ATROPINE INCREASES PILOCARPINE-INDUCED YAWNING BEHAVIOR IN PARADOXICAL SLEEP-DEPRIVED RATS

Paradoxical sleep (PS) deprivation has been suggested to induce supers ensitivity of postsynaptic dopamine (DA) receptors and subsensitivity of acetylcholine (ACh) receptors. Yawning behavior is reduced after PS deprivation and is believed to result from an interaction between ACh and DA systems. Concomitant treatment of PS deprived animals with DA agonists reverses PS deprivation effects on stereotypy and aggressiven ess. To examine this possibility on yawning behavior, rats were treate d, during the deprivation period, with atropine, methamphetamine, halo peridol or distilled water. Following PS deprivation, rats were inject ed with apomorphine or pilocarpine and number of yawns was recorded. A tropine increased yawning of PS deprived rats induced by pilocarpine, but not by apomorphine. Treatment with methamphetamine and haloperidol did not change PS deprivation effect on pilocarpine- and apomorphine- induced yawning. The data suggest that reversal of PS deprivation-indu ced yawning inhibition is mediated distinctly by both acetylcholine an d dopamine systems.