PubMed Health⌕ Search

Biomedical subjects

G Delitala

Publications and source records attributed to G Delitala.

At least 91 records · Page 5Linked to original sources
PubMed1980

Two new dopamine agonists that are long acting in vivo but short acting in vitro.

The effects of two new ergolines, pergolide and CH29-717, on prolactin secretion in vitro and in vivo were compared with those of bromocriptine. Both ergolines had in vitro potencies similar to that of bromocriptine, but had a shorter duration of action. However, in vivo both were longer acting than bromocriptine after a single dose of 100 micrograms, and effectively suppressed prolactin secretion for greater than 24 h. It would appear that the pharmacokinetics of these ergolines are different to those of bromocriptine, and this may have considerable therapeutic importance.

Animals↗
PubMed1980

Metergoline and cyproheptadine suppress prolactin release by a non-5-hydroxytryptaminergic, non-dopaminergic mechanism.

A dispersed rat anterior pituitary cell system has been used to investigate the effects of cyproheptadine and metergoline on prolactin secretion. Both drugs were potent inhibitors of prolactin secretion. However, the inhibition was not antagonized by either 5-hydroxytryptamine or a variety of dopamine antagonists. We conclude that both drugs act through mechanisms that are neither 5-hydroxytryptaminergic nor dopaminergic.

Animals↗
PubMed1980

Chlorpromazine, haloperidol, metoclopramide and domperidone release prolactin through dopamine antagonism at low concentrations but paradoxically inhibit prolactin release at high concentrations.

1. The effects of chlorpromazine, haloperidol, metoclopramide and domperidone on the release of prolactin from perfused columns of dispersed rat anterior pituitary cells were studied. 2. Chlorpromazine, haloperidol, metoclopramide and domperidone antagonized the dopamine-mediated inhibition of prolactin release at low concentrations. 3. Each dopamine antagonist displaced the dose-response curve for dopamine-induced suppression of prolactin release to the right in a parallel manner. 4. At higher concentrations, the four drugs became less effective as dopamine antagonists. 5. At high concentrations in the absence of dopamine, chlorpromazine, haloperidol, metoclopramide and domperidone paradoxically suppressed prolactin secretion by an unknown mechanism.

Animals↗
PubMed1980

Domperidone, an extracerebral inhibitor of dopamine receptors, stimulates thyrotropin and prolactin release in man.

Domperidone, an extracerebral dopamine receptor antagonist, was given im to 12 normal subjects and to a group of patients with subclinical hypothyroidism to study its effect on PRL and TSH secretion. Domperidone induced in all subjects a quick and marked increment of serum PRL. At 180 min, the levels remained high. A small but significant increase of TSH was also observed in normal as well as in hypothyroid subjects. Since domperidone does not cross the blood-brain barrier, the hormonal changes observed may be mediated through the pituitary and median eminence, tissues which lie outside of the blood-brain barrier.

Adult↗
PubMed1980

Pituitary hormone secretion after inhibition of L-aromatic amino acid decarboxylase activity in man.

The effect of acute administration of 200 mg benserazide, an L-aromatic amino acid decarboxylase inhibitor, on pituitary hormone secretion in humans was studied. Benserazide induced in all subjects a quick and marked increment of serum prolactin (Prl) and TSH levels: at 180 min TSH and Prl levels were still significantly higher than the baseline values. Women with normal menstrual cycles showed a Prl response to benserazide which was significantly greater than that observed in post-menopausal women and men. In another experiment six normal men received 10 mg of domperidone, a peripheral dopamine receptor blocker. The hormonal changes induced by domperidone were comparable to those obtained with benserazide. Since domperidone and benserazide are thought not to cross the blood-brain barrier, these results suggest that dopamine regulates Prl and TSH secretion through extra blood-brain barrier structures.

Adult↗
PubMed1980

A comparison of the effects of four ergot derivatives on prolactin secretion by dispersed rat pituitary cells.

The inhibitory effects of dopamine and various ergot alkaloids on prolactin secretion were studied using continuously perfused columns of dispersed rat anterior pituitary cells. Bromocriptine (5 nmol/l) and lisuride hydrogen maleate (5 nmol/l) both inhibited prolactin secretion, the effects persisting for more than 3 h after the end of the administration of the drugs. A similar although less long-lasting effect was observed with lergotrile (50 nmol/l) and the new ergoline derivative, pergolide (5 nmol/l). These effects contrasted with the rapid disappearance of the action of dopamine. The potency estimates of the ergots relative to that of dopamine were: lergotrile, 2.3; bromocriptine, 13; lisuride, 15; pergolide, 23. Ther dopamine-receptor blocking drugs, metoclopramide and haloperidol, antagonized the prolactin release-inhibiting activity of the compounds; bromocriptine and lisuride showed the highest resistance to this dopaminergic blockade. The results suggested that the direct effect of the ergot derivatives on dispersed pituitary cells was mediated through dopamine receptors and emphasized the long-lasting action of bromocriptine and lisuride in vitro.

Animals↗
PubMed1979

Dynamic evaluation of prolactin secretion in patients with oligospermia: effects of treatment with metergoline.

Serum prolactin levels were measured in 50 patients with oligospermia and in 20 control subjects under fasting conditions and following the administration of levodopa, pyridoxine, metoclopramide, and synthetic thyrotropin-releasing hormone. Four patients (8%) under fasting conditions had prolactin levels slightly above the normal range. However, no significant differences in prolactin behavior were detected between patients with hyperprolactinemia, patients with normal prolactin levels, and control subjects. The four patients with hyperprolactinemia were treated with metergoline, an ergoline derivative. Metergoline administration promptly reduced the prolactin levels. Spermatogenesis was restored in three patients after 4 to 5 months of treatment.

