Influence of Membrane Receptor Lateral Diffusion on the Short-Term Depression of Acetylcholine-Induced Current in Helix Neurons.

Abstract

We have studied how various drugs increasing the rate of nicotinic acetylcholine receptors (nAChRs) lateral diffusion affect the depression of ACh-induced current in land snail Helix lucorum neurons responsible for defensive behavior. The acetylcholine (ACh) iontophoretic application protocol imitated the behavioral habituation protocol for the intact animal. We found that the drugs decreasing cholesterol level in cell membranes as methyl-β-cyclodextrin 1mM and Ro 48-8071 2µM, and polyclonal antibodies to actin-binding proteins as spectrin 5µg/ml and merlin 2.5µg/ml have changed the dynamic of ACh-current depression. The nAChRs lateral diffusion coefficient was obtained by fluorescence recovery after photobleaching. A curve fitting model specially created for analysis of short-term choline sensitivity depression in snail neurons helped us evaluate separately the contribution of nAChRs lateral diffusion, their endocytosis and exocytosis to observed effects during electrophysiological experiments. Taken together, we hypothesize that nAChRs lateral diffusion plays an important role in the cellular correlate of habituation in land snail Helix lucorum neurons.