摘要:

In order to characterize the receptors which mediate the adrenocorticotropic hormone (ACTH) response to vasopressin in conscious animals, plasma 11-hydroxycorticosteroid concentration was measured in conscious dogs during the infusion of vasopressin or structural analogs of vasopressin which exhibit selective antidiuretic or vasoconstrictor activity. Vasopressin (1.0 ng/kg/min for 60 min) increased mean arterial pressure, decreased heart rate and increased plasma corticosteroid concentration from 1.0 ± 0.2 to 2.2 ± 0.2 µg/dl (p < 0.001). A specific antagonist of the vasoconstrictor activity of vasopressin, d(CH2)5MeTyrAVP (10 µg/kg), completely blocked the cardiovascular and corticosteroid responses to vasopressin. A selective vasoconstrictor (V1) agonist, PheOrnOT (1.0 ng/kg/min), which produced the same cardiovascular responses as vasopressin, increased plasma corticosteroid concentration from 1.1+0.1 to 2.9 ±0.9 µg/dl (p < 0.005). In marked contrast, a selective antidiuretic (V1) agonist, dDAVP (1.0 ng/kg/min) had no effect on blood pressure, heart rate or plasma corticosteroid concentration. These results indicate that the stimulation of ACTH release by vasopressin in conscious dogs is mediated by receptors which resemble vasoconstrictor-type (V1) receptors rather than antidiuretic-type (V<) rece

ISSN:0028-3835    

DOI:10.1159/000124256

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The role of the brain renin-angiotensin system in the ACTH response to ether stress in rats was investigated by injecting the angiotensin II receptor blocking drug saralasin, the angiotensin II converting enzyme inhibitors enalaprilat and captopril, and the renin inhibitor L 363714 intraventricularly and measuring the ACTH and corticosterone concentration in plasma 10 min after ether stress. ACTH and corticosterone were elevated to at least the same level in rats treated with the inhibitors as they were in rats treated with the corresponding vehicles; indeed, ACTH values were somewhat greater in stressed rats treated with the converting enzyme inhibitors and the renin inhibitor. ACTH values in the absence of ether were not affected by saralasin, enalaprilat, and captopril and were increased by L 363714. The data do not support the hypothesis that the brain renin-angiotensin system is involved in the maintenance of ACTH secretion or that it mediates the increase produced by ether stress.

ISSN:0028-3835    

DOI:10.1159/000124257

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

In the present investigation CNS epinephrine (EPI) biosynthesis was selectively interrupted with specific norepinephrine N-methyltransferase (NMT) inhibitors, SK&F 64139 (Smith, Kline & French Laboratories) and LY 78335 (Eli Lilly & Co. Research Laboratories), to determine the effects of central EPI depletion on basal and cold, thyrotropin-releasing hormone, and hypothalamic somatostatin antiserum induced thyrotropin (TSH) secretion in chronically cannulated rats. Because these NMT inhibitors also are α2-adrenergic receptor blockers, the effects of α2- and α1-adrenergic blockade and α2-activation on plasma TSH were assessed with rauwolscine and corynanthine and B-HT933, respectively. Serum T4 and plasma corticosterone were also measured. Blockade of CNS EPI synthesis resulted in inhibition of basal and cold and thyrotropin-releasing hormone induced TSH release, suppression of serum T4, and increased corticosterone release. The stimulatory effect of SRIF antiserum on plasma TSH was not altered by SK&F 64139. α2-adrenergic blockade suppressed plasma TSH levels, but not to the same degree as the NMT inhibitors; activation of α2-receptors enhanced TSH secretion. Thus, it is possible that part of the effect of the NMT inhibitors on TSH was due to α2-blockade. α1-adrenergic blockade also lowered plasma TSH. These results indicate that (1) central EPI systems have a stimulatory role in TSH regulation, possibly mediated by α2-adrenergic receptors, (2) cold-induced TSH release is mediated, in part, by EPI, and (3) central EPI systems exert an inhibitory effect on the hypothalamic-pituitary-adre

ISSN:0028-3835    

DOI:10.1159/000124258

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The characteristic electrophysiological manifestations of LHRH ‘pulse generator’ activity were unaffected by prolonged elevations in plasma LH concentrations achieved by the administration of a long-acting LHRH agonist. These findings do not lend support to the existence of a ‘short-loop feedback’ inhibition of LHRH ‘pulse generator’ act

ISSN:0028-3835    

DOI:10.1159/000124259

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Intact pubertal or young adult male rats release more luteinizing hormone in response to luteinizing hormone releasing hormone (LHRH) if pretreated with LHRH than if pretreated with saline. Castrated male rats do not show this self-priming effect of LHRH. In an attempt to determine the testicular factor responsible for the maintenance of the self-priming effect, pubertal male rats were castrated and implanted subcutaneously with various sizes of testosterone-filled Silastic capsules. Control rats were castrated or sham-operated and implanted with empty capsules. Rats were examined for a self-priming effect 4 days later. All sizes of testosterone capsules used maintained the self-priming effect. Three additional experiments were performed to determine the ability of dihydrotestosterone, estradiol and androstenedione to maintain a self-priming effect. The following groups were included in each experiment: castrated plus empty capsule, castrated plus testosterone-filled capsule, castrated plus one of two sizes of capsule filled with the steroid of interest, and sham-operated plus empty capsule. Dihydrotestosterone and estradiol, but not androstenedione were capable of maintaining a self-priming effect. Since it is generally considered that dihydrotestosterone cannot be aromatized to estrogen, this action of estradiol and dihydrotestosterone is probably accomplished by different mechanisms.

