Time course of proteolytic enzyme alterations in the motor end-plates after stimulation.

Authors studied the proteolytic enzyme activity of motor end plates in the diaphragms and M. flexor digitorum brevis of rats after administration of cholinesterase inhibitors and after supramaximal electric stimulation, using the colour film digestion technique. Enhanced enzyme activity characterizing stimulated motor end plates persisted up to 12 h after stimulation. No proteolytic activity could be shown any more 24 h after stimulation, indicating restoration of the resting state. The role of metabolites (oligopeptides and amino-acids) released by the function-dependent axoterminal proteolysis is discussed in relation to neurochemical transmission processes.