摘要:

The main purpose of this study was to evaluate changes in plasma arginine vasopressin (AVP) associated with arterial baroreceptor deafferentation. Food and water intake of sham-operated (SO) rats was matched to that of sinoartic denervated (SAD) rats, and blood samples were collected from groups of SAD and SO rats 15 min, 1–4 h, 24 h and 4–7 days after operation. Plasma AVP was 2–4 times higher in SAD than SO rats at each of the times studied during the 1st week (p < 0.001); at those times no significant differences in hematocrit, plasma sodium or osmolality were found. Three weeks after surgery, plasma AVP was similar in both groups of rats. Mean arterial pressure, measured in additional groups of rats, was approximately 35 mm Hg higher in SAD than SO rats for the first 4 postsurgical hours, remaining about 20 mm Hg higher at the later times. Administration of an AVP pressor antagonist to SAD rats caused a small (8–11%), statistically significant reduction in the elevated pressure of SAD rats during the first 4 postsurgical days. Thus, AVP contributes modestly to the elevation of arterial pressure caused mainly by neurogenic mechanisms in SAD rats during the early postoperative period. Ingestive behavior was monitored in additional SO and SAD rats. SAD rats had significantly reduced food and water intake for 5 days after surgery, however, by day 6 intake was comparable to that of SO rats. Preoperative body weight was not regained until 2 weeks after surgery. The results indicate that sinoaortic baroreceptor reflex pathways interact with systems regulating AVP secretion and ingestive-metabolic processes as well as with those autonomic systems directly affecting cardiovascular f

ISSN:0028-3835    

DOI:10.1159/000124473

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Studies were conducted to determine if the inhibitory effects of chronic hyperprolactinemia on sexual behavior in male rats occur through reduced sexual arousal as opposed to reduced erectile function. Pituitary-grafted (hyperprolactinemic) and sham-operated, gonadally intact male rats were given standard tests of copulatory behavior, mounting behavior tests after genital anesthetization and penile reflex tests while restrained in a supine position. Beginning 7 days after pituitary transplantation, the number of erections displayed in penile reflex tests was significantly reduced in the pituitary-grafted animals. Increased intromission latencies and reduced intromission rates in tests of copulatory behavior were also observed at this time. Beginning 3–4 weeks after surgery, mounting rates were inhibited in hyperprolactinemic animals in both the copulatory behavior tests and tests of mounting behavior after genital anesthetization. Prolactin levels were significantly elevated in the pituitary-grafted animals, but serum testosterone levels were unaffected. To determine if the effects of hyperprolactinemia on erectile function occurred through changes in supraspinal input to neurons in the spinal cord controlling erectile function, pituitary-grafted and sham-operated male rats were subjected to spinal transection (between vertebral levels T6 and T9). Beginning 7 days later, penile reflex performance was re-examined. Hyperprolactinemic animals displayed significantly fewer erections during the initial test, but not in tests performed 10 and 13 days after spinal transection. The pituitary-grafted animals also showed a significant reduction in latency to the first erection with each successive test, suggesting a delayed recovery from increased supraspinal inhibitory input. These results show that hyperprolactinemia inhibits both sexual arousal and erectile function, and suggest that the inhibition of erectile function occurs through an effect of the hyperprolactinemic state at a supraspinal level within the central nervous syste

ISSN:0028-3835    

DOI:10.1159/000124474

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

In order to clarify the effects of endogenous opiate peptides on the vasopressin system, we have investigated the presence of different opiate receptor subtypes in the neurohypophysis by radioreceptor assay and autoradiography. [3H]-etorphine binding to membrane preparations revealed the presence of high- and low-affinity binding sites (KD, 1.2 nM and 8.1 nM). Displacement of [3H]-etorphine by opiate receptor subtype-specific ligands gave the following results: (1) the preferential mu agonists DAGO (Tyr-D-Ala-Gly-NMe-Phe-Gly-oL) and the tetrapeptide morphiceptin did not displace etorphin; (2) the preferential sigma receptor agonists DADLE (D-Ala2, D-Leu5-enkephalin) or DSTLE (D-Ser2, Leu5, Thr6-enkephalin) and β-endorphin, a preferential agonist of the epsilon receptor, displaced [3H]-etorphine from its low-aiïinity site only, and (3) dynorphin 1–8, a preferential kappa agonist, displaced [3H]-etorphine from its high-affinity binding site. Film autoradiography of neurohypophyseal sections incubated with [3H]-etorphine showed a displacement of 30% of the labeled ligand by unlabeled dynorphin 1–8. Exposure of rat neurointermediate lobes in organ culture to dynorphin 1–8 caused a small but significant stimulation of vasopressin release. These results demonstrate the existence of dynorphin 1–8 sensitive opiate receptors of the kappa subtype in the neurohypophysis and their possible involvement in vasopressi

