Effects of Motor Inactivation on the Chemical Sensitivity of Skeletal Muscle

Abstract

Abstract J ohns T. R. and S. T hesleff . Effects of motor inactivation on the chemical sensitivity of skeletal muscle. In order to determine whether the lack of motor nerve impulses, without denervation per se , alters the chemically sensitive area in skeletal muscle, the size of the ACh‐sensitive areas in muscle fibres of cat tenuissimus were measured after isolation of the motor neurones by severance of the dorsal roots below a lower lumbar cord transection. The sensitivity of the individual muscle fibre to ACh was determined by iontophoretic micro‐application of the drug, and by intracellular recording of the potential change. The frequency of miniature end‐plate potentials, their amplitude, and their time course, were relatively unaffected by the isolation procedure. The procedure also caused little increase in the size of the ACh‐sensitive surface. Therefore, inactivation per se did not alter the chemically sensitive area.