Abstract
This study aimed to understand 1) how supraspinal locomotor driving signals are involved in generation of coordinated quadrupedal locomotion in rabbits, and 2) whether sensory feedbacks are necessary for such locomotor generation. For the first purpose, in decerebrate rabbits with a right hemisection of the upper cervical spinal cord, we observed locomotor movements of fore- and hind-limbs evoked by stimulation to the mesencephalic locomotor region (MLR). Stimulation to the left or right MLR evoked coordinated, rhythmic movements of fore- and hind-limbs on the left side but not on the right side. After additional hemisection of the left caudal medulla, MLR stimulation could no longer evoke any limb movements. For the second purpose, in decerebrate, paralyzed rabbits, we recorded electroneurograms (ENG) from extensor and flexor nerves of the hindlimbs during MLR stimulation. During the stimulation, bilateral hindlimb ENGs exhibited rhythmic activities, but nonalternating bursts of left and right ENGs were not always observed. These findings suggest that locomotor driving signals from the left or right MLR are mediated to both sides of the brainstem, and that the signals descending on one side of the spinal cord would activate central pattern generators (CPG) of fore- and hind-limbs on the same side, coordinately. In addition to the supraspinal signals, sensory feedback signals from active body parts during locomotion would be necessitated to coordinate activities of hindlimb CPGs on both sides. [J Physiol Sci. 2008;58 Suppl:S195]
