...Carlos M. Villegas-Gabutti; Gisela E. Pennacchio; Laura Vivas; Graciela A. Jahn; Marta Soaje Background/Aims: During late pregnancy, the blockade of progesterone action by mifepristone (Mp) treatment induces a dopaminergic tone fall that enables naloxone (NAL) administration to release pituitary...

...) in ovariectomized rats. However, the mechanisms underlying this action remain unclear. We examined the effects of naloxone (NAL), a specific opioid antagonist, on the suppression of pulsatile LH secretion by ghrelin to determine whether β-endorphin (β-END) is involved in this suppressive effect. Methods: Ghrelin...

...Carlos Villegas Gabutti; Marcelo Ezquer; Ricardo Deis; Cristina Maldonado; Marta Soaje Background/Aims: The antiprogesterone mifepristone facilitates prolactin release, an effect enhanced by administration of the opioid antagonist naloxone. The present study explores ultrastructural changes...

...Gregory I. Hockings; Jeffrey E. Grice; Margaret M. Walters; Georgina V. Crosbie; David J. Torpy; Richard V. Jackson Naloxone stimulates pituitary-adrenal function by blocking an endogenous inhibitory opioidergic tone which modulates pituitary adrenocorticotropin (ACTH) release. In animals...

..., naloxone, on ceruletide-induced ACTH secretion in man. In 6 normal subjects, basal ACTH and cortisol plasma levels were significantly suppressed 3 h after loperamide administration (16 mg, orally) from 5 ± 0 to 2 ± 0 pmol/l and from 356 ± 44 to 154 ± 16 nmol/l. After stimulation with 8 ng ceruletide/kg...

... and corticotropin-releasing hormone (CRH) in these processes. Adult ovariectomized rhesus monkeys bearing a chronic cannula in the lateral ventricle for intraventricular (i.c.v.) infusion were used. In experiment 1, the effects of 5-hour i.c.v. infusions of saline (n = 7), AVP (50 µg/h, n = 7), naloxone (2 mg bolus...

...-induced prolactin elevation and blood samples were collected every 10 min for prolactin determinations. The opiate antagonist, naloxone (n = 5), reduced serum prolactin in a dose-related manner with a mean IC 50 of 1.5 ± 0.6 µg/kg/min. The OT (n = 4), SP (n = 4) or VIP (n = 4) antagonists did not reduce...

... or interval. Naloxone administration (2.5 mg bolus followed by a 1 mg/h infusion lasting 4-8 h) completely (n = 4) or partially (n = 2) blocked the effects of E 2 on MUA volley interval in 6 of the 8 monkeys, and was without effect in the remainder. In contrast, however, naloxone had little or no effect...

... hormone secretion (MUA volleys). Administration of naloxone, an opioid receptor antagonist, at a rate of 1.0 mg/kg/h for 2 h resulted in shorter (p < 0.05) intervals between MUA volleys than during the control period (61.6 ± 0.7 vs. 92.5 ± 7.2 min) in animals treated with progesterone and estradiol...

... through day 65. They were injected subcutaneously with saline, 0.25 or 1.0 mg/kg body weight naloxone and sacrificed 20 min later. Another group of immature males was castrated, implanted with testosterone-filled capsules and tested with naloxone 4 days later. The peripubertal increase in testosterone...

... and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements. Opioid binding sites Chondrocytes Growth plate Autoradiography β-Endorphin Naloxone Morphine Original Paper...

...Ida Gerendai; Ágnes Nemeskér; Valér Csernus Previous studies indicate that 7 days after testicular administration of naloxone, serum testosterone (T) concentration and basal T secretion in vitro decrease significantly. In neonatal rats, short-term (2 h) intratesticular treatment with 0.3 µg ( D...

... the course of aging from 14 to 24 months of age could (1) influence the age-related changes that occur in basal serum levels of LH and in the LH response to GnRH or to naloxone stimulation at 16, 18 and 20 months of age, and (2) delay the onset of the postreproductive constant estrous-anovulatory state...

...Darrell W. Brann; Pedro L. Zamorano; Carla D. Putnam-Roberts; Virendra B. Mahesh Previous studies in the male rat have demonstrated that GABA acting via GABAB receptors can abolish naloxone-induced LH secretion. The purpose of the present study was to determine if an analogous situation exists...

... of endogenous opioid peptides causes this slowing of pulsatile LH secretion, the ability of naloxone administration to reverse the fasting-induced suppression of LH secretion was tested. For this study, 6 adult male rhesus monkeys, with indwelling femoral and jugular venous catheters, were maintained on tether...

...Kazuo Otake; Kunikazu Kondo; Yutaka Oiso We examined the effects of γ-aminobutyric acid (GABA) and naloxone, a potent opioid antagonist, on arginine vasopressin (AVP) secretion in conscious rats in order to study the relationship of GABA and endogenous opioid peptides in the regulation of AVP...

... of aberrant regulation of hypothalamic GnRH secretion in experimental uremia, we examined basal secretion of GnRH from mediobasal hypothalamus (MBH) in vitro and the GnRH-secretory responses to naloxone, an opiate receptor antagonist in experimental uremia. Using a static incubation system, adult male rats...

... to the opioid antagonist naloxone at various ages in both sexes. To determine the timing of the pubertal LH rise in the presence of constant inhibitory steroid feedback, male and female lambs (n = 5 each) were gonadectomized at 3 weeks of age and implanted with a Silastic capsule of estradiol. They were...

... was evaluated with the administration of the opioid antagonist naloxone. ANG II (i.v. infusion for 60 min of successively increasing doses of 4, 8 and 16 ng/kg min; each dose for 20 min) was given to 7 normal men, alone or together with naloxone (10 or 20 mg injected i.v. just before ANG II infusion). In all...

... (1.25 mg/day). At the same time, the activity of the endogenous opioid system was evaluated, as well as the LH response to the 4-hour infusion of the opioid antagonist naloxone (1.6 mg i.v. bolus followed by 1.6 mg/h). Both before and during estrogen administration, plasma FSH levels were similar...