REM sleep induction in prepubertal boys by vasotocin: evidence for the involvement of serotonin containing neurons.

The pineal nonapeptide hormone arginine vasotocin (AVT) (100 ng/kg) administered intra-nasally (IN) to healthy prepubertal boys, dramatically increased the amount of REM sleep, decreased REM sleep latency, and induced REM periods at sleep onset. Neither arginine vasopressin (AVP) nor oxytocin administered IN at the dose of 100 ng/kg was able to reproduce the effects of AVT, demonstrating its high specificity. Methergoline, a selective central 5-hydroxytryptamine (5-HT) receptor blocker, administered IN at the dose of 100 ng/kg, completely prevented AVT induction of REM sleep. Fluoxetine, a specific 5-HT uptake inhibitor, administered IN at the dose of 25 microgram/kg, 10 min after AVT, greatly potentiated the effects of AVT in inducing REM periods at sleep onset and in increasing the amount of REM sleep and the percentage of dream reports. It is suggested that AVT induces REM sleep in prepubertal boys by interfering with 5-HT neurotransmission and that the high sensitivity of prepubertal boys to AVT reflects an immaturity of REM triggering centers.