Concentration-dependent effects of muscimol to enhance pulsatile GnRH release from GT1-7 neurons in vitro

Immortalized GT1-7 neurons were used to characterize the effect of muscimol, a GABAA receptor agonist, to enhance pulsatile gonadotropin-releasing hormone (GnRH) release. GT1-7 neurons were grown on Cytodex-3 beads and placed in special superfusion microchambers. The cells were superfused at a rate of 6.2 ml x h-1 with Media 199 (pH 7.35) using a commercially available perfusion system. After a pre-muscimol period of 120 min, the cells were exposed for 5 min to 0.35, 1, 5 or 10 microM muscimol or 5 microM muscimol+20 microM of the GABAA receptor antagonist, bicuculline. Following removal of the muscimol (and bicuculline, in the case of the latter experiment), the superfusion was continued for another 115 min. Sample fractions were collected at 5 min intervals throughout the perfusion. Basal GnRH release from the GT1-7 neurons was pulsatile with an average interpulse interval of 45.4+/-0.5 min and an average pulse amplitude of 191.5+/-22.6 pg x min x ml-1. Our results also demonstrated that the GABAA receptor agonist, muscimol, enhances pulsatile GnRH release from GT1-7 neurons in culture. The response to muscimol was saturable and concentration-dependent with an EC50 of 0.47 microM. The effects of 5 microM muscimol to increase GnRH pulsatility were blocked by co-exposure to the GABAA receptor antagonist, bicuculline. The average GnRH interpulse intervals were 41.7+/-1.8 min, 32.5+/-2.9 min, 30.6+/-0.7 min and 25.5+/-0.4 min in the period following exposure to 0.35, 1, 5 and 10 microM of muscimol, respectively (post-muscimol period). GnRH pulse amplitude (mean-area for each pulse) was increased during exposure to muscimol but not during the pre- or post-muscimol periods. The GABAA receptor antagonist, bicuculline, itself had no effect on pulsatile GnRH release. These results are consistent with previously published reports suggesting that activation of the GABAA receptor stimulates hypothalamic GnRH release in embryonic and neonatal animals.     

Acute isolated myocarditis: Report of a case,with a study of the development of the lesion

The term “acute isolated myocarditis,” now used instead of “acute primary myocarditis,” should designate a disease in which inflammation of the myocardium is the only important active acute lesion in the body. The disease may be due to actual infection of the myocardium, or, as in experimental animals and very probably in man, to the effect of chemical action alone or chemical and other factors acting simultaneously on the heart. In some cases the etiology remains obscure, hence the term “idiopathic.” The disease regularly runs its full course without being recognized, despite the fact that it has been periodically considered and quite well defined in the foreign medical literature during the past thirty-six years. It is only recently that a few reports have appeared in the American literature. Our recent experience with a case prompted us to make a survey of the literature, from which we learned that there is a group of symptoms which seem distinctive. Our survey was extended to include the various chemicals used singly or in combination in the experimental production of acute myocarditis. We wished to know particularly whether experimental myocarditis paralleled acute isolated myocarditis in severity of injury and reaction. Our own case afforded an unusually good opportunity to study the development of the myocardial lesions. By reporting it, and summarizing the important clinical and pathologic characteristics of all the cases in the literature, we hope to facilitate the diagnosis of this elusive disease.     

Effects of cocaine on basal and pulsatile prolactin levels in rhesus monkeys.

