OBJECTIVES: I. Physiology and Pharmacology of Neuromuscular Transmission (NMT) a. The effects of nerve crush at birth upon NMT in reinnervated muscles will be examined at 6-12 months after nerve crush at birth; b. The effects of neurally applied colchicine upon NMT will be examined; c. The effects of experimental hyperthyroidism upon NMT will be investigated. II. Action Potential Generating Mechanisms will be evaluated in single muscle fibers during reinnervation.