[Non-quantum release of acetylcholine from motor nerve endings and denervation changes in muscle fiber membranes in the rat following blockade of axonal transport].

On the 5th day after blockade of axonal transport with colchicine in rat the resting potential of diaphragm muscle fibre decreased, input resistance increased and the difference between postsynaptic and extrasynaptic membrane in this respect disappeared; extrasynaptic sensitivity to acetylcholine, anode breakdown and tetrodotoxin-resistant action potentials appeared almost in the same form as after nerve section. Application of colchicine to motor nerve, in contrast to nerve section, did not disrupt quantal and non-quantal acetylcholine secretion in motor nerve endings and did not stop muscle contractile activity. The size of non-quantal acetylcholine secretion was estimated by the amplitude of muscle membrane hyperpolarisation in the presence of curare in solution after preliminary acetylcholinesterase inhibition with armin. The data confirm the suggestion that the neurotrophic control of skeletal muscle fibre membrane in mammals is carried out by substances transported to muscle by axonal flow with participation of impulse activity. Synaptic acetylcholine secretion from motor nerve endings in non-quantal form does not play a marked role in neurotrophic control of muscle fibre membrane.