The local anesthetic lidocaine suppresses different pain conditions when administered systemically. Part of the antinociceptive effect appears to be mediated via receptor mechanisms. We have previously shown that muscarinic and nicotinic agonists that produce antinociception increase the intraspinal release of acetylcholine. In the present study it was hypothesized that systemically administered lidocaine is acting through the same mechanisms as cholinergic agonists and affects the intraspinal release of acetylcholine. Microdialysis probes were placed in anesthetized rats for sampling of acetylcholine. Ten and 30 mg/kg lidocaine injected intravenously significantly increased the intraspinal release of acetylcholine. The effect of lidocaine could be reduced by pretreatment with intraspinally administered atropine or mecamylamine. Our results suggest that the antinociceptive effect produced by systemically administered lidocaine is mediated through an action on muscarinic and nicotinic receptors.