ISSN:0028-3835    

DOI:10.1159/000124475

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The in vitro release of stored intracellular rat growth hormone (rGH) in response to several secretagogues suggests the functional division of rGH storage into at least two ‘compartments’ or ‘pools’. The first is an immediately releasable compartment whose response is brief. The second is a compartment which responds to more prolonged secretory demands. These observations are consistent with either a single, homogeneous population of somatotrophs, each of which exhibits functional compartmentalization of storage, or with heterogeneous populations of somatotrophs, each family of which provides one of the observed responses. We sought anatomical correlates of this functional compartmentalization using a perifusion/morphometric system which permitted examination of the first model while not excluding the second model. We selected for study an established perifusion protocol whose behavior was consistent and whose previous results suggested phases of both filling and emptying of the immediate release pool. Five parallel perifusions of pituitary fragments were run. The fifth perifusion was used to monitor rGH release and to confirm that the experiment had behaved in standard fashion. The first pituitary chamber was dismantled during basal perifusion to obtain tissue for microscopy, the next during exposure to 25 nM SRIF, the third during exposure to both 25 nM SRIF and 1 mM (Bu)2cAMP, and the fourth shortly after the rapid release which followed SRIF withdrawal. Somatotroph granulation was decreased by 54% in the presence of SRIF, and then increased by 45% with the addition of (Bu)2cAMP. The intracellular distribution of granules also fluctuated in relation to the stimulatory and inhibitory secretagogues. In addition, secondary lysosomes increased by 549% during SRIF-induced inhibition of rGH release. Cell volume was decreased by 37% in the presence of 25 nM SRIF; the addition of (Bu)2cAMP did not reverse this SRIF effect. We conclude that the in vitro release phenomenon we have termed the ‘immediate release pool’ has an anatomic correlate in juxtamembrane granules, that inhibition of rGH release is accompanied by a significant increase in secondary lysosome activity, that while heterogeneous populations of somatotrophs probably exist, individual cells possess a range of responses consistent with functional compartmentalization, and that rGH release involves not only granule movement between anatomically demonstrable compartments, but in addition, major and rapid changes in somatot

ISSN:0028-3835    

DOI:10.1159/000124476

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The present study examines the effect of progesterone (P) on in vitro LHRH release from hypothalamic fragments from intact adult rats throughout the estrous cycle. Estrous cyclicity was monitored by daily vaginal smears, and animals which exhibited at least two consecutive 4-day estrous cycles were used. Animals were sacrificed between 10.00 and 13.00 h and the mediobasal hypothalamic-preoptic area-suprachiasmatic nucleus units were removed and transferred into superfusion chambers (one unit/chamber). Following a 2-hour control period, in which the spontaneous LHRH release was established, P (10 ng/ml) was infused in an intermittent mode (10 min-on, 20 min-off). Effluents were collected at 10-min intervals and LHRH concentrations were determined by RIA. The spontaneous LHRH release from control preparations was episodic throughout all stages of the estrous cycle with a significant low release rate and low LHRH amplitude only during estrus. Interestingly, intermittent infusion of P significantly stimulated LHRH release solely in hypothalamic fragments derived from proestrous rats. The P-stimulated LHRH release during the 1st-hour period after P infusion was significantly higher (p < 0.05) than that observed in the control preparations during the same time period as well as from its own basal pre-P values (1-hour post-P: 4.26 ± 0.96 vs. 1-hour control and pre-P: 2.34 ± 0.38 and 2.32 ± 0.57 pg/10 min, respectively). P administration did not stimulate in vitro LHRH release during the other stages of the estrous cycle. These results demonstrate that P stimulates in vitro LHRH release only during the proestrus stage of the estrous cycle, further supporting the idea that preovulatory rise in blood P levels may play an important role in activating the rat LHRH neural apparat

ISSN:0028-3835    

DOI:10.1159/000124477

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Characteristics of pancreatic TRH-degrading activity were determined using [L-proline-2,3-3H] TRH and [L-histidine-2,5-3H] TRH as tracers and thin-layer chromatography to detect, identify and quantify TRH metabolites following incubation of tritiated TRH with pancreatic homogenates. The apparent Km of pancreatic enzymes was 2.2 10–5M, the V, 45 pmol/min, and the apparent specific activity, 62.3 ±3.45 pmol/min/mg total protein. In conditions of enzyme saturation, the percent of TRH degraded was found to be similar to the sum of degraded products formed (TRH-OH and His-Pro). Based on the chromatographic identification of metabolites, the presence of a deamidase pathway and a non-deamidase pathway in the TRH-degradation process of the pancreas was postulated. To better characterize the corresponding pancreatic enzymes, active site-directed inhibitors were then used and metabolites yielded were compared to those obtained in the same experimental conditions using plasma as enzyme source. The detection of His-Pro diketopiperazine among the metabolites was of especial interest since this biologically active metabolite was also found in the pancreas as an endogenous peptide and reported to be either a TRH degradation product or derived from sources other than just TRH. However, in presence of inhibitors, His-Pro diketopiperazine was only detected using plasma as enzyme source. Nevertheless, a pancreatic contribution to plasma TRH-degrading activity cannot be discard

