Influence of muscarinic ligands on the amplitudes of the evoked surface potential's late components in the optic tectum of the urodele Plethodon jordani

Recordings of field potentials from the tectal surface of an urodele amphib ian were obtained in an in vitro preparation under influence of various mus carinic drugs. Bath applied acetylcholine (ACh) led to no change in the amp litudes or the shape of the evoked potentials. If the ACh-esterase blocker (-)-physostigmine was applied synchronously, the late components of the sur face potential increased in amplitude. The non-selective cholinergic agonis t carbachol showed a similar effect which was partially diminished by the n icotinic antagonist d-tubocurarine chloride (d-TC) and the muscarinic antag onist atropine sulfate. The application of the non selective muscarinic ago nist (+)-pilocarpine hydrochloride led to an increase of the late oligo- an d polysynaptic events. This effect was reduced by the M-1-antagonist pirenz epine dihydrochloride. The presented findings suggest that muscarinic recep tors play a more important role in tectal processing than assumed in previo us studies which emphasized the role of nicotinic receptors. (C) 2000 Elsev ier Science Ireland Ltd. All rights reserved.