Contribution of NMDA and non-NMDA Glutamate Receptors to Locomotor Pattern Generation in the Neonatal Rat Spinal Cord

Proc Biol Sci. 1997 Jun 22;264(1383):877-84. doi: 10.1098/rspb.1997.0122.

Abstract

The motor programme executed by the spinal cord to generate locomotion involves glutamate-mediated excitatory synaptic transmission. Using the neonatal rat spinal cord as an in vitro model in which the locomotor pattern was evoked by 5-hydroxytryptamine (5-HT), we investigated the role of N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors in the generation of locomotor patterns recorded electrophysiologically from pairs of ventral roots. In a control solution, 5-HT (2.5-30 microM) elicited persistent alternating activity in left and right lumbar ventral roots. Increasing 5-HT concentration within this range resulted in increased cycle frequency (on average from 8 to 20 cycles min-1). In the presence of NMDA receptor antagonism, persistent alternating activity was still observed as long as 5-HT doses were increased (range 20-40 microM), even if locomotor pattern frequency was lower than in the control solution. In the presence of non-NMDA receptor antagonism, stable locomotor activity (with lower cycle frequency) was also elicited by 5-HT, albeit with doses larger than in the control solution (15-40 microM). When NMDA and non-NMDA receptors were simultaneously blocked, 5-HT (5-120 microM) always failed to elicit locomotor activity. These data show that the operation of one glutamate receptor class was sufficient to express locomotor activity. As locomotor activity developed at a lower frequency than in the control solution after pharmacological block of either NMDA or non-NMDA receptors, it is suggested that both receptor classes were involved in locomotor pattern generation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 2-Amino-5-phosphonovalerate / pharmacology
  • 6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
  • Animals
  • Animals, Newborn
  • Dose-Response Relationship, Drug
  • Excitatory Amino Acid Antagonists / pharmacology*
  • Motor Activity / drug effects
  • Motor Activity / physiology*
  • Piperazines / pharmacology
  • Rats
  • Rats, Wistar
  • Receptors, Glutamate / physiology*
  • Receptors, N-Methyl-D-Aspartate / physiology*
  • Serotonin / pharmacology*
  • Serotonin Antagonists / pharmacology
  • Spinal Cord / drug effects
  • Spinal Cord / physiology*
  • Spinal Nerve Roots / drug effects
  • Spinal Nerve Roots / physiology*

Substances

  • Excitatory Amino Acid Antagonists
  • Piperazines
  • Receptors, Glutamate
  • Receptors, N-Methyl-D-Aspartate
  • Serotonin Antagonists
  • Serotonin
  • 6-Cyano-7-nitroquinoxaline-2,3-dione
  • 2-Amino-5-phosphonovalerate
  • 1-(3-chlorophenyl)piperazine