Muscarinic acetylcholine receptors on an identified motor neurone in the cockroach, Periplaneta americana

Muscarinic acetylcholine receptors (mAChRs) on the cell body of the fast coxal depressor motor neurone (Df) in the metathoracic ganglion of the cockroach Periplaneta americana were investigated using electrophysiological methods. Muscarinic agonists, arecoline and oxotremorine, induceddose-dependent depolarizations on motor neurone Df. McN-A-343, a vertebrate mAChR M1 subtype-selective agonist, failed to induce any responses when tested on the same neurone at concentrations of up to 1.0×10-4 M. The order of effectiveness of a series of muscarinic antagonists on the mAChRs od motor neurone Df is as follows: scopolamine > atropine > pirenzepine. 4-DAMP (1.0 × 10-5 M) had only a weak blocking effect and AF-DX 116 (1.0 × 10-5 M) was completely inactive. The pharmacological profile of muscarinic responses on motor neurone Df reveals a novel type of insect mAChR. © 1994.