[Decrease in the frequency of muscle spindle discharges during muscle stretching].

When studying responses of 500 muscle receptors to stretching of the m. triceps of the cat deafferented hindlimb, 23 cases revealed a transient decrease in the firing rate (DFR) of muscle spindles' receptors. The DFR occurs in the same receptor at different forms and rates of stretching approximately at the same area of stretching ("the DFR area"). When increasing the rate of stretching, the DFR effect is enhanced. The DFR effect seems to be due to a short-lasting unloading of the spindle area which contains the receptor terminals. The unhomogenous structure of the extrafusal muscle as well as various mechanical properties of the intrafusal muscle fibers can provide necessary conditions for the above effect.