ISSN:0028-3835    

DOI:10.1159/000124045

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The distribution of angiotensin II (AII)-immunoreactive cells and fibers was examined in adult male Sprague-Dawley rats with and without colchicine pretreatment. As seems to be the case for a number of other neuropeptides, AII is preferentially found in brain stem, hypothalamic, and limbic structures involved in the control of homeostatic functions. AII-stained cell bodies were most prominent in magnocellular parts of the paraventricular and supraoptic nuclei, and cells were also found in parvocellular parts of the former. Other hypothalamic nuclei containing cell bodies include the suprachiasmatic nucleus, the medial preoptic area, and perifornical parts of the lateral hypothalamic area. Of considerable interest was robust staining in several of the circumventricular organs, in particular the subfornical organ, where both cells and fibers were found. The results of water deprivation and nephrectomy suggest that this staining does not represent uptake of circulating peptide, but instead, represents AII-containing neural connections. In the thalamus, AII-stained cells were found in the paraventricular nucleus, the central medial nucleus, the nucleus reuniens, and rostral parts of the zona incerta. Two cell groups in the basal telencephalon, in the dorsal part of the bed nucleus of the stria teminalis and in the medial nucleus of the amygdala, lay at either end of an AII-stained pathway coursing through the stria terminalis. In the midbrain, immunoreactive cells were found in the interpeduncular and peripeduncular nuclei, and one pontine cell group was detected in the most lateral part of the lateral parabrachial nucleus. The only AII-stained cells in the medulla were in the nucleus of the solitary tract, near the margin of the area postrema. Fibers were found at all levels of the central nervous system, from the olfactory bulbs to the spinal cord, where terminal fields were observed in the substantia gelatinosa and in the intermediolateral cell column. Longitudinally oriented fibers were present throughout the periventricular fiber system and in the medial forebrain bundle, including its caudal extension in ventrolateral parts of the brain stem. It is suggested that, at many different levels, AIIserves as both a hormone and neurotransmitter for fluid balance.

ISSN:0028-3835    

DOI:10.1159/000124046

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Neurohypophyses from rats dehydrated and rehydrated for different periods of time have been analyzed by morphometry of electron micrographs and their oxytocin and vasopressin contents measured by radioimmunoassays. The time course of disappearance and reappearance of neurosecretory granules (NSG) parallels that of the hormone content of the neurohypophysis. Depletion of NSG during dehydration first occurs in the nerve endings and only later in the swellings. No change of the volumetric density of the microvesicles was detected but the time course of changes in the volumetric density of the endocytotic vacuoles varies according to the secretory state of the tissue. There was a significant increase in the volume of the gland 3 days after the beginning of the rehydration. This increase was associated with an increase in the volumetric density of the pituicytes. No change of the total number of endings, swellings and axons was observed. This demonstrates a hypertrophy of the pituicytes.

ISSN:0028-3835    

DOI:10.1159/000124047

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Thyrotropin-releasing hormone (TRH) stimulated in vivo growth hormone (GH) release in conscious and anesthetized young domestic fowl. The administration of the presumed metabolites of TRH, deamido-TRH (TRH-OH) and histidyl-proline diketopiperazine (HPD), was followed by small but significant (p < 0.05) increases in the plasma concentrations of GH in both conscious and anesthetized chicks. However, the ability of TRH-OH or HPD to stimulate GH secretion was less than that observed with a 100-fold lower dose of TRH. The administration of either TRH-OH or HPD with TRH increased the GH response over that observed with TRH alone. The ability of chicken plasma to degrade exogenous TRH in vitro was determined by measuring immunoreactive TRH (IR-TRH) content and by assessing the ability of the incubated samples to increase the plasma concentration of GH when administered to young fowl. The in vitro half-life of TRH was estimated to be 9.8 (by immunoassay) and 9.6 (by a biological index) min for plasma from adult male chickens and 23.9 (by immunoassay) and 20.2 (by biological index) min for plasma from 6-week-old chicks. This difference in degradation may account, at least in part, for the observed age-related decrease in the plasma concentration of GH in birds and for the diminished GH responsiveness of adult birds to exogenous TRH.

