摘要:

Autoradiographic methods were used to study the location of estrogen-concentrating cells in the brain of the female hamster. In the hypothalamus, well-labelled cells were reliably found in the posterior medial preoptic area (MPOA), the anterior hypothalamus (AHA), and the ventromedial (VM), arcuate (ARC) and ventral premammillary nuclei (VPM). In the limbic system, well-labelled cells were found in the ventro-lateral septum, bed nucleus of the stria terminalis, and the medial and cortical nuclei of the amygdala. Labelled cells, in small numbers, were also detected in the mesencephalic central gray (CG), lateral hypothalamus, subiculum and entorhinal cortex. The neuro-anatomical pattern of estrogen-concentrating cells in the hamster supports the concept of a generalized vertebrate pattern. Furthermore, a comparison of hamster and rat patterns of cellular 3H-estradiol (3H-E2) concentration appears to suggest that species differences in their responsiveness to estrogen may be paralleled by differences in estrogen binding.

ISSN:0028-3835    

DOI:10.1159/000122626

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The effects of prolactin (PRL) administration on catecholamine turnover in various brain regions of ovariectomized rats were determined by observing the decline of dopamine and norepinephrine concentrations after α-methyltyrosine (αMT) administration. PRL had no effect on the steady state concentration of dopamine in the median eminence, anterior hypothalamus and corpus striatum or on the norepinephrine concentration in the anterior hypothalamus. However, PRL selectively enhanced dopamine turnover in the median eminence and anterior hypothalamus after a latent period of 10–26 h. In addition, PRL administration significantly decreased serum concentrations of LH and FSH. These results suggest that the PRL-induced increase in activity of dopaminergic neurons in the median eminence or anterior hypothalamus may be responsible for the reduction of the post-castration rise in serum concentrations of LH and

ISSN:0028-3835    

DOI:10.1159/000122627

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Weanling rats received bilateral electrolytic lesions in the dorsomedial (DMH) or ventromedial (VMH) hypothalamic areas destroying primarily the dorsomedial (DMN) or ventromedial (VMN) hypothalamic nuclei. Sham-operated rats served as controls. Lesions in the VMN and DMN, both of which have previously been shown to disrupt normal diurnal feeding rhythms, were also observed to disrupt normal plasma corticosterone rhythms in the present study. The a.m. values of plasma corticosterone in the DMN-lesioned rats were higher than the sham-operated controls. In the p.m., the values of both VMN- and DMN-lesioned rats were lower than those of the controls but unchanged in comparison to their own a.m. concentrations. This disruption of the normal diurnal plasma corticosterone rhythm persisted for at least 9 post-operative weeks.

ISSN:0028-3835    

DOI:10.1159/000122628

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

In sexually immature female rats ‘primed’ with a unilateral basal hypothalamic lesion on day 23 of life, a gonadotropin surge was triggered by progesterone (P) on day 26. The influence of sequential ovariectomy (OVX) on this response was studied in an attempt to elucidate the mode of action of brain lesions inducing precocious sexual maturation in this species. OVX, carried out on days 23–26, abolished or greatly reduced the LH surge, but had little effect on basal LH concentrations. In contrast, basal FSH concentrations rose rapidly after OVX. In lesioned rats, the post-castration rise of FSH could be prevented by leaving the ovaries in place during the 1st 24 or 48 h. It is concluded that the lesion-induced maturation of the positive feedback mechanism underlying the pubertal preovulatory gonadotropin surge is mediated by the ovaries. In prepubertal rats at this age, tonic FSH release, but not tonic LH release, is under tight negative feedback co

ISSN:0028-3835    

DOI:10.1159/000122629

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Rats exposed to continuous light show no significant differences in serotonin (5-HT) uptake by the suprachiasmatic nuclear region (SNR) at 10.00 and 22.00 L, while in continuous darkness, the uptake at 10.00 D is significantly higher than uptake at 22.00 D. In consideration of the role of the suprachiasmatic nucleus in light-mediated control of neuroendocrine activity, this suggests endogenous generation or control of this uptake rhythm. An effect of sham-pinealectomy in decreasing 5-HT uptake was found, but cannot be fully interpreted at this time. The lack of effect of castration or adrenalectomy suggests that these endocrines have little if any direct effect on 5-HT mechanisms in the SNR.

