Development of hindlimb locomotor activity in the bullfrog (Rana catesbeiana) studied in vitro.

The isolated central nervous system of the bullfrog larva (tadpole) is a valuable model system for studying the development of central motor control because the neural activity for locomotion is expressed in vitro. Patterned synaptic activation of immature hindlimb motoneurons is present before the bones and muscles of the hindlimb differentiate, and it develops against the background of the tadpole's functionally mature motor program for tail oscillations. This activation of hindlimb motoneurons later produces patterned bursting that underlies coordinated stepping and frog kicks.