Comparison of stimulation and insulin effects on denervated mouse soleus muscles

A comparison has been made between the responses of denervated mouse soleus muscles to direct electrical stimulation, as reported by earlier workers, and to incubation with supraphysiological concentrations of insulin. The parameters of interest were resting membrane potential (RMP), qualities of the active state, the amount of alpha bungarotoxin (BUTX) binding, and chemosensitivity, as measured by the strength of acetylcholine (ACh)-induced contractures. In all aspects, the changes recorded after insulin, were in the same direction as with direct stimulation, however, owing to the time limitations of in vitro testing, were smaller. It is suggested that the effects of electric shocks on denervated muscles are the result of activation of the insulin receptor, or some similar macromolecule, which appears to be sensitive to the membrane potential. The possible interrelations between acetylcholine and insulin receptors in neurotrophic control are discussed.