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Biomedical subjects

J C Little

Publications and source records attributed to J C Little.

11 recordsLinked to original sources
PubMed1978

Effects of melatonin and natural and synthetic analogues of arginine vasotocin on plasma prolactin levels in adult male rats.

A significant elevation in plasma prolactin was observed 10 min following the intravenous injection of 100 microgram of melatonin into either estrogen-progesterone (EP) primed or into nonsteroid-treated male rats. 60 min postinjection in the EP primed rat, the groups treated with 100 microgram or 10 mg of melatonin had signficantly elevated plasma prolactin levels while no effect was observed with these same doses in the nonsteroid-treated rats. Compared to diluent-treated controls, a significant elevation in plasma prolactin was observed at 10, 20 and 60 min following the intravenous injection of either 1 microgram arginine vasotocin (AVT) or 1 mg melatonin into EP primed male rats. A consistent rise in plasma prolactin was also evident after the injection of 1 microgram of either arginine vasopressin, lysine vasopressin or AVT. Oxytocin had no effect on plasma prolactin values. The intravenous administration of 1 microgram of (deamino-1,6 dicarba, 8-arginine)-vasotocin caused a significant elevation of plasma prolactin 10 and 20 min after injection. However, the injection of another analogue of AVT, (4-leucine, 8-arginine)-vasotocin, had no effect on prolactin release at the time points measured.

Animals↗
PubMed1977

Subcutaneous melatonin implants inhibit reproductive atrophy in male hamsters induced by daily melatonin injections.

Daily afternoon (at 7 p.m.) injections of melatonin (25 microng in oil) into adult male hamsters for 50 days led to atrophy of the testes and accessory sex organs (seminal vesicles and coagulating glands) and in a significant depression in pituitary LH and prolactin content and concentration. These actions of melatonin were prevented if the animals had been pinealectomized before the daily melatonin injections were begun. Likewise, if hamsters received a weekly subcutaneous implant of melatonin in beeswax (1 mg melatonin in 24 mg beeswax) the daily melatonin injections failed to inhibit the growth of the reproductive organs and to depress pituitary LH and prolactin levels. Beeswax by itself had no such effect.

Animals↗
PubMed1977

A clinical comparison of nomifensine and amitriptyline.

1. The study consists of a double-blind evaluation of nomifensine and amitriptyline in a group of 37 patients with primary depressive illness. 2. The patients were referred by their family doctors on the basis that they would ordinarily have been prescribed a tricyclic antidepressant drug. Random allocation to the treatment groups took place. Assessment took place at weekly intervals over a 4-week period using the Visual Analogue Scale for depression and anxiety, and a side-effects check-list. Patients were also assessed on the Hamilton Depression Scale before the onset and at the end of the trial. 3. No significant difference was found between the two groups as regards relief from depression and anxiety, although marginal differences were found in favour of the amitriptyline group. 4. The overall frequency of side-effects was similar in the nomifensine and amitriptyline patients, But the development of severe side-effects was significantly more common in the amitriptyline group.

Adjustment Disorders↗
PubMed1977

Stimulation of rat prolactin secretion in vivo by arginine vasotocin: influence of age of solution, nighttime administration, and dose.

In male rats pretreated for 3 days with 50 microgram of estradiol benzoate (E) and 25 mg of progesterone (P), the i.v. administration of 1 microgram of arginine vasotocin (AVT) from solutions that were 0, 6, 24 or 48 h old caused a significant rise in plasma prolactin (Prl) 10 min after injection. In the 2nd experiment, the i.v. injection of 1 microgram AVT into EP-primed adult male rats at either 01:00 (during darkness) or 13:00 h (during light) resulted in a significant and similar elevation in plasma Prl levels. In the 3rd experiment, normal adult male rats under urethane anaesthesia were given an i.v. injection of diluent or of 100 ng, 1 microgram or 10 microgram AVT. A significant rise in plasma Prl was observed at 10 and 20 min following injection only in the group treated with 1 microgram AVT. In none of these experiments did AVT alter the content of pituitary Prl.

Animals↗
PubMed1977

The effects of pineal indoles given late in the light period on reproductive organs and pituitary prolactin levels in male golden hamsters.

Intact and pinealectomized adult male hamsters kept in light:dark cycles of 14:10 (in hours) were given daily injections of either 25 microgram melatonin, 5-methoxytryptophol, N-acetylserotonin, or 6-hydroxymelatonin at 19.00 hours (13h after lights on). The injections were continued for 50 consecutive days. The daily melatonin injections significantly elevated body weights and depressed the growth of the testes and accessory sex organs and pituitary prolactin levels in intact hamsters. By comparison, in pinealectomized animals daily afternoon melatonin injections failed to alter body or testicular weights or pituitary prolactin levels. These findings indicate that for single injections of melatonin to be antigonadotrophic in the male hamster, the pineal must be intact. In intact animals, 5-methoxytryptophol and N-acetylserotonin slightly depressed the growth of the reproductive organs and pituitary prolactin levels, respectively. Again, these effects were negated by removal of the pineal gland. 6-Hydroxymelatonin was without influence on any of the parameters of reproduction that were measured.

Animals↗