Kinetics of expression of ACh receptor alpha-subunit mRNA in denervated and stimulated muscle.

Levels of the acetylcholine receptor (AChR) alpha-subunit mRNA were quantified in chick leg muscle, both after section of the sciatic nerve and following electrical stimulation of the denervated leg musculature. Whereas a lag period of approximately 17 h intervenes between the nerve section and the increase in message level, electrical stimulation leads to an immediate decline, which proceeds with a half-life of 3-4 h, similar to the decay induced by treatment with actinomycin D. The asymmetry in the kinetics of activation and repression can be accommodated by several regulatory schemes of which the simplest contains an autocatalytic loop as recently proposed by Changeux (The New Biologist 3: 413-429, 1991).