dizocilpine-maleate and besonprodil

Windup, the frequency dependent build-up of spinal neuronal responses, is implicated in the development of central sensitization of nociceptive pathways. N-methyl-D-aspartate (NMDA) receptors have been shown to be involved in these processes but the role of various receptor subtypes at the spinal level is not fully understood. In our experiments, we compared the inhibitory effect of MK-801 (a nonselective NMDA receptor antagonist, 0.01-3 mg/kg i.v.) and CI-1041 (an NR2B subunit specific NMDA receptor antagonist, 0.3-10 mg/kg i.v.) on the formation of dorsal horn neuronal windup in spinalized rats, in vivo. Both types of antagonist blocked windup considerably at doses not affecting the normal synaptic transmission. These results are in agreement with the well-documented effectivity of NR2B subtype selective NMDA receptor antagonists in chronic pain models and give the first direct evidence that spinal mechanisms are involved in this effect.

Topics: Action Potentials; Analysis of Variance; Animals; Benzoxazoles; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Interactions; Electric Stimulation; Excitatory Amino Acid Antagonists; Excitatory Postsynaptic Potentials; Male; Nerve Fibers; Piperidines; Posterior Horn Cells; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Spinal Cord; Spinal Cord Injuries