A dose-response study examining the effects of ritanserin on human slow wave sleep.

This study investigated the effects of placebo, 1 mg, 3 mg, 10 mg and 30 mg ritanserin and 10 mg diazepam on human sleep. Twelve normal volunteers participated in this randomized, double-blind, placebo-controlled cross-over sleep study. A clear dose-response relationship was found for ritanserin with higher doses evoking increased duration of slow wave sleep.

The effects of chronic ritanserin treatment on sleep and the neuroendocrine response to L-tryptophan.

A previous study has shown that acute administration of the 5-HT2 receptor antagonist ritanserin doubles Slow Wave Sleep (SWS) and increases the prolactin (PRL) response to L-tryptophan (LTP). The present study investigated the effect of repeated ritanserin treatment on sleep, neuroendocrine response to LTP and 5-HT2 platelet receptor binding. After 2 weeks, ritanserin administration SWS was persistently increased but the PRL response to LTP was unchanged. Platelet 5-HT receptor binding was undetectable at the end of ritanserin treatment but recovered 2 weeks after drug withdrawal. The results suggest that ritanserin causes a sustained effect on the 5-HT mechanisms mediating SWS and on platelet 5-HT2 receptors. However, adaptation occurs to its effect on 5-HT-mediated neuroendocrine responses.

5-Hydroxytryptamine-2 antagonist increases human slow wave sleep.

Ritanserin, a specific 5-HT2 antagonist, was given to volunteers in a double-blind placebo controlled sleep study. Slow wave sleep doubled in duration at the expense of stage 2. The finding that a serotonin antagonist changed the architecture of sleep without producing insomnia is of fundamental importance and calls for a re-examination of traditional theories of sleep control which assign a facilitatory role to serotonin.

The endocrinology of stress.

With the advance in hormone assay techniques it has been demonstrated that stress may be characterised by a number of endocrinological changes which are not limited solely to the secretion of catecholamines and adrenal steroids. This article reviews the effects of various stressors on these and other hormones. Aviation is a source of a wide range of stressors including radial acceleration (+Gz) Since its magnitude and duration may be controlled experimentally by using the human centrifuge, it is possible to quantify such a stressor when investigating endocrinological markers of stress. Sustained +Gz acceleration results in a "dose-dependent" secretion of cortisol, i.e. the higher the acceleration, the greater the cortisol secretion. In addition, increases in the concentrations of arginine vasopressin and catecholamines occur but these are not accompanied by changes in prolactin or growth hormone.

Continuous infusion anaesthesia in baboons with alphaxolone-alphadolone.

39 experiments were carried out in baboons using continuous intravenous infusion of alphaxalone-alphadolone as an anaesthetic for periods of up to 6 h. This steroid anaesthetic was found to be safe and reliable, with smooth, rapid induction, uneventful recovery, and no evidence of cumulative effect.