ISSN:0028-3835    

DOI:10.1159/000124048

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Studies were undertaken to determine the effects of chronic stimulation of opiate receptors on the negative feedback effects of testosterone (T) on luteinizing hormone (LH) secretion in the male rat. In an initial study, castrated male rats received replacement levels of T (2 ng/ml) or chronic morphine (M) treatment for 7 days. When initiated at the time of castration, both T and M treatments prevented the castration-induced hypersecretion of LH. However, when the treatments commenced 2 weeks after castration, only T restored LH secretion to the low levels seen in intact rats. In a second study, rats castrated 2 weeks previously were exposed to chronic M or placebo (control) treatment in the presence of various dosages of T. In rats receiving T alone, LH secretion was unaffected at T levels up to 600 pg/ml serum, but thereafter there was a dose-dependent suppression of LH release by T. Serum T levels which reduced LH secretion by 50 % were estimated to be 966 pg/ml. In contrast, in castrated rats receiving both M and T treatment, a 50% reduction in LH secretion was estimated to be at 300 pg T/ml serum and maximal inhibition of LH secretion was achieved at serum T levels of greater than 600 pg/ml. Neither T alone nor M plus T treatment altered the responsiveness of the anterior pituitary to LHRH in vitro. These findings indicate that M may enhance the sensitivity of the hypothalamus to T feedback by approximately 3-fold and raise the possibility of the existence of an opioid-sensitive neural component which may modulate the negative feedback effects of T on LH secretion.

ISSN:0028-3835    

DOI:10.1159/000124049

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The present studies were designed to answer three questions: (1) how will a progressive increase in serum estradiol (E2) in ovariectomized (OVX) rats affect progesterone (P4)-induced luteinizing hormone (LH) surge concentrations? (2) Can steroid-induced LH surges be correlated with estrogen nuclear receptor (E2Rn) and progestin cytosol receptor (PRc) levels in brain regions known to regulate LH secretion, and (3) do differences in pituitary responsiveness to LHRH in E2- or E2P4-treated OVX rats parallel changes in E2Rn and PRc concentrations in this gland? 1 week after ovariectomy of adult cyclic rats (day 0), Silastic E2 capsules were placed subcutaneously at 09.00 h and produced serum E2 levels of 6∼8 (low), 12–19 (medium) and 27–37 (high) pg/ml, respectively. 2 days later (day 2), some rats also received Silastic P4 capsules subcutaneously which elevated serum P4 concentrations to 10–12 ng/ml. In rats with low serum E2, P4 treatment induced peak serum LH levels of 913 ng/ml. When serum E2 was increased to the medium or relatively high physiologic range, P4 treatment resulted in LH surge levels of 4,686 and 5,030 ng/ml. OVX controls and E2-treated OVX rats were sacrificed at 10.00 h on day 2 and E2Rn and PRc were measured concurrently in the preoptic area (POA), mediobasal hypothalamus (MBH), corticomedial amygdala (CMA) and pituitary gland (PIT). Raising serum E2 from OVX levels to the low range significantly increased both E2Rn and PRc in MBH and PIT, but not in the POA or CMA. When serum E2 was raised from the low to medium range, E2Rn and PRc increased in MBH, PIT and POA, but only E2Rn levels were significantly elevated in CMA. Elevations in serum E2 from the medium to high range significantly increased E2Rn in POA and CMA, and PRc only in PIT. Pituitary responsiveness to LHRHon day 2 was evaluated in E2 and E2P4-treated rats. LHRH-induced LH release increased with increasing serum E2 concentrations. However, P4 treatment neither amplified nor suppressed LHRH-induced LH release in any of these E2-treated rats. We conclude from these studies that only E2-induced increases in POA and MBH PRc may be correlated with P4-amplification of LH

