Influence of Organophosphate and Anticholinergic Agents on CA++ -Dependent Processes in Synaptic Transmission

The present report reviews progress over a period of 28 months in studies concerning the effects of organophosphates and anticholinergic agents on Ca++ -dependent processes in synaptic transmission. Processes which were studied include voltage-dependent and receptor operated Ca++ channels, Na+/Ca++ exchange, Ca++/Mg++ -ATPase plasma membrane pump, and ATP-dependent Ca++ uptake into endoplasmic reticulum. Initial studies focused on the effect of muscarinic receptor agonists on voltage-dependent Ca++ channels, Ca++/Mg++ -ATPase, ATP-dependent Ca++ uptake, and Na/Ca++ exchange in rat brain synaptosomes and synaptosomal membranes. These studies characterized two phases of Ca++ influx and time courses for Ca++ entry. Acute in vitro soman treatment (50 microns for 2 min) did not alter Ca++ influx through voltage-operated channels. Keywords: Acetylcholine; Organophosphates; Calcium transport; Synaptosome; Pharmacology. (JES)