The presynaptic active zones in three different types of fibres in frog muscle.
Presynaptic active zones were studied in slow, fast and intermediate types of frog muscle fibres in freeze-fracture replicas. In fast fibres, the double rows of paired particles are present on active zone ridges perperdicular to the longitudinal axis of the nerve whereas in slow fibres active zone ridges are rudimentary or absent and double rows of particles occur in all directions, mostly paired, sometimes single. In the intermediate type of muscle fibres both types of active zone deployment coexist on a single muscle fibre.
D000818:Animals; D005614:Freeze Fracturing; D009132:Muscles / Q000294:innervation; D009411:Nerve Endings / Q000648:ultrastructure*; D009469:Neuromuscular Junction / Q000648:ultrastructure*; D011894:Rana pipiens; D013570:Synaptic Membranes / Q000648:ultrastructure*