Figure 9.

Activation of sacral VF neurons and the thoracolumbar CPGs depends on non-NMDA receptor-mediated synaptic transmission in the sacrocaudal segments of the cord. A, The activity of sacral VF neurons during stimulation of the Co1 dorsal root is shown with the motor output recorded from the left and right S2 and L2 ventral roots, before (Control) and 12 min after (Rostral CNQX) addition of the non-NMDA receptor antagonist CNQX (10 μm) to the thoracolumbar compartments of a dual-chamber experimental bath. Stimulus train: 40-pulse 2.5 Hz at 12 μA. B, In a different experiment, similar recordings (as in A) were done before (Control) and 8 min after (Caudal CNQX) bath application of CNQX to the sacrocaudal compartment. Stimulus train: 50-pulse 2.5 Hz at 10 μA. Note the acceleration of the sacral rhythm and the oscillatory drive of the VF neurons as the lumbar rhythm was blocked (A), and the total elimination of the activity of VF neurons, the sacral and lumbar activity when the sacral segments were exposed to CNQX (B). A, B, The neurons are right-S2 neurons back-labeled from the contralateral VF at the lumbosacral junction.