Knock down of spinal NMDA receptors reduces NMDA and formalin evoked behaviors in rat

Chronic pain remains a major health problem afflicting an estimated 70% of patients with advanced cancer and inflammatory disorders, and up to 94% of patients with spinal cord injuries. Although progress has been made in the pharmacotherapy of chronic pain management, such as usage of adjuvant drugs and more effective methods of drug delivery, the mainstay of clinical pain management still depends on opiates. NMDA receptor activation, at the level of the spinal cord has been shown to play an important role in the facilitation of nociception (pain) in several animal models. Unfortunately, potent NMDA receptor antagonists, such as MK-801 and APV, have toxic properties and low safety margins that preclude their clinical use. We present evidence which indicates that the use of antisense oligonucleotides targeted to the NMDA-R1 receptor subunit (AS-NMDA-R1), but not sense, abolishes NMDA and formalin induced behaviors. Moreover, we demonstrate that spinal administration of AS-NMDA-R1 results in the abolition of staining for immunoreactive NMDA-R1 in the spinal cord. These data provide novel evidence supporting the feasibility of the use of gene therapy approaches in the management of neuropathic pain.