Abstract
Effects of Sch on responses of the trigeminal motoneuron induced by pressure applied to a restricted site on the masseter muscle were studied.
1. The optimal dose of Sch which effects the spontaneous discharges of the trigeminal motoneuron was about 0.8 mg/kg. The spontaneous discharge of the trigeminal motoneuron disappeared within 20 sec. after the injection of 0.8 mg/kg Sch and this silent phase continued for about 20 sec. After this stage the spontaneous discharge reappeared gradually and reached the maximum firing level at about 100 sec. after Sch in jection. At this stage the frequency of spontaneous firing was about 4 times greater than the control. This Sch effect continued for about 5min. However, a super optimal dose of Sch (1.2 mg/kg) induced grouped discharges of the motoneuron and the muscle showed local twitching.
2. The endplate of the extrafusal muscle fiber was more sensitive to Sch than that of the intrafusal muscle fiber.
3. It was confirmed that the pressure response of the trigeminal motoneuron originates from the deformation of the muscle spindle.
