Abstract
We reported that when rats with the vermis ablated partially were dropped from the supine position, body turning of air righting were either too less (undershooting) or too much (overshooting). Reduction of vermal inhibition by ablation could facilitate fastigial neurons. Present study investigated if fastigial nucleus stimulation could provide similar effects on air righting movements as the vermal ablation. Under Nembutal anesthesia, wire electrodes were inserted into the fastigial nuclei on both sides and fixed on the skull with dental resin in male, adult Wistar rats. After recovery from the operation the rats were dropped from the supine position, while electrical stimulation was applied. Stimuli, currents 200-400mA, pulse widths 200-300msec., repetition frequencies 33-100Hz, duration 2 seconds were started just prior to and ended after falling. When the animals stood still on the four limbs, the stimulation with such parameters induced tilt of the whole body toward the stimulated side. Effects on the air righting were as follows; righting movements began earlier, the head and the body turned toward the stimulated side, and the ventriflexion of the body preceding the body turning in normal righting occurred simultaneously with the turning, and the body turnings varied in degree from under- to overshooting. Further, the landing posture of normal righting, in which the four limbs were extended and the head was raised, was abolished; the four limbs were rather flexed after the body turning. These results were similar to those of vermal ablation. [Jpn J Physiol 54 Suppl:S183 (2004)]
