DOPAMINE-RECEPTORS MEDIATING YAWNING - ARE THEY AUTORECEPTORS

Yawning was induced in rats by the (+) enantiomer of 3PPP, while (-)-3PPP was inactive. Yawning was present 24, but not 1, 6 and 12 h after reserpine treatment. The (+)-3PPP-induced yawning was antagonized by haloperidol and sulpiride but not by domperidone. Reserpine-induced yawning was antagonized by sulpiride and by .alpha.-methyltyrosine suggesting that this behavior may be induced by endogenously released dopamine. Reserpine-pretreatment potentiated (+)-3PPP-induced yawning. The results argue against the view that yawning is the behavioral correlate of autoreceptor-mediated inhibition of DA transmission, and suggest that this behavior is due to the stimulation of a special population of central postsynaptic DA receptors.