Histochemical specificity of cholinesterases to phenylthioacetate in differentiated neural tissues of insects and teleosts.

Housefly brain cholinesterase was histochemically demonstrated to hydrolyse phenylthioacetate at a very high rate, similar in distribution to that previously reported for acetylthiocholine. However, teleost neural retina cholinesterase would not hydrolyse the aromatic substrate, but the enzyme did cleave acetylthiocholine. Paraoxon and eserine were utilized to show selective patterns of inhibition in the two tissues. This high degree of substrate selectivity is discussed in conjunction with the possible development of selective insecticides.