Effect of the cholinesterase-inhibiting substance galanthamine on evoked visual potentials in rats

We studied the effect of intravenous injection of the cholinesterase inhibitor galanthamine (GAL) in doses from 0.025 to 5.0 mg/kg on electrically evoked field potentials in rat visual cortex. In all the experiments the amplitude of late components of evoked potentials was significantly reduced, while early components remained unaffected. These findings indicate that cortical cells are inhibited by acetylcholine (ACh). Furthermore, combined application of a muscarinic receptor blocker (atropine) and GAL reliably suppressed the effects of galanthamine. These observations suggest that ACh-induced inhibition may be mediated by activation of GABAergic interneurones that possess muscarinic receptors.