摘要:

Synthetic rat, human, bovine/caprine, porcine and ovine growth hormone-releasing factor (GRF) were tested for their capacity to release growth hormone (GH) by the rat anterior pituitary in vitro. All peptides elicited parallel and dose-dependent increases in GH release and produced similar maximal GH secretion. Rat GRF was 3–6 times more potent in stimulating the release of GH than all other GRFs, while human, bovine/caprine, porcine and ovine GRF had potencies that were not statistically different. The increased potency of both rat GRF(1–27)NH2 and rat GRF(1–23)NH2 when compared to human GRF(1–27)NH2 and human GRF(1–23)NGH2, respectively, suggests that the increased potency of this molecule resides in structural differences in the amino terminal of native GRF. The results demonstrate increased sensitivity of rat pituitary cells for their homologous releasi

ISSN:0028-3835    

DOI:10.1159/000124451

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The uptake and release of γ-[3H]-aminobutyric acid ([3H]-GABA) by the median eminence and the neurointermediate lobe of the pituitary was investigated using sucrose homogenates as crude synaptosomal preparations. Uptake in both areas showed predominantly neuronal specificity and similar Km values, but the median eminence had a considerably greater Vmax value. Release of [3H]-GABA could be stimulated by elevated K+ concentrations, in a Ca2+-dependent manner. Stimulated release was reduced by muscimol, implying the existence of presynaptic autoreceptors in both areas. A number of other transmitters and peptide hormones were demonstrated to have no effect on stimulated release of [3H] GABA in either area

ISSN:0028-3835    

DOI:10.1159/000124452

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Oxytocin (OXY) is a nonapeptide of hypothalamic origin which has defined roles in the female reproductive functions of lactation and labor. However, OXY may have other physiological functions because of its presence in the male and its release in response to stress. Available evidence suggests prostaglandins may stimulate the release of OXY. These experiments sought to determine if the stressors, endotoxin and hemorrhage, would release OXY in the chronically catheterized, freely behaving male rat and what effect the antipyretic and prostaglandin synthesis inhibiting drug, indomethacin, would have on these responses. Endotoxin caused a marked release of OXY from mean baseline levels of 5 pg/ml to mean peak levels of 168 pg/ml. Indomethacin greatly attenuated this increase. In contrast, OXY release in response to hemorrhage of either 22 or 44%of the blood volume of the rat was enhanced by indomethacin. Indomethacin increased the hemorrhage-induced OXY levels about 2-fold over a 2-hour posthemorrhage period. Indomethacin alone had no effect on OXY levels. These data verify that stress is a potent stimulus for OXY release and strengthen the hypothesis that prostaglandins mediate OXY release. The paradoxical effects of indomethacin on OXY release suggest that the prostaglandins may have different effects on OXY release depending upon the evoking stimulus.

ISSN:0028-3835    

DOI:10.1159/000124453

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Angiotensin II analogs with N-terminal extensions were synthesized to examine their effects on the brain and vascular angiotensin II (Ang II) receptors of the rat. Ang II, Crinia-Ang II, Thr.Ala.Gly-Ang II and Val. Ser.Leu.Thr.Ala.Gly-Ang II were all found to elicit drinking and raise blood pressure when given into the cerebrospinal fluid (CSF), and elevate blood pressure when given intravenously. When given intracerebroventricularly, the order of potency of the peptides in eliciting blood pressure and drinking responses was: Ang II (100%) = Crinia-Ang II (100%) &rt; Thr.Ala.Gly-Ang II (10% blood pressure, 15% drinking) > Val.Ser.Leu.Thr.Ala.Gly-Ang II (5%). The order of pressor potency did not change when the Ang II analogs were given intravenously, but compared with the central effects, there was a marked difference in the relative potencies of the peptides. The potencies were: Ang II (100%) &rt; Crinia-Ang II (80%) &rt; Thr.Ala.Gly-Ang II (60%) &rt; Val.Ser.Leu.Thr.Ala.Gly-Ang II (20%). Blood pressure and drinking responses produced by all of these peptides were markedly attenuated by the Ang II receptor antagonist, [Sar’Thr8] Ang II. These findings indicate a difference in the Ang II receptors present in the brain and the periphery. However, no differences were noted between the central Ang II receptors mediating the pressor responses and the central Ang II receptors stimulating drinking behavio

ISSN:0028-3835    

DOI:10.1159/000124454

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Food consumption elicited by injection of norepinephrine (NE) into the paraventricular nucleus (PVN) of satiated rats has been shown to be dependent on the glucocorticoid corticosterone. To determine the specific nature of this dependence of NE-induced feeding on corticosterone, the efficacy of PVN-injected NE and its interaction with peripherally administered corticosterone was examined in adrenalectomized rats. NE, at doses ranging from 10 to 160 nmol, failed to elicit a reliable feeding response in these adrenalectomized animals. This loss of noradrenergic responsiveness developed at least as early as 4 h after adrenalectomy and continued until the end of the test sequence 6–8 weeks post-surgery. Single subcutaneous injections of corticosterone, administered to adrenalectomized rats, significantly restored the NE feeding response when injected 15–120 min prior to NE PVN injection, but not when administered 5 min before. Corticosterone was effective at doses of 0.5–4.0 mg/kg. Tests with other steroid hormones, namely, the synthetic glucocorticoid dexamethasone, the mineralocorticoid deoxycorticosterone, and the gonadal hormones testosterone and progesterone, were generally ineffective in restoring the sensitivity of the PVN to noradrenergic stimulation. Radioimmunoassay of circulating corticosterone in adrenalectomized rats, as a function of dose and time after injection of corticosterone, indicated that physiological levels of the hormone, at least 3 µg%, are required for a patent behavioral effect. These findings demonstrate a specific, sensitive, and rapid dependence of the PVN α2-noradrenergic eating response on circulating cortico