ISSN:0028-3835    

DOI:10.1159/000124478

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

A significant increase of cell multiplication in inoculated ascitic and solid tumors was demonstrated in both DBA/2 and C57BL/6 mice as well as in Wistar rats after radiofrequency lesions in the median hypothalamus (ventromedial and dorsomedial nuclei; part of arcuate nucleus). The following tests were performed: mitotic and metaphasic index, doubling time of tumor, incorporation of tritiated thymidine into DNA, cell cycle parameters and growth fraction. The increased rate of cell proliferation measured was predominantly due to the higher speed of DNA biosynthesis with a minor contribution by an increase of the growth fraction. In the animals with hypothalamic lesions we demonstrated a slight decrease in the secretory activity of the adenohypophysis. Because it is generally stated that failure of hypophysis function hinders cell multiplication in normal and neoplastic tissues, we think that heightened cell proliferation after hypothalamic lesions is due to suppression of an inhibitory mechanism located in the hypothalamus and which is independent of the hypophysis.

ISSN:0028-3835    

DOI:10.1159/000124479

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The role of central adrenergic receptors in the control of vasopressin release was studied in the conscious rat. Norepinephrine (10 µg) and the alpha-1 agonist, phenylephrine (50 µg), administered intracerebroventricularly resulted in significant increases in the plasma vasopressin concentration and blood pressure. The alpha-2 agonist, BHT 933 (50 µg) and the beta agonist, isoproterenol (10 µg) both caused a significant decrease in the plasma vasopressin concentration with only small changes in blood pressure. The central administration of the alpha-1 antagonist corynanthine (20 µg) had no effect on the plasma vasopressin concentration; however, increases in plasma vasopressin levels were observed when either the alpha-2 antagonist yohimbine (20 µg) or the beta antagonist propranolol (20 µg) were given. It is concluded that central noradrenergic pathways may play an important role in the control of vasopressin release and that this control may involve alpha-1, alpha-2 and beta adrenorec

ISSN:0028-3835    

DOI:10.1159/000124480

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The influences of morphine and naloxone on hypothalamo-pituitary-adrenocortical (HPA) function were studied in the rat to investigate further the role of opioidergic mechanisms in the control of the secretion of corticotrophin and its hypothalamic releasing factor (CRF). Morphine not only caused rises in hypothalamic CRF content and plasma ACTH concentration but also potentiated the HPA response to stress. Its effects were antagonized by naloxone which, when given alone, did not influence basal plasma concentrations of ACTH and corticosterone but which inhibited, in a dose-dependent manner, the release of both of these hormones which normally occurs in response to stress. Naloxone also attenuated the exaggeration in stress-induced HPA activity but did not affect the increases in plasma ACTH concentration which followed adrenalectomy. The findings suggest that opioidergic mechanisms may be involved in the regulation of the HPA response to stress.

ISSN:0028-3835    

DOI:10.1159/000124481

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The effects of surgery and red light on prolactin (Prl) secretion were investigated in cycling and in pseudo-pregnant (PSP) rats. Secretion patterns of Prl were determined at hourly intervals from 07.00 to 22.00 h. Different regulatory mechanisms for Prl secretion were hypothesized for three time periods: a nocturnal (07.00–11.00 h), a prediurnal (14.00 -17.00 h), and a diurnal (19.00–22.00 h) period. The results demonstrate that red light can affect significantly Prl secretion, in particular nocturnal and prediurnal Prl secretion in estrous, diestrous day 1 and PSP rats. The effect of surgery varied with the time of the day and was dependent upon whether the animals, during the dark period, were maintained under full darkness or constant red dim illumination. In PSP rats the regulation of Prl secretion was different for the three time periods. In PSP day 0 rats there was a prediurnal surge of Prl secretion, comparable in timing and regulation to a prediurnal surge in estrous rats. This prediurnal surge was not evident on the other days of PSP. The regulation of nocturnal as well as diurnal Prl secretion was similar in PSP rats, but differed from cycling rats. The afternoon surge of Prl secretion on proestrus lasted the full afternoon and was basically one surge, distinct from all other surges. In diestrous rats Prl levels were low but showed a circadian variation. In summary, the effects of red light and surgery on Prl secretion varied with the physiological state and with the time of the day, indicating that the regulation of Prl secretion is complex and multimodal in nat

ISSN:0028-3835    

DOI:10.1159/000124482

出版商:S. Karger AG    

年代:1986

数据来源: Karger