Evidence of specific benzodiazepine binding to myometrial membrane preparations from human pregnant uterus

The muscle relaxant effect of benzodiazepines (BDZ) is widely held to be mediated at central as well as at peripheral level. In this study we report that crude membrane preparations from the myometrium of pregnant women possess binding sites for [3H]-RO 5-4864, specific ligand for the peripheral type of BDZ receptor. Scatchard analysis shows a high affinity binding site (KD = 3.1 +/- 1.2 nM) and a class of low affinity binding sites (KD greater than 30 nM). Displacement experiments show that various BDZ are differently effective in inhibiting [3H]-RO 5-4864 binding: RO 5-4864 greater than diazepam greater than flunitrazepam greater than lorazepam greater than chlordiazepoxide. In conclusion, these data seem to demonstrate that human myometrium possesses specific binding sites of 'peripheral type' for BDZ. It may be suggested that these binding sites are involved in mediating the myometrial relaxant effect exerted by BDZ. Thus, peripherally active BDZ could be used as tocolytic agents, avoiding BDZ central effects.

Sex steroids modulate prolactin response to naloxone in postmenopausal women

To evaluate whether ovarian steroids modify the prolactin (PRL) response to opioid receptor blockade, the effects of naloxone infusion (1.6 mg/h for 4 h) on PRL secretion were studied in 5 postmenopausal women. Naloxone infusion was performed in basal conditions and after chronic oral treatment with conjugated estrogens (CE) (1.25 mg/day, for 20 days) or CE plus medroxyprogesterone acetate (MPA) (10 mg/day, for 20 days). Under basal conditions, 17 beta-estradiol, estrone, gonadotropin, and PRL plasma levels were in the normal range for postmenopausal women, and naloxone failed to affect PRL secretion. Naloxone induced a significant PRL increase after CE treatment alone (p less than 0.001) or in combination with MPA (p less than 0.001). The increase was significantly higher (p less than 0.05) after CE + MPA treatment than after CE treatment alone. These data suggest that steroids modulate the stimulatory effect of naloxone on PRL secretion in postmenopausal women.

Fibrinopeptide A plasma levels during low-estrogen oral contraceptive treatment

In a group of healthy women taking oral contraceptives containing 30 micrograms ethinylestradiol combined with two different progestogens (desogestrel and gestoden), Fibrinopeptide A (FPA) plasma levels were evaluated both before and after 3, 6 and 9 months of therapy. FPA levels, which represent an index of thrombin action in vivo, were also determined in untreated subjects during the follicular and the luteal phases of the menstrual cycle. While no modifications of FPA levels were found during the menstrual cycle, a significant increase of this peptide was observed during oral contraceptive treatment. These data suggest that low-dose oral contraceptives, by enhancing the rate of conversion of fibrinogen to fibrin by thrombin, increase the risk of venous thrombosis. Since some mechanisms which compete with the thrombin activity are also increased by oral contraceptives, the significance of this change in the induction of thrombosis cannot be completely clarified.

Aminophylline treatment of preterm labor

Prevention of neonatal mortality linked to prematurity may be achieved by treating preterm labor, thus allowing fetal lungs to spontaneously develop, or by administering drugs able to enhance pulmonary maturation. The methylxantine derivative aminophylline has been reported to reduce uterine contractility and increase the concentrations of saturated phosphatidylcholine in fetal lungs. Its effectiveness in treating preterm labor and preventing respiratory distress syndrome (RDS) has been evaluated in comparison to the widely used drug ritodrine. In 39 pregnant women with preterm labor the efficacy of aminophylline and ritodrine in delaying the delivery seemed similar. However, while two of the babies born from ritodrine treated mothers died because of RDS, all babies born from aminophylline-treated mothers survived. These data might then confirm the effectiveness of aminophylline treatment to prevent RDS.

Evidence that estrogens inhibit LH secretion through opioids in postmenopausal women using naloxone

To evaluate whether ovarian steroid environment may modify endogenous opioid activity at hypothalamic-pituitary level, the effects of naloxone infusion (1.2 mg/h for 4 h) on gonadotropin secretion were studied in 5 postmenopausal women who had natural menopause 3-5 years before the study. In addition, naloxone infusion was repeated in the same subjects after chronic oral treatment with conjugated estrogens (1.25 mg/day in two divided doses for 20 days). Before treatment, both the circulating levels of estrogens and plasma gonadotropins were in the normal range for postmenopausal women and naloxone infusion did not induce any significant modification of gonadotropin secretion. In contrast, after estrogen therapy, and the consequent rise in estrogen plasma levels, naloxone infusion induced a significant LH increase (p less than 0.01) starting during the last hour of treatment. These findings seem to confirm that endogenous opioid peptides may modulate the inhibitory effect exerted by estrogens on LH secretion, in humans.

