摘要:

The ACTH-releasing activites of angiotensin I, angiotensin III, [des (Asp1, Arg2)]Ang II, and [des (Asp1, Arg2, VaP3 [des (Asp1, Arg2)]Ang II. [Des (Asp1, Arg2, Val3)]Ang II was nonstimulatory. Angiotensin I-induced ACTH was completely inhibited by the addition of converting enzyme inhibitor SQ2O885. A similar dose-related inhibition of Ang II-stimulated ACTH release by [Sar1, Ala9]Ang II and [Sar1, Gly8]Ang II was demonstrated. Corticosterone (5 nM) decreased Ang II (10 nM) mediated ACTH release to control values while dibenzyline (10 μM), an alpha-adrenergic antagonist and cyproheptadine (10 μM), a serotonin antagonist did not alter the stimulation of ACTH by Ang II. This study suggests (1) the N-terminal amino acids of Ang II are important for the ACTH stimulatory action of Ang II, (2) [Sar1, Ala8]Ang II and [Sar1, Gly8]Ang II are specific Ang II antagonists at the pituitary level towards the ACTH releasing effect of Ang II, and (3) corticosterone inhibits the in vitro pituitary ACTH release by Ang II while dibenzyline and cyproheptadine have no effec

ISSN:0028-3835    

DOI:10.1159/000123463

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

We have recently reported that luteinizing hormone (LH) is present in the hypothalamus of rats. It has chromatographic and biologic characteristics similar to pituitary LH. In this report we focus on extrahypothalamic LH that is widely distributed in the rodent central nervous system. This material has a chromatographic profile similar to that of pituitary LH. Serial dilution of this material is parallel with dilutions of rat pituitary LH in the immunoassay. Brain extracts are active in the testis LH radioligand receptor assay and in the rat interstitial cell testosterone secretion bioassay. Prior incubation of extract with LH antibody significantly attenuates both of these activities. Thus, extrahypothalamic LH has immunologic, chromatographic, and biologic characteristics similar to hypothalamic and pituitary LH.

ISSN:0028-3835    

DOI:10.1159/000123464

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

To examine the influence that the vagus nerve may have on ovarian development and on the timing of puberty, both anterior and posterior vagi were sectioned at the abdominal level in 24-day-old female rats. Abdominal vagotomy (AV) resulted in a marked delay in the onset of puberty, as measured by the age at vaginal opening and at first diestrus. No differences in circulating levels of LH, FSH, PRL, TSH or GH between control and vagotomized rats were observed between the time of AV and vaginal opening. Nevertheless, estradiol (E2) and progesterone (P) response to human chorionic gonadotropin (hCG) in vitro was profoundly depressed in ovaries of vagotomized rats. This decreased ovarian secretory activity was further reflected in vivo by a reduced ovarian weight and, more prominently, by a reduced uterine weight. Ovarian release of androgens, however, was increased in vagotomized rats suggesting an enhanced activity of the thecal-interstitial gland compartment of the ovary. The reduced E2 and P response to hCG could not be attributed to changes in hCG-LH or FSH receptor number. Likewise, the inhibitory effect of AV on the ovary was not due to changes in ovarian β-adrenergic receptor content. Concentration of LHRH binding sites in granulosa cells was increased after AV. However, since LHRH receptor content decreases with ovarian maturation, this change may simply reflect delayed ovarian development rather than being the actual factor mediating the effect of AV. The delay in puberty induced by AV was not due to interference with nutrition of the animal, because at no age examined was the body weight of vagotomized rats different from that of controls. In addition, the effect of AV was not due to a decreased availability of cholesterol to the ovary, because levels of high- and low-density lipoproteins were normal in vagotomized rats. It is concluded that AV delays the onset of puberty and depresses ovarian function by mechanisms which do not involve alterations in ovarian gonadotropin or β-adrenergic receptors, changes in serum levels of pituitary hormones or availability of precursors for steroid synthesis. The possibility arises that the vagal control of the ovary is, instead, exerted by peptidergic fibers known to be contained in the abdominal vagu

ISSN:0028-3835    

DOI:10.1159/000123465

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The effect of N-acetylserotonin (NAS) on serum levels of thyroid-stimulating hormone (TSH) in the male rat was investigated. In the first experiment, NAS and carrier were injected intraperitoneally into rats. The animals were sacrificed 30 and 60 min after injection. It was found that NAS (100 μg/rat) significantly depressed serum TSH 60 min after injection when compared with saline-injected controls. In another experiment in which samples were obtained from rats at 0, 30, 60, 90 and 120 min after injection, significant decrease in serum TSH was observed at all time intervals after NAS (100 μg/rat) injection while no such difference was observed in the saline-injected group. It is suggested that NAS may exert an inhibitory effect on TSH secretio

