RAPID COMMUNICATION NMDA Receptor-Mediated Oscillatory Activity in the Neonatal Rat Spinal Cord Is Serotonin Dependent

MacLean, Jason N., Kristine C. Cowley, and Brian J. Schmidt. spinal cats reverses perturbations of the locomotor pattern NMDA receptor-mediated oscillatory activity in the neonatal rat produced by 5-HT agonists (Barbeau and Rossignol 1990), spinal cord is serotonin dependent. J. Neurophysiol. 79: 2804– it remains to be shown whether endogenous 5-HT receptor 2808, 1998. The effect of serotonin (5-HT) receptor blockade on activation is critical for network rhythmogenesis in the mamrhythmic network activity and on N-methyl-D-aspartate (NMDA) malian spinal cord. In the lamprey, application of 5-HT dereceptor-induced membrane voltage oscillations was examined uscreases swimming frequency (Harris-Warrick and Cohen ing an in vitro neonatal rat spinal cord preparation. Pharmacologi1985) and slows the repolarizing phase of NMDA receptorcally induced rhythmic hindlimb activity, monitored via flexor and mediated intrinsic voltage oscillations in spinal neurons extensor electroneurograms or ventral root recordings, was abol(Wallen et al. 1989). In contrast, 5-HT is required for the ished by 5-HT receptor antagonists. Intrinsic motoneuronal voltage oscillations, induced by NMDA in the presence of tetrodotoxin maturation of locomotor rhythms (Sillar et al. 1995) and (TTX), either were abolished completely or transformed to longthe expression of intrinsic voltage oscillations (Scrymgeourlasting voltage shifts by 5-HT receptor antagonists. Conversely, Wedderburn et al. 1997; Sillar and Simmers 1994) in am5-HT application facilitated the expression of NMDA-receptor– phibian spinal neurons. The present study examines whether mediated rhythmic voltage oscillations. The results suggest that an 5-HT is essential for network rhythmogenesis and/or moduinterplay between 5-HT and NMDA receptor actions may be critilation of NMDA-mediated oscillatory activity in the mamcal for the production of rhythmic motor behavior in the mammamalian spinal cord. lian spinal cord, both at the network and single cell level. Some of the following data has been presented previously in abstract form (MacLean and Schmidt 1995; MacLean et al. 1996). I N T R O D U C T I O N