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The lamprey CNS has been utilized extensively as a model system for investigating the networks underlying vertebrate motor behavior.The locomotor networks can be activated by application of glutamate agonists,like NMDA,to the isolated spinal cord preparation.Many spinal neurons are capable of generating pacemaker-like membrane potential oscillations upon activation of NMDA receptors.These oscillations rely on the voltage-dependent properties of NMDA receptors in interaction with voltage-dependent and calcium-dependent potassium channels,as well as low-voltage activated calcium channels.Upon membrane depolarization,influx of calcium will activate calcium-dependent potassium channels that in turn will contribute to repolarization and termination of the depolarized phase.The appearance of the NMDA-induced oscillations varies markedly between spinal cord preparations; they may either have a pronounced,depolarized plateau phase,or be characterized by a short-lasting depolarization lasting around 200-300 ms without a plateau.