[Reinnervation of a mixed muscle in the frog Rana temporaria with a regenerating homogeneous nerve].

Mixed muscle m. iliofibularis from the frog Rana temporaria, consisting of monosynaptically innervated phasic and polysynaptically innervated postural muscle fibers, was reinnervated by homogeneous tailor's nerve having no axons of tonic motor system in its composition. Within 2-7 months after nerves binding treatment phasic muscle fibers were easily identified by subneural apparatus structure revealed at coloration of synaptic acetylcholinesterase. Presynaptic part of neuromuscular apparatus of these fibers after the impregnation by protargol was presented by immature nervous terminals. The identification of tonic Muscular fibers was difficult especially at the late stages of reinnervation as subneural apparatus structure typical for tonic fibers was not revealed. Nonmyelinizated nerve fibers without features of terminal branch were observed in individual regions of nonidentified muscle fibers. The results obtained show that subneural apparatus of tonic muscle fibers depends to a great extent on the influence of inherent tonic motor system. Axons of phasic motor system even at distant reinnervation periods and in the absence of competitive influences of tonic motor system do not form typical "phasic" terminal picture of innervation under the contact with tonic muscle fibers.