ISSN:0028-3835    

DOI:10.1159/000124050

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

In these studies we examined the temporal parameters of estradiol (E2) priming required before progesterone (P4) amplifies the surge release of luteinizing hormone (LH) in short-term ovariectomized (OVX) rats. Thereafter, we correlated the time of appearance and concentrations of estrogen nuclear (E2Rn) and progestin cytosol (PRc) receptors in brain regions known to be involved in the surge release of LHRH. Steroid receptor concentrations were also measured in the pituitary gland. 1 week after OVX (day 0), Silastic capsules containing E2 (150 µg/ml in oil s.c.) were placed at 09.00 h. The serum E2 concentrations produced by these capsules peaked (41 ± 2.1 pg/ml) at 10.00 h on day 0 and declined thereafter to values which ranged between 19 and 10 pg/ml on days 1 through 4. Some of these E2-treated rats also received 2 P4-containing Silastic capsules (50 mg/ml s.c. in oil) at 09.00 h on either days 0, 1, 2, 3 or 4. Serum P4 concentrations produced by such capsules were 9.3 ± 0.5 ng/ml. Blood was collected sequentially at 09.00 h and at hourly intervals from 12.00–18.00 h on the day that the animals received the P4 capsules and 10.00 and 15.00 h samples also were taken from each group the next day. LH surges occurred in these E2-treated rats in the afternoons of days 2–4, but not on days 0 and 1. P4 treatment on day 1 elicited an LH surge and on days 2–4 it amplified plasma LH surge concentrations and advanced by 1 h the time of release of this gonadotropin. Separate groups of OVX rats were sacrificed before and at various times after E2 treatment and the concentrations of E2Rn and PRc were measured concurrently in the preoptic area (POA), medial basal hypothalamus (MBH), corticomedial amygdala (CMA) and the pituitary glands (PIT) of these rats. The E2Rn levels in these tissues paralleled the changes which occurred in serum E2. 1 hour after placing the E2 capsules (10.00 h day 0), E2Rn levels increased significantly compared to OVX controls, and thereafter they had stabilized by 15.00 h on day 1 and remained constant through 15.00 h on day 4. There was no E2 induction of PRc within 6 h after E2 treatment (10.00 and 15.00 h on day 0) in POA, MBH or PIT. Further, regardless of the duration of treatment, E2 did not induce PRc in the CMA. The first significant induction of PRc that we observed was at 15.00 h on day 1 (30 h after E2) and it then remained constant thereafter through 15.00 h on day 4 in POA, MBH and PIT. Pituitary responsiveness to 2 pulse injections of LHRH increased with the duration of E2 exposure, but additional P4 treatment did not further amplify LHRH-induced LH release on any of the days examined. Consequently, it requires 24 h of E2 priming for P4 treatment to amplify LH surges in short term OVX rats and this physiological effect of P4 directly correlates with the first significant E2 induction of PRc in POA, MBH and PIT (day 1). The data further emphasize that amplification of LH surges in E2-treated rats is not due to an increase in responsiveness of the pituitary gland to LHRH but rather, such P4 effects are mediated via brain mechanisms involved in the surge release

ISSN:0028-3835    

DOI:10.1159/000124051

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

To study the secretory pattern of growth hormone (GH) in the adult male rat in a continuous sleep state, the GH concentration was measured in blood sampled at 10-min intervals through an intracardiac cannula for 9–10 h long-term anesthesia with thiopental sodium. The cortical EEG was monitored to maintain stable EEG sleep throughout the sampling period. In 41 animals subjectd to anesthesia, 32 showed an apparent fluctuation in GH levels. The analysis of the time series of the GH concentration in blood by the power spectrum and least-squares method revealed that 27 animals had periodicities within the mean ± 2SD range obtained for the unanesthetized, but similarly sampled, animals from 2.40 to 3.85 h. The mean (± SE) of the periodicities for 27 animals was 3.01 ± 0.06 h, similar to that obtained for the unanesthetized animals, approximately 3.0 h. The results indicate that, although the GH-controlling mechanism in the rat is facilitated under sleep, it has a 3.0-hour period ultradian rhythm mechanism that is indepedent from that for s

ISSN:0028-3835    

DOI:10.1159/000124052

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Immobilization of adult male rats resulted in concomitant, significant releases of prolactin (PRL) and oxytocin (OT). Naloxone (0.2 mg/kg, i.p.) administration 30 min prior to initiation of restraint resulted in a significant diminution of the PRL response to stress. On the other hand, a significant augmentation of OT release was observed. These results demonstrate that concomitant releases of OT and PRL in response to a given physiologic stimulus (stress) can be dissociated and suggest that the hypothalamic events which are responsible for the release of these hormones during stress are different.

ISSN:0028-3835    

DOI:10.1159/000124053

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

The β-adrenergic agonist 1-isoproterenol (ISO) (10–9–10–7M) provoked a prompt and profound increase of intracellular c-AMP accumulation in monolayer cultures of rat anterior pituitary. In superfused reaggregate cell cultures ISO also stimulated c-AMP outflow. The effect was blocked by propranolol and the highly selective β2-receptor blocker ICI 118.551. Epinephrine (E), norepinephrine (NE) and the highly selective β2-agonist zinterol (ZIN) also stimulated c-AMP accumulation. The order of potency ZIN ≧ E NE together with the high potency of ICI 118.551 suggests the β-effect is mainly through the β2-receptor subtype. The same concentrations of ISO strongly stimulated growth hormone (GH) release and, as previously shown, prolactin (PRL) release from superfused reaggregate cell cultures, but not luteinizing hormone or thyroid stimulating hormone release. Stimulation of PRL and GH release from these cultures was also induced by the adenylyl cyclase activator forskolin. Since interference of β-adrenergic effects on contaminating fibro-blasts or endothelial cells could be reasonably excluded, the present data suggest that β-adrenergic stimulation of c-AMP accumulation in anterior pituitary cells elicits GH a

ISSN:0028-3835    

DOI:10.1159/000124054

出版商:S. Karger AG    

年代:1985

数据来源: Karger