic nerve supply to the pineal gland, negated the ability of p.m. MEL injections to inhibit reproduction in male hamsters. The results indicate that daily MEL injections are capable of suppressing reproductive physiology in male hamsters, but only when the indole is injected late in the light period, in this case, 13 h after lights on. The findings also illustrate that daily p.m. MEL injections can inhibit reproduction only in animals that have an intact and sympathetically innervated pineal gland

ISSN:0028-3835    

DOI:10.1159/000122616

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Three enzymes selected as representative of major metabolic pathways (malic dehydrogenase, of the citric acid cycle, lactic dehydrogenase, of glycolysis and glucose-6-phosphate dehydrogenase, of the pentose pathway) were measured by quantitative histochemical methods in individual hypothalamic nuclei during the 5-day estrous cycle of adult rats. Malic dehydrogenase increases significantly from low proestrous levels to a peak at estrus and then declines during diestrus in the following nuclei and areas of the anterior hypothalamus: medial and lateral preoptic, suprachiasmatic, supraoptic, and anterior. Significant peaks of lactic dehydrogenase occur more often during diestrus-3 in hypothalamic nuclei of the middle and posterior hypothalamus. Glucose-6-ρhosphate dehydrogenase has a biphasic pattern with peaks usually occurring during the diestrous period

ISSN:0028-3835    

DOI:10.1159/000122617

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Stereological analysis of the secretory cells of the pars intermedia of Xenopus laevis over a period of 3 days following the transfer of animals from a white to a black background has revealed that significant alterations in the ultrastructural appearance of these cells can be detected 8 h after the transfer. In particular, changes in the secretory granules and the rough endoplasmic reticulum were found to correlate well with previous reports concerning the melanocyte-stimulating hormone (MSH) content and the capacity for protein synthesis of the pars intermedia.

ISSN:0028-3835    

DOI:10.1159/000122619

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Day length or photoperiod is an important determinant of seasonal breeding or sexual maturation in the vole (Microtus agrestis). Exposure of voles to short (6 h) photoperiods slows gonadal development or causes active gonads to regress. Abolishing pineal activity either by chemical sympathectomy, using 6-hydroxydopamine (6-OHDA), or by surgical pinealectomy, prevents this inhibiting or regressing effect of short photoperiod upon gonads. Thus, the pineal gland appears to play a part in the measurement of day length by voles and in the physiological causation of their seasonal breeding.

ISSN:0028-3835    

DOI:10.1159/000122620

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Rats reared in an 8 h light, 16 h dark photoperiod (8:16) exhibit an evening peak of serum corticosterone at 22.00 h colony time. When exposed to a new test cycle of 14:10, the animals first show a blunted peak at 18.00 h and 22.00 h and then a clear peak at 18.00 h with loss of the 22.00 h peak. In this study, rats 30 days of age were ovariectomized during the challenge of a new light-dark cycle (14:10) to determine whether the ovaries were necessary for the adaptation of the peripheral corticosterone rhythm prior to puberty in response to a photoperiod challenge. At 31 days of age, all three groups (intact, sham-operated and gonadectomized on day 30) exhibited elevated corticosterone levels at 14.00 through 22.00 h which fell to somewhat lower values in the morning of day 32. The intact groups showed a peak at 18.00 h on day 32 while the other two groups had a less defined elevation in corticosterone in the evening persisting through 22.00 h. All three groups showed a clearcut fall at 02.00 h and 06.00 h on day 33. On day 35, intact and gonadectomized (OVX) rats showed similar patterns and levels of corticosterone, but both higher amplitude and elevated daytime values were observed in the sham-operated group. The latter animals were undergoing puberty (vaginal opening, day 34–35) while the other two groups were still prepuberal. In the OVX rats, the peak of serum corticosterone was observed at 22.00 h 10 and 20 days after surgery. Intact and sham-operated controls retained a peak at 18.00 h. Adults ovariectomized after puberty showed a reduction in daily corticosterone levels but did not exhibit a phase shift once the peak emerged at 18.00 h. It can be concluded that either sham surgery or ovariectomy performed on day 30 can partially disrupt the rephasing of the serum corticosterone rhythm in prepuberal rats, but that the pattern quickly normalizes. This suggests that the ovaries are not necessary for the emergence of a phase shift in response to a change from a short day (8:16) to a long day (14:10) cycle. However, maintenance of the phase of the corticosterone rhythm in the new cycle does depend upon ovarian secretion in rats ovariectomized before puberty, but not in adult rat

