The proposed research is intended to probe the function(s) of acetylcholine (ACh) in the large parasitic Ascaris lumbricoides. Studies to date have concentrated on a detailed localization of the enzymes for ACh synthesis (choline acetyltransferase-CAT) and degradation (acetylcholinesterase-AChE). CAT is restricted to ectodermal cells but is not restricted to neurons. AChE is found in all tissues but in widely divergent amounts. Both enzymes have been found to exist in separable forms. Current work is aimed at localizing separable forms of CAT and AChE and comparing their properties in order to determine whether they represent the same or different enzymes. Experiments to analyze the localization of ACh itself and ACh receptors are also proposed.