piperidines and alpha-methyl-m-tyrosine

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 behavioural correlate of autoreceptor-mediated inhibition of DA transmission, and suggest that this behaviour is due to the stimulation of a special population of central postsynaptic DA receptors.

Topics: Animals; Domperidone; Drug Synergism; Haloperidol; Male; Methyltyrosines; Piperidines; Rats; Rats, Inbred Strains; Receptors, Dopamine; Reflex; Reserpine; Stereoisomerism; Sulpiride