Muscarinic M1 and M2 receptors, fasting and seizure development in animals

Muscarinic M-1 and M-2 receptors are widely distributed in the brain and contribute to various physiological and pathological functions. It is well known that enhancement of cholinergic activity produces convulsions in animals. Pilocarpine, the M-1 muscarinic receptor agonist, is commonly used to induce seizures in rodents. On the other hand it has been reported that fasted rats and mice pretreated with the M-1 and M-2 receptor antagonist atropine, scopolamine or biperiden develop convulsions after food intake indicating cholinergic hypoactivity as the underlying mechanism. This review will present pharmacological data for the M-1 and M-2 receptors in the brain and focus on the contrasting findings related to their contribution to convulsions.