ATTENUATION OF CHOLINERGIC ANALGESIA BY NIFEDIPINE

Nociception was tested in mice receiving oxotremorine or physostigmine either after the dihydropyridine calcium channel blocker nifedipine o r the non-calcium antagonist vasodilator hydralazine. Nifedipine did n ot change the reaction time to thermal stimulation (tail-flick test), but attenuated the prolonging action on tail-flick latencies exerted b y the two cholinomimetic agents. Hydralazine had no effect alone nor m odified the action of cholinomimetics. The results suggest that attenu ation of cholinergic analgesia by nifedipine might be related to not y et defined neuronal changes produced by calcium channel blockade, but changes in the pharmacokinetics of oxotremorine and physostigmine cann ot be ruled out.