EFFECTS OF 5HT(3) RECEPTOR ANTAGONISM BY TROPISETRON ON THE SLEEP EEGAND ON NOCTURNAL HORMONE-SECRETION

Two dosages (5 mg and 25 mg) of the selective 5HT(3) receptor antagoni st tropisetron (ICS 205-930) were administered to healthy male control s, and the effects on the sleep EEG and nocturnal secretory activity o f growth hormone (GH) and cortisol were evaluated. The lower dosage wa s administered to four subjects and the higher dosage to eight on 5 co nsecutive days, preceded and followed by 2 days of placebo treatment. After 25 mg of tropisetron, there was a slight increase in REM sleep i n the first part of the sleep period, and stage 2 was decreased during the total night. In addition, plasma cortisol levels increased earlie r than under placebo, and plasma GH levels were reduced in the second part of the night. Thus, only discrete effects of tropisetron upon sle ep-endocrine activity were noted, making it unlikely that serotoninerg ic neurotransmission exerts ifs well-documented effects upon sleep thr ough 5HT(3) receptors.