摘要:

Blood samples were removed via chronic intra-atrial cannulae every 15 min in female rats during the estrous cycle, the last week of pregnancy, parturition and suckling. Growth hormone (GH) secretion during the estrous cycle is characterized by episodic release, occurring approximately once hourly. The surges in GH increase during the last 3–4 days of gestation, and rise to high levels during delivery and with suckling. Prolactin (PRL) shows minimal fluctuations during the estrous cycle, except for a prominent pulsatile surge during proestrus. PRL rises 4–6 h prior to parturition and declines during delivery. These studies provide a basis for further studies on the dynamics of GH and PRL secretion in the female

ISSN:0028-3835    

DOI:10.1159/000122525

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The Inactivation of the hypothalamic hormone by rat liver and kidney homogenates was studied, using specific radioimmunoassays for the measurement of thyrotropin releasing hormone, pGlu-His-Pro-NH2 (TRH), and for an analogous peptide, pGlu-His-Pro-OH (TRH-OH), which has been proposed as a major metabolite of TRH [Nair et al., 1971]. The inactivation of TRH and the free acid was found to be rapid. Heat lability and saturation kinetics suggest the involvement of enzymatic processes. In liver homogenate, TRH-OH production from TRH was observed. The accumulation of TRH-OH was substantial in experiments employing near-saturation concentrations of TRH. The liver and kidney are ascribed as major sites for breakdown of TRH in vivo.

ISSN:0028-3835    

DOI:10.1159/000122606

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Plasma ACTH and corticosterone were measured under basal conditions and after ether or tourniquet stress during the nadir (a.m.) and zenith (p.m.) of the nycterohemeral pituitary-adrenal cycle. Exogenous ACTH was also given at these 2 times to assess adrenal sensitivity to ACTH and the maximal adrenal capacity for corticosterone secretion. Ether stress caused a greater rise in plasma ACTH in the a.m. than in the p.m., even though basal plasma ACTH and corticosterone concentrations were lower in the a.m. than in the p.m. When given in the p.m., pentobarbital anesthesia depressed plasma corticosterone and ACTH to the a.m. level; under these conditions, the rise in plasma ACTH produced by tourniquet stress was the same in the a.m. and p.m. Both tourniquet and ether stresses caused maximal activation of adrenal corticosterone secretion, but ether produced a much greater rise in plasma ACTH. It is concluded that: the greater ether-induced rise in plasma ACTH in the a.m. than in the p.m. is probably due to the lower plasma (and probably tissue) corticosterone concentration at that time; the plasma ACTH concentration for inducing maximal adrenal activation is relatively low; and (3) the higher basal levels of plasma corticosterone in the p.m. than in the a.m. are due to a slight increase in basal ACTH secretion in the p.m.

ISSN:0028-3835    

DOI:10.1159/000122526

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The purpose of this study was to determine whether exposure to a cycle of light and dark before the onset of the adrenal rhythm would be necessary in order for rats to develop a normal rhythm of peripheral corticosterone when placed in a test photoperiod at weaning age. Rats were reared in constant light (LL) until weaning age, at which time they were placed in a cycle of 14 h light, 10 h dark (14:10). Females born and reared in 14:10 had peak corticosterone values at 14.00 h on days 22 and 26, and at 18.00 h on days 32 and 36. Males did not display a clear-cut rhythm at 22 or 26 days but had peak corticosterone at 18.00 h on days 32 and 36. Males and females reared in LL until weaning had no rhythm as a group in 14:10 at 24 days of age, but had a corticosterone peak at 18.00 h on days 28 and 40. Females born and reared in LL and exposed to 14:10 for 1 day developed an adrenal rhythm regardless of the age at exposure, but only 25 day old animals showed a normal pattern for their age group. Puberty was advanced in rats exposed to a single day of 14:10 at 25 days of age, but was delayed in younger rats (22 days old), and was unaffected by light exposure in older rats (28 days of age). It can be concluded that early exposure to light-dark cycles is not required for the normal development of an adrenal rhythm in the weanling rat, and that the setting of the corticosterone rhythm to the photoperiod can occur quite rapidly. Rats at 25-26 days of age are able to respond differently to a light cycle challenge than younger rats. A photoperiodic stimulus at that time can advance the onset of puberty.