ISSN:0028-3835    

DOI:10.1159/000123466

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Reversed-phase, high-performance liquid chromatography (HPLC) was carried out to characterize rat hypothalamic corticotropin-releasing factor (CRF) using synthetic ovine CRF as a marker. Samples were injected onto a stainless steel column (4 × 250 mm) packed with Hitachi gel 3053. The column was eluted using a gradient elution of increasing acetonitrile concentration, in a mixture of NaCl-HCl at a flow rate of 1.0 ml/min, monitoring the column effluent at 220 nm with an UV detector. Fractions eluted every 1–2 min were collected and lyophilized for subsequent CRF bioassay and radioimmunoassay. When various neuropeptide mixtures including synthetic ovine CRF were injected onto the column, synthetic ovine CRF was well separated from the other neuropeptides with a gradient of 0–60% acetonitrile in 0.1 M NaCl-0.01 N HCl or 0–80% acetonitrile in 0.05 M NaCl-0.01 N HCl. The median eminence extracts showed two main peaks of CRF bioactivity on HPLC. One (small CRF) coeluted with arginine vasopressin and oxytocin markers, and the other (big CRF) appeared near the position of synthetic CRF and was divided into two peaks. One coeluted with synthetic ovine CRF and the second eluted after synthetic CRF, showing high CRF activity. Three or four peaks of CRF immunoreactivity appeared on HPLC and the main peak appeared after synthetic ovine CRF marker. Our results suggest that rat CRF is different from ovine CRF, and the total lipophilicity of amino acid residues of rat CRF may be higher than that of ovi

ISSN:0028-3835    

DOI:10.1159/000123467

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Male ferrets born in the laboratory received subcutaneous Silastic capsules containing either the aromatase inhibitor, androst-1,4,6-triene-3, 17-dione (ATD), the 5 α-reductase inhibitor, testosterone-17β-carboxylic acid (17βC), or no hormone, for 15 days beginning on the day of birth; an additional group of females received empty Silastic capsules. All ferrets were gonadectomized when 11 weeks of age and were subsequently tested for masculine sexual behavior after a latin-square sequence of treatments with subcutaneous Silastic capsules containing testosterone (T), estradiol (E), or dihydrotestosterone (DHT). After T, control males displayed significantly more neck gripping, mounting and pelvic thrusting than control females, and males treated neonatally with ATD or 17βC were no less responsive than control males. After DHT, little masculine sexual behavior was shown by any group. After E, the duration of mounting was significantly longer in control and ATDmales than in control females or 17βCmales. Subsequently, however, there were no differences between control and 17βCmales on any parameter of masculine sexual performance, when they were retested sequentially after subcutaneous implantation of E followed by E + DHT. Additional groups of newborn male and female ferrets received subcutaneous capsules containing either ATD, 17βC, or no hormone and were killed on postnatal day 7. Administration of ATD, but not 17βC, strongly inhibited aromatase activity in the hypothalamus + preoptic area. In all groups, the formation of DHT from T was very low in both H + POA and cerebral cortex; however, neonatal administration of 17βC, but not ATD, significantly inhibited cortical 5α-reductase activity. Plasma concentrations of T were equivalent on postnatal day 7 in males given each of the neonatal treatments. These results suggest that behavioral masculinization in the male ferret results primarily from the neonatal action in brain of T itself, and not from its estrogenic or 5α-reduced androgenic m

ISSN:0028-3835    

DOI:10.1159/000123468

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Two chemical analogs of pergolide were examined to test further the idea that pergolide elevates serum corticosterone concentration in rats by activation of brain dopaminergic receptors. LY116467, which contains an N-methyl substituent in place of the N-n-propyl substituent in pergolide, was less potent than pergolide in lowering brain levels of 3,4-dihydroxyphenylacetic acid (Dopac), the metabolite of dopamine. LY 116467 increased serum corticosterone concentration in rats at a dose of 3 mg/kg (a higher dose than is required for pergolide), and the effect was prevented by spiperone pretreatment. LY141865, which has been reported to differ from pergolide in not activating dopamine-sensitive adenylate cyclase and which was found in this study to have much less affinity for serotonin receptors than does pergolide, increased serum corticosterone in much the same manner as pergolide, only slightly higher doses being required. The effect of LY141865 was prevented by pretreatment with haloperidol but not domperidone. Both haloperidol and domperidone increased serum prolactin concentration when given alone or in combination with LY141865, indicating they were both capable of blocking peripheral (pituitary) dopamine receptors. In contrast, haloperidol but not domperidone caused a marked elevation in brain levels of Dopac and of homovanillic acid and prevented the lowering of these brain dopamine metabolites by LY141865. The ability of LY141865 to increase serum corticosterone concentration was attenuated in rats that had received four daily injections of pergolide mesylate, indicating cross-tolerance had occurred. These results strengthen the hypothesis that activation of brain dopaminergic receptors leads to increased serum corticosterone concentration in rats.

