Physiological properties of dissociated muscle fibres obtained from innervated and denervated adult rat muscle.

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Abstract
Adult rat flexor digitorum brevis muscles were dissociated by treament with collagenase and trituration. Several hundred isolated fibers were obtained from each muscle. Most isolated fibers appeared intact as judged by some morphological and physiological criteria, although resting membrane potentials were about -60 mV, which was somewhat lower than normal. A small percentage of the muscle fibers were branched. Acetylcholine [ACh] sensitivity was measured iontophoretically. The sensitivity fell abruptly outside the margin of the end-plate. Extrajunctional sensitivity was detected on all fibers and declined smoothly away from the end-plate to an undetectable level over a distance of about 200 .mu.m. On a few fibers, ACh sensitivity was mapped circumferentially from the end-plate. It appeared to decline with distance in a manner similar to the longitudinal sensitivity gradient. Fibers dissociated from muscles denervated a week earlier were sensitive to ACh everywhere on their surfaces.