ISSN:0028-3835    

DOI:10.1159/000122527

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The rates of synthesis of norepinephrine (NE) and dopamine (DA) in several regions of the hypothalamus have been estimated after exposure of rats to stresses that increase ACTH secretion. The rate of 3H-NE and 3H-DA accumulation from 3H-tyrosine in vitro was used as an index of catecholamine synthesis rates. Exposure to ether vapor, 30 min of cold environment, or laparotomy increased ACTH secretion significantly, as indicated by plasma corticosterone levels. However, only the ether stress affected hypothalamic catecholamines; both NE and DA synthesis rates were increased in the arcuate nucleus area (ANA), but not in the median eminence (ME) or the residual hypothalamus (RH). Dexamethasone treatment blocked the stress-induced ACTH secretion, but had no affect on basal or stress-induced rates of amine synthesis. It is concluded that catecholamines in the ANA participate in mediating ether stress-induced ACTH secretion.

ISSN:0028-3835    

DOI:10.1159/000122528

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Nuclear volumes (NV) of neurons in the preoptic area (POA), suprachiasmatic nucleus (SC), paraventricular nucleus (PVN), supraoptic nucleus (SO), anterior hypothalamic area (AHA), arcuate nucleus (ARN), ventromedial nucleus (VMN), dorso-medial nucleus (DMN) and lateral mammillary nucleus (ML) were measured in 3.5- to 5-month-old female and male rats and in old female and male rats over 22 months of age. Young adult female rats had larger NV than males in the neurons of all measured areas except for the SC during estrus and the ARN. NV of the hypothalamic neurons of female rats decreased in old age in all measured areas except for the VMN of rats exhibiting prolonged vaginal cornification (PVC). Old male rats showed decreased NV only in the neurons of the SC, SO and ML. The extent of NV decrease of the hypothalamic neurons was not similar in different areas. The sexual difference in neuronal NV in most of the areas disappeared in old age. Only the POA of rats with PVC and the ML of old female rats had larger NV than those of old male rats.

ISSN:0028-3835    

DOI:10.1159/000122529

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Plasma from normal human subjects was subjected to a 3-phase methanol extraction. An increase in prolactin release from rat anterior pituitary tissue in vitro obtained with increasing doses of the plasma extract, while no increase in TSH release occurred. Control studies with an extract of simulated plasma using incubation medium with human serum albumin resulted in less release than a comparable plasma extract dose. The plasma extract did not lose activity with heating to 100°C for 10 min, and incubation of normal plasma at 37 °C for 4 h prior to methanol extraction resulted in no loss of prolactin releasing activity. The plasma extract was subjected to cascade ultra-filtration through UM-10, UM-2, and UM-0.5 filters with no significant loss of prolactin releasing activity. Finally, the extract contained no TRH immunoreactivity. These results support the existence of a heat stable, ultra-filterable circulating PRF in human plasma. The origin of this material is unknow

ISSN:0028-3835    

DOI:10.1159/000122530

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The metabolism of striatum dopamine (DA) was studied in mice during proestrus, estrus and diestrus. The following results have been obtained: (1) the concentration of DA is higher in diestrus than in proestrus and estrus; (2) the concentration of its metabolite, homovanillic acid (HVA), is maximum in the estrus phase; (3) the DA turnover, evaluated by measuring the DA disappearance after blocking synthesis with methyl-tyrosine, is faster in estrus than in the other phases. These results have been discussed in view of the possible role of dopaminergic mechanisms in the control of gonadotropin secretion.

ISSN:0028-3835    

DOI:10.1159/000122531

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

I.v. injection of sulpiride (S; 0.5–20 µg/100 g b.w.) caused a significant and dose-related increase in plasma prolactin (Prl) levels in urethane-anesthetized rats, with peak values occuring 10 min after the injection. L-dopa administration (2 mg/100 g b.w., i.v.) significantly blunted plasma Prl response to S (1 µg/100 g b.w., i.v.). S injection (1 µg/rat) into a lateral ventricle also raised plasma Prl significantly. Hypothalamic destruction resulted in a prominent increase of basal plasma Prl, which increased further following the injection of S. These results suggest that S stimulates Prl secretion by its possible direct action on the anterior pitui

ISSN:0028-3835    

DOI:10.1159/000122532

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Vasopressin was virtually absent from 5 microdissected hypothalamic areas and from the posterior pituitary glands of homozygous Brattleboro rats. The oxytocin concentration was normal in all these areas except for the arcuate nucleus, where it was absent. These results support the concept that Brattleboro rats have a specific defect in biosynthesis of vasopressin. The significance of the absence of oxytocin from the arcuate nucleus in these rats remains to be determined.

ISSN:0028-3835    

DOI:10.1159/000122533

出版商:S. Karger AG    

年代:1976

数据来源: Karger