Physiological regulation of G4 AChe in fast-twitch muscle: effects of exercise and CGRP

This work addresses the physiological regulation of the tetrameric (G4) form of acetylcholinesterase (AChe) in end-plate regions of anterior gracilis muscles from adult male Sprague-Dawley rats subjected to short-term low-intensity treadmill exercise. Experiments involved analyses of muscle AChe molecular form activities, endogenous calcitonin gene-related peptide (CGRP) levels, and the effect of exogenous CGRP on AChe forms after exercise. Animals were exercised twice per day for 1 or 2 days. Daily training sessions of 135 min (10 min of walking alternating with 5 min of resting) were separated by a 105-min resting period. Results show that exercise causes a slight decline in endogenous CGRP and a selective increase in G4 AChe that is partially reversed by treatment with exogenous CGRP. These findings indicate that CGRP influences the mechanism(s) by which G4 AChe in intact fast-twitch anterior gracilis muscles adapts to enhanced motor activity. They are also consistent with the hypothesis that, in addition to acetylcholine, neurogenic CGRP participates in the regulation of G4 AChe at the neuromuscular junction.