ISSN:0028-3835    

DOI:10.1159/000122621

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Effects of intiaventricular infusions of LH-RH and norepinephrine (NE) on the electrical activity of the arcuate nucleus were investigated in normally cycling proestrous rats. Under urethane anesthesia, recordings were made of amplitude-discriminated multiple unit spike activity and integrated multiunit activity (MUA) in parallel with cortical EEC Control infusions of saline (2 µl, isotonic, pH 5.5) were ineffectual, but LH-RH (0.5 µg) induced a significant increase in both multiunit spike activity and integrated MUA. While the response appeared to be continuous, statistical analysis revealed 2 phases: a quick rise which persisted for approximately 5 min, followed 15 min later by a longer-lasting elevation in activity. The onset of the 2nd increase corresponded with the attainment of peak values of pituitary LH output. Subsequent treatment with 20 µg NE, on the other hand, resulted in a marked depression of activity. The fact that NE depresses arcuate neuronal activity at dose levels which cause the release of LH and that LH-RH increases activity within the same population of neurons, while possibly mediating an ‘ultrashort-loop’ negative feedback effect, suggests that this responsive component of the arcuate nucleus, perhaps the tuberoinfundibular dopaminergic system of neurons, is inhibitory to LH r

ISSN:0028-3835    

DOI:10.1159/000122622

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Multiple unit activity (MUA) was obtained from various forebrain regions in unanesthetized, unrestrained resting pigeons throughout the whole photoperiod and compared with plasma corticosterone levels. The pattern of electrical activity recorded from the adrenocorticotropic area of the hypothalamus showed diurnal variations which paralleled the plasma corticosterone fluctuations during the 24 h photoperiod. Both parameters were low in the late afternoon and the evening and high in the early morning. Hypothalamic activation slightly preceded the peak of corticosteronemia. Conversely, in hippocampal (H) and septal (S) regions, the peak of MUA occurred in phase opposition with respect to the hypothalamic peak, and there was a marked decrease of firing rates at the moment when adrenocorticotropic activation was initiated.

ISSN:0028-3835    

DOI:10.1159/000122623

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Hypophysectomized rats bearing grafts of the pars intermedia (PI) in the kidney capsule for 20 days did not show adrenal weights significantly different from those of hypophysectomized controls. Plasma corticosterone was undetectable in the grafted rats, even after the injection of lysine-vasopressin or histamine. On the other hand, MSH activity was present in measurable amounts, independent of the drug administered, in the plasma of the grafted rats. These results suggest that PI transplants do not have the ability to release ACTH, even though it has been previously reported that they contain this hormone.

ISSN:0028-3835    

DOI:10.1159/000122624

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Metyrapone (MET) inhibition of hydrocortisone (3H-HC) uptake and binding in the cytosol and nucleus of various brain regions of the pig was demonstrated in vivo. The hippocampus, hypothalamus and septum were the regions most sensitive to the inhibition by MET. The hippocampus exhibited the greatest reduction in 3H-HC concentration in whole homogenate, bound in cytosol and in nuclei. The anterior pituitary and cerebral cortex were the least sensitive to MET. In vitro incubation of hypothalami with 3H-HC and MET substantiated the results obtained in vivo with regard to the inhibitory action of MET on 3H-HC uptake and binding. These results were interpreted to indicate that MET may act directly in certain brain regions and that this inhibitory action has important implications for both experimental and clinical uses of this drug.

ISSN:0028-3835    

DOI:10.1159/000122625

出版商:S. Karger AG    

年代:1976

数据来源: Karger