ISSN:0028-3835    

DOI:10.1159/000124455

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The effects of cortisol on protein synthesis in distinct brain regions were studied. Hormone administration produced increases in tubulin and actin content in the soluble fraction isolated from septum and hippocampus. Therefore, the poly(A)RNAs were isolated from the same brain regions and their translational capacity was tested in a heterologous cell-free system. Poly(A)RNAs from cortisol-treated animals, as compared to control animals, had a stimulatory effect on 35S-methionine incorporation into tubulin and actin. Thus, our results suggest that cortisol treatment increases the amount of mRNAs coding for tubulin and actin. More importantly, this study indicates that the molecular mechanism of glucocorticoid action in the brain involves modulation of protein synthesis.

ISSN:0028-3835    

DOI:10.1159/000124456

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Using slices of rat hypothalamus maintained in vitro, we have examined release of oxytocin and vasopressin under conditions of increased neuronal activity. We report here that when the supraoptic or paraventricular nucleus is depolarized with high K+ solutions, hormone is released into areas close to the nucleus. Similar experiments with guinea pig hypothalamus suggest that neurophysin may also be co-released with oxytocin and vasopressin. Use of acetylcholine to selectively stimulate vasopressin neurones appears to evoke a rise in local release of vasopressin but not oxytocin. These results suggest that under conditions of increased neuronal activity, hormones normally secreted from the neurohypophysis are secreted locally into the hypothalamus.

ISSN:0028-3835    

DOI:10.1159/000124457

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Many reports indicate that prolactin has a role in puberty occurrence. The present study was developed to evaluate the action of pituitary grafts on puberty. Female rats grafted on day 21 with ‘adult’ (90 days old) or ‘young’ (21 days old) pituitaries showed precocious vaginal opening and first estrus. The puberty advancement induced by ‘adult’ transplants was due to an increase in plasma prolactin values and can be blocked by bromocriptine treatment. The puberty advancement induced by ‘young’ transplants was not associated with increased prolactin levels and cannot be blocked by bromocriptine. These results suggest the existence of two possible mechanisms in precocious puberty induced by pituitary grafts: a prolactin-dependent one and another one not directly related

ISSN:0028-3835    

DOI:10.1159/000124458

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Studies were undertaken to (1) examine the effects of hyperprolactinemia on the frequency and amplitude of pulses of LH, and (2) determine if changes in pituitary sensitivity to LHRH were involved in the prolactin-induced suppression of LH secretion. Rats were bilaterally ovariectomized (day 0). Ovine prolactin (4 mg/kg body weight, subcutaneously) or vehicle was administered every 8 h beginning at 09.00 h on day 4 after ovariectomy and continuing until 09.00 h on day 6. On day 6, between 07.00 and 09.00 h all animals received a right atrial cannula, using ether anesthesia. In experiment I blood samples were taken at 10-min intervals beginning at 12.00 h on day 6, for a total of 180 min. To test the effect of hyperprolactinemia on pituitary responsiveness (experiment II) animals received an intravenous injection of LHRH (25 ng/100 g body weight) after the 180-min and again after the 240-min sample. Blood was drawn every 10 min for a total of 300 min. Serum was assayed for LH. Hyperprolactinemia altered the pattern of pulsatile secretion of LH. Treatment with ovine prolactin produced a decrease in both the frequency and amplitude of the LH pulses compared to values found in control animals. However, no differences in pituitary responsiveness between hyperprolactinemic and control animals were found at the dose of LHRH given. Thus, the prolactin-induced suppression of pulsatile secretion of LH was not apparently a result of alterations in the sensitivity of the pituitary to LHRH. From these studies we suggest that hyperprolactinemia directly affects a hypothalamic site which ultimately alters the LHRH pulse generator, thereby changing the secretion of LHRH.

ISSN:0028-3835    

DOI:10.1159/000124459

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Responses to estrogen differ between the sexes, yet sex differences in specific binding of estradiol (E2) to its receptor are not observed consistently. Dopaminergic treatment has been shown to increase binding of 3H-E2 in selected brain areas and anterior pituitary in the female rat, and the dopaminergic system is sexually differentiated. In order to determine whether or not dopaminergic stimulation might induce sex differences in 3H-E2 binding, male and female gonadectomized-adrenalectomized rats were pretreated either with bromocriptine, a dopamine agonist, or with diethyldithiocarbamate (DDC), an inhibitor of dopamine β-hydroxylase. DDC was used in order to increase endogenous release of dopamine. After such acute dopaminergic treatment, specific binding of 3H-E2 in nuclear and extranuclear fractions of 6 brain areas and pituitary in vivo was determined 1 h after intravenous injection of Η-E2 (1 µg/kg body weight). Administration of either bromocriptine or DDC increased specific 3H-E2 binding to nuclear and extranuclear fractions of basal hypothalamus and anterior pituitary from female but not from male rats, thus inducing sex differences in binding in these two tissues. Bromocriptine also increased specific binding in the pineal in females. Total binding was increased in a crude membrane fraction (P2) from pituitary of female but not of male rats after administration of DDC, but the percent of extranuclear specific binding found in the P2 fraction was decreased after DDC in both males and females. The findings suggest that dopaminergic stimulation may induce sex differences in 3H-E2 binding by increasing binding in some brain areas and anterior pituitary in females but not in mal

ISSN:0028-3835    

DOI:10.1159/000124460

出版商:S. Karger AG    

年代:1986

数据来源: Karger