Recycling of synaptic vesicles in motor nerve endings separated from their target muscle fibers.

The application of the myotoxic local anesthetic Carbocaine to the cutaneous-pectoris muscle of the frog produced muscle fiber degeneration. The degenerating muscle fibers were phagocytozed by macrophages leaving behind structurally intact motor nerve endings in close apposition to the sheath of basal lamina that normally surrounds muscle fibers. These target deprived nerve terminals retained their ability to recycle synaptic vesicles in that they showed a low basal rate of spontaneous uptake of HRP that increased several fold upon nerve stimulation.