Ultrasound and estradiol plasma levels in threatened abortion

Ultrasound examination and unconjugated estriol assay were performed in 111 women with threatened abortion between the 6th and the 20th week of pregnancy. In viable pregnancies, fetal echoes and fetal heart movements were always observed by sonar from the 10th week onward and estradiol levels always increased above 30 pg/ml from the 13th week. Both ultrasound and estriol assay showed high percentages of uncertain prognostic indication on pregnancy outcome when examinations were performed during the first weeks of pregnancy. However, in the same period estriol levels higher than 30 pg/ml were always correlated with the favourable outcome of pregnancy, since no abortion occurred in subjects with detectable estriol values. During the second trimester ultrasound and estradiol results were normal in all viable pregnancies, while they were abnormal in 71.4% of pregnancies which failed to continue. Estriol values were always undetectable when fetuses could not be identified by sonar or they were dead. These data seem to demonstrate that both methods have similar prognostic value in patients with threatened abortion. However both sonar examination and estriol levels sometimes failed in predicting subsequent pregnancy interruptions, suggesting that abortions were not related to either fetal or placental alterations.

Effects of the GABAergic drug, sodium valproate, on the prolactin release evoked by pharmacological stimuli in normal women

Sodium valproate (DPA or Na-dipropylacetate), an anticonvulsant drug activating the endogenous GABAergic system, was administered orally at the dose of 400 mg to seventeen normal women 1 h before intravenous injections with three drugs which stimulate prolactin (PRL) release: TRH (200 micrograms bolus; six subjects); domperidone (5 mg bolus; six subjects); and sulpiride (5 mg bolus; five subjects). DPA pretreatment significantly blunted PRL response to both domperidone and sulpiride injections without affecting the PRL response to TRH. In particular, the quantitative PRL secretion (areas under curves) following domperidone and sulpiride tests appeared significantly reduced after DPA treatment in comparison to placebo (P less than 0.02 and P less than 0.01 for domperidone and sulpiride respectively). These results indicate that the pharmacological enhancement of the endogenous GABAergic system by DPA may blunt PRL response to both central and peripheral dopamine receptor blockade. These observations suggest that a GABAergic pathway inhibiting PRL secretion at the hypothalamic level competes, at least in part, with the dopaminergic system. Conversely, the lack of any effect of DPA on PRL response to TRH seems to suggest that pituitary TRH receptors are independent of any GABAergic control.

Pharmacological activation of gamma-aminobutyric acid-system blunts prolactin response to mechanical breast stimulation in puerperal women

To evaluate whether the gamma-aminobutyric acid (GABA)ergic system participates in the control of PRL secretion during the puerperium, different doses of sodium valproate (DPA), a drug that increases endogenous GABA activity, were administered orally to puerperal women who did not wish to breast feed their infants. Two groups of five women were each given DPA in doses of 400 and 800 mg, respectively. PRL levels were measured in plasma samples collected before and after drug administration. Another group of five puerperal women was treated with 800 mg DPA 60 min before mechanical breast stimulation using an electric breast pump for 15 min. Circulating PRL levels were measured in samples obtained before, during, and after breast stimulation. No drug-associated side effects were observed. After placebo administration, no significant variations in plasma PRL levels occurred in any subject. The lower dose of DPA (400 mg) induced a slight decrease in plasma PRL levels, but 800 mg of the drug induced a significant fall (P less than 0.05 vs. baseline values) in PRL, with a maximum percent decrease (68.2 +/- 4%) 180 min after DPA treatment. Mechanical breast stimulation performed after placebo treatment induced a significant increase (P less than 0.01) in plasma PRL levels, with peak values (37 +/- 10% above baseline values) 10 min after the onset of stimulation. When DPA was administered to the same women, a significant decrease (23 +/- 3%) in plasma PRL occurred during breast stimulation. Thereafter, PRL values continued to fall in spite of breast stimulation. PRL levels were significantly decreased after DPA treatment compared to both basal values (P less than 0.01) and the levels found in the same patients during control tests (P less than 0.05). These results demonstrate that enhancement of endogenous GABAergic tone induced by DPA significantly decreases basal PRL levels and blunts PRL release after mechanical breast stimulation. In agreement with animal data, a possible physiological role of GABA in the control of PRL release during puerperium may be suggested.

The effects of the gabaergic drug, sodium valproate, on prolactin secretion in normal and hyperprolactinemic subjects

To find out whether the gamma-aminobutyric acid (GABA)ergic system affects PRL secretion in humans, sodium valproate (DPA or Na-dipropyl-acetate), a drug inducing increase of endogenous GABA, was administered to 20 normal and 15 hyperprolactinemic subjects. PRL circulating levels were measured by RIA in the samples obtained after acute oral treatment with 400 mg DPA. A significant decrease (P less than 0.01) in comparison with basal levels was observed in normal women from 30-180 min after drug administration. DPA treatment also lowered blood PRL levels in hyperprolactinemic subjects (seven females) without evidence of pituitary tumor. A decrease very similar to the one found in normal subjects (P less than 0.05 vs. basal levels) was observed within 180 min from drug ingestion. Conversely, no significant changes were found after the same treatment in hyperprolactinemic patients with evidence of prolactinoma (seven females and one male). Taken together, these data seem to demonstrate that pharmacological enhancement of endogenous GABAergic tone is followed by inhibition of PRL secretion. They also suggest that GABA may exert an inhibitory control on PRL release in humans. In hyperprolactinemic subjects, this GABAergic control appears to be present only when a pituitary tumor cannot be demonstrated.

