[Does non-quantum secretion of acetylcholine from motor neuron endings participate in the neurotrophic control of the membrane potential of muscle fibers in the rat?].

The resting membrane potential of synaptic zone of muscle fibres within 2-3 mm (near) and 9-11 mm (far) of the nerve section of the rat diaphragm muscle was measured after 3 hours or on the 5th day after the motor nerve section. The membrane potential of "near" fibres was lower than that of "far" fibres. The presence of carbamylcholine or cGMP in the culture medium maintained the membrane potential of "near" fibres close to that of "far" fibres. Ouabain prevented these effects. On the 5th day after the nerve section the presence of carbamylcholine or cGMP had no effect on the membrane potential. In the in vitro experiments the nonquantal acetycholine release was equal in "near" and "far" fibres and just the same as in the control preparations. A conclusion is made that synaptic acetylcholine from motor nerve endings in nonquantal form does not play a significant role in neurotrophic control of the resting membrane potential of muscle fibres membrane in mammals.