The effect of 5-methoxytryptamine on golden hamster gonads is not a consequence of its acetylation into melatonin

Under experimental conditions, 5-MT had a physiological activity independent of that of melatonin, and induced total testicular regression and partial atrophy in golden hamsters kept under long photoperiod.

Abstract

Radioimmunoassay and high performance liquid chromatography were used to determine if the gonadal atrophy induced by late afternoon injections of 5-methoxytryptamine (5-MT) in golden hamsters kept under long photoperiod could be due to the acetylation of this compound into melatonin. An increase in plasma concentrations of melatonin (10-13 nmol/l) was detected 15 min after injection of 130 nmol 5-MT. An injection of 4.3 nmol melatonin generated a similar plasma concentration of melatonin. 5-MT (130 nmol) and melatonin (4.3 nmol) were then injected daily in the late afternoon to golden hamsters kept under long photoperiod. After 8 weeks, 5-MT induced total testicular regression, while melatonin induced partial atrophy only. Thus under these experimental conditions, 5-MT had a physiological activity independent of that of melatonin.