Alpha-2 adrenoceptor mediated paradoxical (REM) sleep inhibition in the cat

USING in vivo microdialysis infusion, we have studied the adrenoceptor subtypes implicated in paradoxical sleep (PS) generation in the cat. Both epinephrine and norepinephrine inhibited PS and induced PS without atonia when applied to the caudal peri-locus coeruleus-alpha (peri-LC alpha) of the mediodorsal pontine tegmentum. This effect was mimicked by clonidine, an alpha(2)-selective adrenoceptor agonist, while alpha(1) and beta agonists were ineffective. The norepinephrine effect was antagonized by co-application of the alpha(2)-selective antagonists, rauwolscine or RX 821002, but not by alpha(1) or beta(1) antagonists. In addition, clonidine completely blocked the PS-inducing effect of carbachol, applied to the peri-LC alpha. The present data indicate that alpha(2) adrenoceptors located in the caudal peri-LC alpha play a critical role in inhibitory mechanisms of PS generation. NeuroReport 10:2199-2204 (C) 1999 Lippincott Williams & Wilkins.