ISSN:0028-3835    

DOI:10.1159/000122630

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The involvement of adrenergic, serotonergic and cholinergic mechanisms in the diurnal surge of plasma prolactin (Prl) secretion has been examined using ovariectomized, polyestradiol phosphate-treated (PEP) rats bearing aortic catheters. An afternoon surge in plasma Prl was observed to peak at 15.00 h and 17.00 h followed by declining levels at 19.00 and 21.00 h. This pattern was observed between 5 and 21 days after PEP administration. The α-adrenergic blocker, phenoxybenzamine (Phenox), completely prevented the Prl surge. The β-blocker, propranolol (Propra), appeared to delay the onset and intensity of the diurnal Prl surge so that maximum levels were observed at 19.00 and 21.00 h. The serotonergic blocker, methysergide (MES), delayed the maximum diurnal Prl level until 21.00 h, while cyproheptadine (Cypro), another serotonergic blocker, significantly inhibited the surge. The muscarinic cholinergic agonist, arecoline (Arec), when administered at 12.00 h, delayed the surge, while the repeated administration of Arec completely blocked the surge. Atropine (Atro) (10 m/kg at 12.00 h and 5 mg/kg every 2 h thereafter) did not have any effect on the Prl surge, but when administered simultaneously with Arec, prevented the inhibitory effect of Arec on Prl release. The data suggested that the adrenergic and serotonergic systems have a positive input in the occurrence and magnitude of the surge and that the cholinergic system does not appear to have a physiologic role in tonically inhibiting Prl release, but may function under certain special condition

ISSN:0028-3835    

DOI:10.1159/000122631

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Electrolytic lesions were made in the lateral (LTN), medial (MTN) or in both terminal nuclei of the accessory optic tract in female ferrets. Either the ipsilateral or contralateral eye was removed. Complete destruction of both nuclei, as assessed by both histological and autoradiographic criteria, did not prevent the acceleration of estrus by artificial long days (L: D, 14:10) in any animal. Although the ferret has no anterior (inferior) accessory tract, lesions were also made in the medial forebrain bundle (MFB) area in ipsilaterally and contralaterally enucleated animals. Estrus still occurred in response to artificial long days in these animals. These experiments suggest that the accessory optic system in the ferret does not transmit information to the pineal regulating the annual breeding season.

ISSN:0028-3835    

DOI:10.1159/000122632

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Nuclear or total tissue binding of 3H-estradiol (3H-E2) was measured 1 h after i.v. injection in adult male and female rats gonadectomized 2 days, 1 week or 3 months earlier. Diethylstilbestrol- (DES) blockable nuclear 3H-E2 binding was highest in the anterior pituitary (PIT), followed by the preoptic area-anterior hypothalamus (POA-AH) and median eminence-basal hypothalamus (ME-BH), the amygdala (AMYG), dorsal hypothalamus (DH) and prehypothalamic area (PHA) and cerebral cortex (CX). DES administration reduced total tissue 3H-E2 uptake in the uterus of all groups, in the neurohypophysis (NH) of most groups and in the pineal of animals gonadectomized for 3 months. In both males and females, nuclear uptake of 3H-E2 was about 1.4 times higher 3 months after gonadectomy than 2 days after gonadectomy in the PIT and all brain areas except the ME-BH, where binding had approximately doubled during the same time period. Total 3H-E2 binding per organ in the NH was higher 3 months than 1 week or 2 days after gonadectomy in females. Nuclear 3H-E2 binding in the PIT was higher in males than in females 1 week after gonadectomy. There were no other sex differences in nuclear or total tissue 3H-E2 binding. The results suggest that the decrease in estradiol (E2) sensitivity of neuroendocrine mechanisms involved in gonadotropin secretion and reproductive behavior following prolonged absence of the gonads is not due to a decline in the ability of the PIT and several brain areas to bind E2, as measured 1 h after 3H-E2 injection.

ISSN:0028-3835    

DOI:10.1159/000122633

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Inhibitors of dopaminergic neurotransmission, such as reserpine (RES), given alone or combined with α-methyl-p-tyrosine (α-MpT) or Ro 4-4602, as well as haloperidol (HAL) and sulpiride (SUL), induced highly elevated serum prolactin (Prl) concentrations in intact rats. In contrast, the dopaminergic agonists apomorphine (APO), lisuride hydrogen maleate (LHM), D-amphetamine (AMPH), piribedil and L-dopa greatly lowered the high serum Prl concentrations in female rats induced by i.p. pretreatment with 2 mg/kg RES. Additional inhibition of catecholamine synthesis in RES-treated animals by α-MpT abolished the effect of AMPH, which indicates that the effect of this compound is mediated through newly synthesized dopamine (DA), while the effect of APO and LHM remained unchanged. Inhibition of dopa decarboxylation by Ro 4–4602 within the whole body abolished the effect of L-dopa, while lower dosages of Ro 4–4602, which do not penetrate the blood-brain barrier, had less effect. The noradrenergic receptor-stimulating agent clonidine (CLON) had no Prl-lowering effect in RES-treated female rats. In hypophysectomized rats bearing 4 pituitaries transplanted under the kidney capsule, APO and LSM still lowered serum Prl concentrations, while AMPH had no effect; SUL produced a strong increase. These results support the hypothesis that DA has a dominant role as an inhibitor of Prl secretion by acting itself as the Prl inhibiting factor (PIF) on dopaminergic receptors located within the pit

ISSN:0028-3835    

DOI:10.1159/000122634

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122635

出版商:S. Karger AG    

年代:1976

数据来源: Karger