Testosterone-induced changes of choline acetyl-transferase and cholinesterase activities in rat levator ani muscle.

One year after castration the activities of choline acetyltransferase (ChAc) and of cholinesterase (ChE) in the levator ani (LA) muscle of male rats were lowered by 42 and 79% respectively. The weight of the muscle corresponded to 15% of control values. These changes were not accompanied by a decrease in the number of the muscle fibres. Treatment with testosterone rapidly increased the activity of ChAc and the weight of the muscle near to control values; the restoration of ChE was less complete. Testosterone produced an increase in the size of the muscle fibres and increased the histochemically observed activity of ChE in the postsynaptic part of the motor end-plates. In non-castrated rats the administration of testosterone increased the weight ofthe LA muscle, but was not accompanied by an increase of ChAc above control values.