Acetylcholine synthesizing activity and nicotinic binding sites in rat hind limb muscles during reinnervation.

Acetylcholine synthesizing (ACh-s) activity and binding of the nicotinic ligands 3H-alpha-bungarotoxin (alpha-Btx) and 3H-d-tubocurarine (d-TC) were analysed in rat hind limb muscles for up to 6 months after a cryolesion of the sciatic nerve. Muscles of the contralateral leg served as controls. After cryolesion there was a rapid decrease in ACh-s activity parallel to a considerable increase in alpha-Btx binding. A clearcut increase in ACh-s activity was first seen at 32 days and complete restoration in ACh-s activity was seen from 2-3 months postoperatively. From the 16th day there was a rapid decrease in alpha-Btx bindings sites and initial values were seen at the 32nd day postoperatively. D-TC binding sites were relatively unchanged during the experimental period. The first neurophysiological signs of reinnervation were seen at 16 days. The rats were observed to move normally about 2 months postoperatively. Normalization of alpha-Btx binding sites seems to be an earlier sign of reinnervation than normalization of ACh-s activity.