OBJECTIVES: Cocaine abuse is often associated with reproductive cycle dysfunction including altered menstrual cyclicity and decreased ovulation rates. Cocaine might also alter prolactin (PRL) secretion, presumably through the effects of this drug on hypothalamic dopamine, the primary factor regulating pituitary PRL secretion. We assessed basal and pulsatile PRL levels to determine whether hyperprolactinemia is associated with cocaine-induced disruption of menstrual cyclicity in rhesus monkeys. METHODS: Normally cycling, drug-na?ve monkeys were studied. Cocaine-treated animals were pair-fed with controls to minimize cocaine-related differences in caloric intake. Twenty-eight monkeys were randomized to receive daily intravenous (iv) infusion of saline or cocaine (1, 2, or 4 mg/kg) on cycle days 2-14. Daily blood samples were obtained through indwelling catheters for measurement of ovarian steroids, gonadotropins, and PRL. Laparoscopy was performed 2 days after the midcycle estradiol surge to document ovulation. Sixteen other monkeys were randomized to receive daily iv infusion of saline or cocaine (4 mg/kg). Blood samples were obtained every 15 minutes for 8 hours in the early (cycle day 1-5), mid- (cycle day 6-10), and late (cycle day 11-15) follicular phase. Plasma was assayed for PRL, and pulses were identified by cluster analysis. RESULTS: All seven control monkeys had laparoscopically confirmed ovulation compared to two of seven monkeys receiving 1 mg/kg, three of seven monkeys receiving 2 mg/kg, and one of seven receiving 4 mg/kg of cocaine hydrochloride. Cycle length was normal in six of seven controls, and in one of seven, two of seven, and two of seven monkeys receiving the 1, 2, and 4 mg/kg of cocaine, respectively. Estradiol levels were significantly higher in controls versus cocaine-treated monkeys, but there was no difference in basal gonadotropin levels during treatment. Mean PRL levels during treatment were significantly lower (P <.05) in controls (4.6 +/- 0.2 ng/mL) as compared to monkeys receiving 1 (6.5 +/- 0.6 ng/mL), 2 (6.1 +/- 0.4 ng/mL), and 4 mg/kg (7.2 +/- 0.6 ng/mL) of cocaine. There was no significant difference in PRL pulse amplitude or frequency between controls and cocaine-treated monkeys during each cycle phase. CONCLUSIONS: Circulating PRL levels were slightly higher in monkeys receiving cocaine during the follicular phase. Although this increase was statistically significant, PRL levels remained well within the euprolactinemic range in cocaine-treated monkeys.     

Azidothymidine (zidovudine) transport by the human placenta

The diagnosis of Acquired Immunodeficiency Syndrome (AIDS) is increasingly made in pregnant women, and the disease may be transmitted to the fetus. Azidothymidine (AZT, Zidovudine) is the one therapeutic agent of some promise in this condition. As there is no information on the transport of this drug by the human placenta, such studies were carried out using the single cotyledon placental perfusion system and human placental vesicles. AZT crossed the placenta readily and bidirectionally. The transfer rate was about 70% that of a freely diffusible reference marker, antipyrine, and was comparable in both directions. There was no evidence of active or carrier-mediated transport and no glucuronidated metabolites of the drug were identified in either maternal or fetal compartments. The authors believe that the drug crosses the placenta by diffusion, consistent with its lipophilicity and transport into various blood cells.     

Cocaine disrupts estrous cyclicity and alters the reproductive neuroendocrine axis in the rat

Although a common drug of abuse, cocaine's effects on cyclic reproductive functions and the neuroendocrine systems regulating these functions have not been studied. Here, we report the effects of cocaine on (1) estrous cyclicity and ovulation rates and (2) the stimulated in vitro release of hypothalamic GnRH and aminergic neurotransmitters directly involved in regulating or modulating GnRH release. Within 7 days of treatment with 10 mg kg-1 day-1 of cocaine HCl subcutaneously, rats demonstrated significant estrous cycle irregularity including repetitive days of estrus and prolonged periods of diestrus. After 6 weeks of treatment, cocaine-treated rats exhibited a 44.3% decrease in ovulation rates. For the in vitro studies, bilaterally ovariectomized rats were injected with cocaine (10 mg kg-1 day-1) or with saline for 2 weeks. Each rat received estradiol benzoate (50 mg kg-1 day-1 s.c.) for 2 days before sacrifice. Hypothalamic slices were prepared, placed in 0.1 ml microchambers and perfused with modified Krebs buffer (pH 7.4) using a programmable perfusion system. Basal release of norepinephrine (NE) and serotonin (5HT) was significantly increased in the cocaine-treated group versus controls. Ten-minute pulses of 10(-7)M progesterone (P4) increase NE and 5HT, but not dopamine (DA), release in the saline-treated group. In contrast, pulses of P4 increased NE, but not 5HT or DA, in the cocaine-treated rats. Ten-minute pulses of 0.1 microM NE increased GnRH release in both saline- and cocaine-treated rats. However, the response to pulsed NE was significantly attenuated in the cocaine-treated group.(ABSTRACT TRUNCATED AT 250 WORDS)