摘要:

To address the issue of whether, after morphine treatment, the reduced release of dopamine (DA) into portal blood is entirely responsible for the increased prolactin (PRL) release, the following study was conducted. The concentration of DA in plasma from a single portal vessel of untreated, ovariectomized rats was 1.85 ± 0.33 ng/ml (mean ± SE). Treatment of ovariectomized rats with α-methyl-p-tyrosine (αMT) caused a 91% reduction in the concentration of DA in portal plasma. Infusion of DA (0.4 µg/min/kg BW) into a jugular vein of rats pretreated with αMT restored the DA concentration in portal plasma to that seen in untreated rats. Injection of morphine sulfate elicited a marked increase in the concentration of PRL in plasma. Infusion of DA at rates of 0.4 and 0.8 µg/min/kg BW suppressed by 52 and 75%, respectively, the secretion of PRL after morphine treatment. Infusion of DA had no effect on the release of PRL induced by intra-cerebroventricularly administered β-endorphin. Although treatment of rats with αMT caused release of PRL that was similar to that seen in rats treated with morphine, infusions of DA at 0.4 and 0.8 µg/min/kg BW into αMT-treated, ovariectomized rats suppressed the secretion of PRL by 89 and 96%, respectively. Thus, after morphine treatment, the decreased release of DA into portal blood is not in itself sufficient to account for the increase seen in the secretion of PRL. It is suggested that morphine and opiate-like peptides induce the release of a hypothalamic substance(s) that stimulates P

ISSN:0028-3835    

DOI:10.1159/000123867

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

When administered during the critical perinatal period, estrogen permanently modifies both male and female reproductive function. This study evaluated the influence of exogenous estrogen administered during this time on the hypothalamic LHRH content and on gonadotropin secretion in adult male and female rats. LHRH content in the preoptic-anterior hypothalamic (PO/AH) and midhypothalamic (MH) areas of neonatally estrogenized rats (1 mg on postpartum day 2) and of control male and female rats during the estrous cycle was determined by radioimmunoassay between 80 and 90 days of age. LHRH content was significantly greater in the PO/AH of neonatally estrogenized females than in estrogenized males whereas no differences in LHRH content of the PO/AH existed between control male and female rats. Neonatal administration of estrogen resulted in increased LHRH content in the MH of female rats and decreased LHRH content in male rats, as in the PO/AH; however, these differences were less marked in the MH and not statistically significant. The marked increase in serum LH concentration present in control cycling females in proestrus was abolished by neonatal estrogen treatment. Exposure to neonatal estrogen reduced FSH concentrations in males. The data are consistent with the concept that the hypothalamic-pituitary system is modified by estrogen circulating during the period of sexual differentiation. LHRH synthesis and release appear to be directly modified by neonatal estrogen. The effects of neonatal estrogen treatment in the PO/AH and MH areas may possibly involve two disparate types of alterations of developing LHRH neurons which modulate gonadotropin secretion in the adult rat.

ISSN:0028-3835    

DOI:10.1159/000123868

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Anatomical studies have suggested that the posterior pituitary peptide, vasopressin (VP, antidiuretic hormone) may be released at central neural sites other than the neurohypophysis. Immunohistochemical techniques allow VP to be visualized at numerous sites in the central nervous system (CNS). VP can also be measured in cerebrospinal fluid (CSF). Some of the stimuli which evoke VP release from the posterior pituitary may also elevate CSF VP levels. VP may play an important part in a variety of CNS functions. Substantial evidence exists implicating VP in learning and memory processes. VP may have a role in cardiovascular regulation through central pathways. Further, VP appears to act on the regulation of body temperature during fever. Other areas of central regulation where VP may be important include circadian rhythmicity, control of water intake, control of permeability of brain capillaries to water, central regulation of ACTH release and nociception. It appears that at least some of these central effects of VP involve an interaction with catecholaminergic neurotransmission.

ISSN:0028-3835    

DOI:10.1159/000123869

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Synthetic ovine corticotropin-releasing factor (0.1–1.0 µg) was injected intravenously to 6 chronically cannulated ovine fetuses between 104 and 149 days of gestation (term 142–152 days). Arterial plasma immunoreactive adrenocorticotropin was first elevated by this procedure if the fetuses were between 118 and 130 days of gestation, and an increased response occurred later in gestation. This suggests that a progressive reset of the hypothalamic-pituitary-adrenal feedback relationship occurs over the last 2–3 weeks of gestation in the ovine

ISSN:0028-3835    

DOI:10.1159/000123870

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Somatostatin-28(1-12)-like immunoreactivity was measured in extracts of rat hypophysial portal blood and peripherial blood. The concentration of somatostatin-28(1–12) was higher in portal than in peripheral extracts, and its release into portal vessel blood was increased 4- to 5-fold by electrical stimulation of the median eminence. These results show that somatostatin-28(1–12) may be a physiological neurohormone and/or neurotransmit

ISSN:0028-3835    

DOI:10.1159/000123871

出版商:S. Karger AG    

年代:1984

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000123872

出版商:S. Karger AG    

年代:1984

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000123873

出版商:S. Karger AG    

年代:1984

数据来源: Karger