UP-REGULATION OF SPINAL GLUTAMATE RECEPTORS IN CHRONIC PAIN

Recent studies indicate that glutamate binding to N-methyl-D-aspartate receptors in the spinal cord is involved in triggering the developmen t of chronic pain.(16) However, the processes which directly underlie the increased pain remain unclear, Here we report that, following peri pheral nerve injury (ligation of the sciatic nerve) in the rat, there is an increase in immunoreactive labelling of non-N-methyl-D-aspartate , AMPA -amino-3-hydroxy-5-methyl-4-isoxazoleproprionate), glutamate re ceptors in the superficial laminae of the lumbar spinal cord ipsilater al to the ligation, The increase in AMPA receptor expression peaks 14 days after nerve ligation and decreases 35 days post-ligation, corresp onding to the time-course of heightened sensitivity to mechanical and thermal noxious stimuli (hyperalgesia) induced by the ligation. Given evidence that AMPA receptors in the superficial laminae mediate fast n ociceptive transmission in the spinal Cord,(9,25,26) our findings sugg est that an upregulation of spinal AMPA receptors contributes to hyper algesia following peripheral nerve injury. Copyright (C) 1996 IBRO.