Adult↗
PubMed1979

The effect of lisuride hydrogen maleate, an ergot derivative on anterior pituitary hormone secretion in man.

The effects of single oral doses of 0.2 mg of lisuride hydrogen maleate, a semisynthetic ergot derivative, on serum levels of prolactin (PRL), growth hormone (GH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), follicle stimulating hormone (FSH), cortisol and blood glucose were studied in six normal males. Lisuride effectively inhibited basal PRL secretion as well as the PRL response to TRH given 3 h later. In addition, the drug raised basal GH levels and decreased basal and TRH stimulated TSH secretion. No significant differences between lisuride and control were observed in basal LH and FSH, LHRH stimulated gonadotrophins or in cortisol. Drowsiness was noted by all subjects, one became nauseated and another vomited, 60 and 90 min respectively after administration of lisuride. No changes were seen in pulse rate and blood pressure. The endocrine effects of lisuride were attenuated by the prior administration of the dopamine antagonist metoclopramide. These results suggest that lisuride acts as a long-acting dopamine agonist and that therefore this drug could be of therapeutic use in hyperprolactinaemic states and acromegaly.

Adult↗
PubMed1979

Effects of the H2 receptor antagonist cimetidine on pituitary hormones in man.

The effects of the histamine (H2) receptor antagonist cimetidine on serum levels of prolactin (PRL), growth hormone (GH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), follicle stimulating hormone (FSH) and cortisol were studied in five normal males. Cimetidine, when given by infusion at the dose of 100 mg/h for 5 h, did not alter adenohypophyseal secretion either basally or after pituitary stimulation with LHRH and TRH. However, 400 mg cimetidine given intravenously as a bolus injection significantly stimulated PRL release in all subjects, without affecting any other measured hormone. A dose-reponse relationship existed, and 200 mg cimetidine seems to be the minimum PRL-releasing dose when given as an intravenous bolus injection. These results suggest that cimetidine releases PRL and that this effect is dose-related, but only when large intravenous injections are given.

Adult↗
PubMed1979

Piribedil inhibition of prolactin release induced by mechanical breast emptying in puerperal women.

The effects of a 5 day course of Piribedil, a dopaminergic agonist, on prolactin release evoked by mechanical breast emptying in puerperal women, was investigated. A daily dose of 75 mg. caused a significant decrease in the prolactin response to mechanical breast stimulation. Piribedil also proved clinically useful in inhibiting lactation. The role of dopaminergic mechanisms in the regulation of prolactin release induced by mechanical breast emptying are discussed.

Adult↗
PubMed1979

Effects of long-term treatment with metergoline in patients with idiopathic oligospermia.

The effect of metergoline, an ergoline derivative with antiserotonin as well as dopaminergic properties, was studied in forty-five male patients with idiopathic oligospermia. Metergoline treatment (6 mg daily for 5 months) had no demonstrable effect on spermatogenesis; moreover, it did not influence the serum levels of LH, FSH, testosterone and oestradiol although it significantly reduced prolactin levels. It is concluded that, in all likelihood, serotonin plays little or no part in the pathogenesis of idiopathic oligospermia and that pharmacological reduction of normal prolactin levels has no therapeutic effect on this disease.

Adult↗
PubMed1979

Enhancement of insulin-induced prolactin secretion by fluoxetine in man.

Fluoxetine hydrochloride, a specific inhibitor of serotonin reuptake, was given orally to five adult males to study its effect on fasting and insulin-stimulated release of PRL. A 3-day course of fluoxetine (30 mg daily) had no demonstrable effect on fasting PRL levels. Fluoxetine significantly enhanced insulin-induced PRL release. These data suggest that serotoninergic pathways have little or no part in the control of spontaneous PRL secretion in man, whereas they may play a role in insulin-stimulated PRL release.

Adult↗
PubMed1979

Effect of synthetic LH-RH and hCG administration on plasma testosterone, androstenedione, and estradiol 17beta levels in normal men and in patients with idiopathic oligospermia.

Plasma testosterone, androstenedione, and estradiol 17beta levels were measured in 20 normal men and in 20 patients with idiopathic oligospermia before and after iv hCG (5,000 IU) and synthetic LH-RH (50 microgram) administration. No statistically significant differences in the concentrations of the steroids examined were detected between patients and controls either under control conditions or under exogenous and endogenous gonadotropin stimulation.

Adult↗
PubMed1978

Hormonal and metabolic responses to an enkephalin analogue in normal man.

An enkephalin analogue [D-Ala2, MePhe4, Met(o)-ol] enkephalin (DAMME), given intravenously to normal subjects raised serum prolactin and growth-hormone levels but lowered serum levels of luteinising hormone, follicle-stimulating hormone, cortisol, and corticotrophin. There was also a small fall in total glucagon and gastric inhibitory peptide (G.I.P.) and a rise in thyrotrophin. beta-Lipotrophin, motilin, vasoactive intestinal peptide, insulin, gastrin, and pancreatic glucagon were unchanged. Blood-glycerol increased, and blood lactate, alanine, and glucose fell. Prior administration of the opiate antagonist, naloxone, attenuated the hormonal responses to DAMME. This enkephalin analogue produces endocrine and metabolic changes in man which may be mediated through opiate-binding receptors both within and outside the brain. The enkephalins and related substances may provide an important link between perception, behaviour, and neuroendocrine regulation of hormone secretion and metabolism.

Adrenocorticotropic Hormone↗