Fictive rhythmic motor patterns induced by NMDA in an in vitro brain stem-spinal cord preparation from an adult urodele

An in vitro brain stem-spinal cord preparation from an adult urodele (Pleur odeles waltl) was developed in which two fictive rhythmic motor patterns we re evoked by bath application of N-methyl-D-aspartate (NMDA; 2.5-10 mu M) w ith D-serine (10 mu M). Both motor patterns displayed left-right alternatio n. The first pattern was characterized by cycle periods ranging between 2.4 and 9.0 s (4.9 +/- 1.2 s, mean +/- SD) and a rostrocaudal propagation of t he activity in consecutive ventral roots. The second pattern displayed long er cycle periods (8.1-28.3 s; 14.2 +/- 3.6 s) with a caudorostral propagati on. The two patterns were inducible after a spinal transection at the first segment. Preliminary experiments on small pieces of spinal cord further su ggested that the ability for rhythm generation is distributed along the spi nal cord of this preparation. This study shows that the in vitro brain stem -spinal cord preparation from Pleurodeles waltl may be a useful model to st udy the mechanisms underlying the different axial motor patterns and the fl exibility of the neural networks involved.