Potential deflections at the terminal of the frog muscle spindle during stretch.

Dc-deflections were recorded with the paraffin gap method from the terminal of isolated single.type spindles in the frog sartorius muscle during ramp-and-hold stimulation. The amplitude of the dc-deflection over 60/lV was independent of the rate of afferent discharge and was little changed after inactivation of the axon terminal by irradiation with an ultraviolet light. The amplitude and the polarity of the dc-deflection could be altered with currents passing across the gap. A change in the longitudinal resistance of the axon in association with its lateral movement during stretch of the spindle may evoke a part of the dc-deflection by dividing a steady potential, although the dc-def1ection below 60 /lV in amplitude may be a genuine generator potential.