NMDA RECEPTOR-MEDIATED OSCILLATORY ACTIVITY IN THE NEONATAL RAT SPINAL-CORD IS SEROTONIN DEPENDENT

The effect of serotonin (5-HT) receptor blockade on rhythmic network a ctivity and on N-methyl-D-aspartate (NMDA) receptor-induced membrane v oltage oscillations was examined using an in vitro neonatal rat spinal cord preparation. Pharmacologically induced rhythmic hindlimb activit y, monitored via flexor and extensor electroneurograms or ventral root recordings, was abolished by 5-HT receptor antagonists. Intrinsic mot oneuronal voltage oscillations, induced by NMDA in the presence of tet rodotoxin (TTX), either were abolished completely or transformed to lo nglasting voltage shifts by 5-HT receptor antagonists. Conversely, 5-H T application facilitated the expression of NMDA-receptor-mediated rhy thmic voltage oscillations. The results suggest that an interplay betw een 5-HT and NMDA receptor actions may be critical for the production of rhythmic motor behavior in the mammalian spinal cord, both at the n etwork and single cell level.