ISSN:0028-3835    

DOI:10.1159/000124260

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The distribution of arginine vasotocin immunoreactivity (irAVT) was investigated in the brain of male rough-skinned newts (Amphibia: Taricha granulosa)using microdissection and radioimmunoassay techniques. The highest levels of irAVT were observed in the neuroendocrine hypothalamo-hypophysial system. However, detectable quantities of irAVT (greater than 0.40 ng/mg protein) also were observed in extrahypothalamic areas such as pallium, amygdala, striatum and thalamic, tectal and brainstem nuclei. No irAVT was detected in the olfactory bulb, rostral telencephalon, or in specific areas of the caudal telencephalon and diencephalon. These results indicate that, in amphibians, AVT is distributed among a wide range of brain areas and that there is regional specificity in irAVT concentrations.

ISSN:0028-3835    

DOI:10.1159/000124261

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

A single injection of 25 µg melatonin was given subcutaneously in 0.1 ml saline either at 3 h into the light phase (morning) in female Syrian hamsters or at 1 h before the beginning of the dark phase (evening) in males (L/D 14/10 h). In both cases, the maximal mean serum values seen at 20 min after injection (50 ng/ml) were more than 1,000 times the normal nocturnal melatonin concentration. By 1 h after injection, serum melatonin had fallen to 10% (morning) or 4% (evening) of the respective 20-min value. The average half-times for plasma concentration during the second hour after injection were 14 min in the morning and 13 min in the evening. After either morning or evening injection, serum melatonin reached normal daytime concentration between 2 and 4 h after injection

ISSN:0028-3835    

DOI:10.1159/000124262

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The release of luteinizing hormone (LH) in response to electrical stimulation of limbic centres, namely the medial preoptic region (MPO) medial basal hypothalamus (MBH) and the medial amygdala (AME) has been studied in the anaesthetised gonadectomized cat. Chronically gonadectomized cats were anaesthetised with pentobarbitone or Althesin and paired bipolar stimulating electrodes were aimed at the MPO, AME or MBH. The effect of electrical stimulation of these regions on the secretion of LH was studied by radio-immunoassay of LH in serial blood samples taken before, during and after stimulation. No change in plasma LH in response to electrical stimulation was ever recorded during pentobarbitone anaesthesia. During Althesin anaesthesia stimulation in the MPO more often than not resulted in a peak of LH release during stimulation. A peak release of LH during stimulation was also recorded when electrodes were placed in the arcuate-median eminence region of the MBH. The time-course of these peaks in LH secretion was similar to the time-course of the plasma LH responses recorded following a single intravenous injection of gonadotrophin-releasing hormone (GnRH). In contrast, electrodes placed in AME had no effect on plasma LH during electrical stimulation, but immediately after stopping it, a small LH peak was recorded. The time-course of these responses suggests a pulse release of GnRH, the rapid response to MPO and MBH stimulation possibly being the result of a direct action on GnRH neurons while the delayed AME response may be produced by AME projections to the GnRH release system. These responses could be likened to the surge of LH which in the cat occurs post-coitus.

ISSN:0028-3835    

DOI:10.1159/000124263

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

In 8-day-old rat newborns, the pituitary response to 2 min of ether inhalation was noted to vary according to sex. Plasma ACTH levels were similarly increased in males and females at the end of ether exposure; however, during the following 30 min, ACTH levels were always higher in females than in males. In order to verify that the putative masculinization of some neuroendocrine pathways involved in the pituitary response to ether stress was the result of the transitory surge of testosterone at birth, fetuses at term were delivered by cesarean section and thereafter immediately castrated or sham-castrated under cold anesthesia (males), injected with testosterone heptylate (1 mg s.c.) or olive oil used as solvent (females) before being put in the care of a nurse. The rise in plasma testosterone levels during the 1st h after birth was prevented or stopped in males put at 2 °C. At the 8th postnatal day, the newborns were subjected to 2 min of ether inhalation; they were sacrificed either just, before or after the end (0 and 30 min) of the stress procedure. Plasma immunoreactive ACTH level and adrenal corticosterone content were measured. The pituitary response, shown by the ACTH increase, in castrated or sham-castrated males and testosterone-injected females was similar to that of intact males but very different from that observed in olive-oil-injected or intact females. The rise in adrenal corticosterone content 30 min after ether inhalation was greater in intact and olive-oil-injected females than in testosterone-injected ones or in males; adrenal response was well correlated with the maintenance of ACTH release in the former and the decrease following transitory surge in the latter. Present data suggest – in the male, prenatal differentiation of the neuroendocrine pathways involved in the pattern of ACTH release in response to ether inhalation – in the female, the existence of androgen-sensitive structures in early postnatal

ISSN:0028-3835    

DOI:10.1159/000124264

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Brains from 4 normal and 4 colchicine-treated rats were studied for the presence of growth hormone-releasing factor (GRF) using an antibody directed against rat hypothalamic GRF (rGRF). Noncolchicine-treated animals showed intense staining in the external layer of the median eminence. Rats pretreated with intraventricular colchicine for 48 h showed localization of GRF-containing cell bodies in the arcuate nucleus, the perifornical area, the lateral basal hypothalamic region and lateral to the ventromedial nucleus and the premammillary nucleus. This pattern of distribution is consistent with the postulated role of GRF in hypothalamic regulation of growth hormone secretion. Our results confirm the predominant localization of GRF perikarya in the arcuate nucleus of the rat which has been noted in studies using antibodies directed against both human pancreas GRF (hpGRF) and rGRF, and demonstrate a unique pattern of rGRF-positive cell bodies elsewhere in the hypothalamus. No rGRF perikarya or processes were seen outside the hypothalamus.

ISSN:0028-3835    

DOI:10.1159/000124265

出版商:S. Karger AG    

年代:1986

数据来源: Karger