Dose-related effects of gamma-amino beta-hydroxy butyric acid (GABOB) infusion on growth hormone secretion in normal women

The effect of gamma-amino beta-hydroxy butyric acid (GABOB) infusion on GH secretion has been investigated in 3 groups of 6 normal women. Different doses (100 mg/min, 20 mg/min, 3.5 mg/min) of GABOB diluted with normal saline solution were infused iv over a 20 min period and compared with control tests performed using only saline solution. The infusions with GABOB at the doses of 100 mg/min and 20 mg/min were followed by a significant rise (p less than 0.01) in GH plasma levels, in comparison to control tests. The quantitative GH secretion after 100 mg/min GABOB infusion was significantly greater (p less than 0.05) in comparison with quantitative GH secretion after 20 mg/min GABOB infusion. After 3.5 mg/min infusion, only 3 out of 6 subjects showed an increase in the hormone concentrations. The acute injection with sulpiride (5 mg iv, bolus), performed either before or after the start of GABOB infusion, failed to affect GH response to GABOB. These results show that GABOB infusion induce a dose-dependent rise in GH plasma levels in normal women. The dopaminergic system does not seem to be involved in this effect.

Inhibitory effect of the dopamine agonist bromocriptine on the postcastration gonadotrophin rise in women

Basal or stimulated gonadotrophin plasma levels were measured after bilateral ovariectomy in untreated and bromocriptine (BCT)-treated normal women. BCT was orally administered from the 7th to the 14th day after ovariectomy at a dose of 3.75 mg/day. BCT significantly (P less than 0.05) inhibited LH release, both basally and after LRF stimulation. Plasma FSH levels were also reduced in treated subjects, but this decrease did not reach statistical significance relative to controls. The blunted postcastration gonadotrophin rise found with BCT administration suggests that pituitary gonadotropin secretion is, in part, under dopaminergic inhibitory control.

Norethisterone enanthate as an injectable contraceptive in puerperal and non-puerperal women

Norethisterone enanthate (NET-EN) was intramuscularly administered to 5 puerperal women and 20 non-puerperal women for a total of 366 months. Contraceptive effectiveness and side effects of the drug were evaluated. Basal levels of LH, FSH, prolactin (PRL), estradiol 17 beta (E2) and progesterone (P) were measured in blood samples collected from 5 non-puerperal women, while LH, FSH, PRL and norethisterone (NET) plasma levels were evaluated in puerperal women. NET was also assayed in plasma from breast-fed newborns. No woman became pregnant. Side effects consisted of only menstrual abnormalities. Ovulation (P plasma levels higher than 2000 pg/ml) was achieved in 3 patients during the first month of NET-EN treatment but luteal function appeared to be insufficient. In puerperal women, NET plasma levels showed a course similar to the one observed outside puerperium. Lactation was not inhibited, and NET transfer to newborn through milk was negligible, since NET was undetectable in newborn plasma when maximal levels were measured in the mother. It was concluded that NET-EN is an effective contraceptive drug, deprived of major side effects, and particularly useful in women affected by metabolic diseases or during puerperium.

Interference of dopamine infusion on gamma-amino butyric acid (GABA)-stimulated prolactin increase

The effects of simultaneous iv administration of dopamine (DA) and gamma-amino butyric acid (GABA) were evaluated in 5 normal women. After injection of 50 mg GABA alone, PRL plasma concentrations showed a significant (p less than 0.02) rise. DA infusion (500 g/min over a 60 min period) significantly (p less than 0.02) decreased PRL plasma levels. When GABA was administered intravenously during DA infusion, the rise of PRL plasma concentrations, which was observed after injection of GABA alone, was suppressed. PRL circulating levels significantly (p less than 0.02) decreased as during infusion with DA alone. These results seem to support the hypothesis that stimulatory effects of GABA or its analogues on in vivo PRL secretion could be due to an inhibitory effect of these drugs on endogenous DA.

Gamma-amino-beta-hydroxy butyric acid stimulates prolactin and growth hormone release in normal women

The influence of gamma-amino-beta-hydroxy butyric acid (GABOB) treatment on pituitary function has been investigated in this study. Different doses (50 x 100 mg) of GABOB were iv injected into three and six normal women, respectively. PRL and GH plasma levels were measured before and after the injection. The treatment with 150 mg GABOB, performed in another two normal women, was interrupted because of side-effects (loss of consciousness etc.) due to the treatment. The treatment with 50 mg GABOB did not induce significant variations of the two hormones; however, significant increases of PRL (P less than 0.05) and GH (P less than 0.01) plasma levels were observed after injection with 100 mg GABOB. The present data suggest that gamma-amino butyric acid (GABA) itself of GABAergic drugs might play an important role in the control of hypothalamic-pituitary function.