THE FIRING PATTERN OF THE LOCUST (SCHISTOCERCA-GREGARIA AMERICANA) MESOTHORACIC FEMORAL MOTOR AXONS IN RESISTANCE REFLEXES AND DURING WALKING ON A TREADMILL

The firing pattern of the locust mesothoracid femoral motoneurones during passive extension of the tibia (resistance reflexes) has been examined. Of the flexor excitors, some are activated only by very fast tibial movements producing a few spikes. Others produce a discharge which lasts as long as the imposed tibial extension. The flexor slow motoneurones are the only spontaneously active neurones and their frequency increases and remains high as long as the tibial extension lasts. The inhibitors remain silent during active tibial flexion (or extension) and they are active only during maintained extension. From the mesothoracic extensor tibiae motor axons, the slow extensor tibiae fires during tibial flexion and the inhibitor during tibial extension. The fast extensor tibiae is silent during tibial movement. The activity of the femoral motoneurones was also studied in a tethered locust walking on a treadmill. First, the similarities in the firing motor pattern between a deafferented and a normal walking leg were established and then the activity of the flexor tibiae motoneurones, recorded from a deafferented leg of a walking locust, was analysed. A modification in the resistance reflexes during the active stage of the animal was also demonstrated. The resistance reflexes seemed to become assistant reflexes during walking. © 1990.