ISSN:0028-3835    

DOI:10.1159/000123469

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The tetradecapeptide, somatostatin (SRIF), is a potent inhibitor on pituitary hormone release, by a direct effect. The immunocytological method was used with the aim of localizing SRIF at the cellular and subcellular levels. Rat pituitaries were fixed and frozen. Ultrathin sections, obtained by cryoultramicrotomy, were incubated with anti-SRIF serum. The antigen-antibody reaction was detected by 4-chloro-1-naphthol. SRIF immunoreactivity was observed in somatotrophs, thyreotrophs and prolactin cells, but not in corticotrophs or gonadotrophs. In immunoreactive cells, SRIF was found in the cytoplasmic matrix, in the secretory granules and in the nucleus distributed primarily in the euchromatin, in the vicinity of the heterochromatin regions. SRIF immunoreactivity was also observed at the plasma membrane. No immunoreactivity was observed when nonimmune serum or anti-SRIF serum incubated with SRIF was used. No modification was observed when anti-SRIF serum incubated with gonadoliberin, thyroliberin or vasopressin was used. These data (1) provide immunocytological evidence for the presence of somatostatin in pituitary gland, and (2) indicate the presence of SRIF peptide in the somatotrophs, thyreotrophs and prolactin cells.

ISSN:0028-3835    

DOI:10.1159/000123470

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Serotonergic control over the reflex oxytocin (OT) release was investigated in anesthetized rats and in conscious rats. The effects of drugs were tested in the first case, on the electrical activity of oxytocinergic cells during suckling and in the second case, on the litter weight gain after 30 min suckling (indirect index of OT release). In rats anesthetized with urethane (1.2 g/kg), intraventricular injection of 1 μg serotonin interrupted the regular pattern of the neurosecretory bursts and milk ejections for about 15-20 min (inhibitory effect of the ‘all-or-none’ type). 10 μg cy-proheptadine or R47465 (serotonergic antagonists) slightly but significantly decreased the mean delay between two neurosecretory bursts without modifying their amplitude and in half the cases, disturbed their periodicity with occasional appearance of very close dual neurosecretory bursts. Pretreatment with p-chlorophenylalanine (PCPA) (250 mg/kg i.p.) did not prevent or affect the regular milk ejection pattern. The inhibitory effect of 5-HT was lengthened by fluoxetine, a 5-HT reuptake inhibitor (1 μl of 10-4M solution into the 3rd ventricle) and prevented by 5 μg R47465. In conscious rats, all the above drugs had an opposite effect. 5-HT and 5-HTP (5-HT precursor) did not affect the milk ejection reflex, whereas serotonergic antagonists and PCPA had an inhibitory effect. Injecting 5-HTP into the PCPA-treat-ed mothers restored their ability to release OT in response to suckling. Hypotheses for these opposite effects are di

ISSN:0028-3835    

DOI:10.1159/000123471

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The effects of streptozotocin-induced diabetes on pituitary growth hormone (GH) content and release from incubated pituitaries were investigated. Male rats were made diabetic by a single injection of streptozotocin (65 mg/kg) and sacrificed by decapitation 15 days later. Pituitary GH concentration was significantly reduced in streptozotocin diabetic rats as compared to that observed in control animals. The amount of GH released from hemipituitaries was also lower in diabetic rats than in controls. Kinetic characteristics of somatostatin (SRIF) inhibition of GH release were not affected by the treatment. These results suggest that the decrease in plasma GH observed by some investigators in streptozotocin diabetic rats is probably due to a deficiency in GH storage and/or synthesis rather than a change in the responsiveness of pituitary GH cells to SRIF.

ISSN:0028-3835    

DOI:10.1159/000123472

出版商:S. Karger AG    

年代:1983

数据来源: Karger