The effect of cholinergic manipulations on the analgesic response to cobrotoxin in mice.

Intracerebroventricular (i.c.v.) injection of cobrotoxin (CT), a neurotoxin isolated from the venom of Naja naja atra, produced an antinociceptive response in mice as measured by the tail-flick test. This effect of CT was blocked by systemic administration of atropine, but not by methylatropine or naloxone. Depletion of central acetylcholine (ACh) by hemicholinium-3 (HC-3) blocked the antinociceptive action of cobrotoxin. These results suggest that central cholinergic neurons are important for the mediation of the antinociceptive properties of cobrotoxin.