[The characteristics of the impulse activity of the motor units of the muscles in the pelvic floor in the cat].

The investigation have been designed to elucidate the background and thermoregulatory activity (TA) of the motor units (MUs) of pelvic floor muscles (m. spincter ani externus, m. levator ani) and hind limb muscle (m. sartorius) in cats under anesthesia. The MUs of m. sphincter ani externus presented two patterns of background activity--the stationary and the rythmical ones. M. levator ani and m. sartorius presented no activity at room conditions (+22 degrees C). General cooling evoked TA in all the investigated muscles. The discharge frequencies of pelvic floor MUs (4-8 imp/s) during TA were shown to overlap with those of hind limb, muscles (5-9 imp/s). The correlation of MUs bioelectrical characteristics with histochemical and contractile properties of m. sphincter ani externus as fast-twitch muscle is discussed. The possible mechanisms responseble for MUs control in skeletal muscles with different specialization in modulated thermoreceptory afferent input are proposed.