Induction of alternating bursting activity in the spinal cord of functionally-mature mouse. A: The activity of the ventral roots at the lower lumbar (L6) and mid-sacral (S2) segments on the left (L) and right (R) sides of a spinal cord obtained from a mouse at P11. The application of serotonin (5-HT), dopamine (DA), and NMDA induces low-amplitude, left-right alternating, rhythmic bursting at the sacral, but not the lumbar, segments. B: Recordings from a P12 mouse showing the effect of the same concentrations of serotonin, dopamine, and NMDA. Only the left side ventral root at L6 is showing low amplitude bursts (arrows), while the right side and sacral roots are silent.