Role of postsynaptic density protein-95 in the maintenance of peripheral nerve injury-induced neuropathic pain in rats

Our previous work has demonstrated that postsynaptic density protein-95, a molecular scaffolding protein that binds and clusters N-methyl-d-aspartate receptors at neuronal synapses, plays an important role in the development of peripheral nerve injury-induced neuropathic pain. The current study further investigated the possible involvement of postsynaptic density protein-95 in the maintenance of neuropathic pain. Mechanical and thermal hyperalgesia were induced within 3 days and maintained for 15 days or longer after unilateral injury to the fifth lumbar spinal nerve. The rats injected intrathecally with postsynaptic density protein-95 antisense oligodeoxynucleotide every 24 h for 4 days from day 7 to day 10 post-surgery exhibited not only a marked decrease in spinal cord postsynaptic density protein-95 protein expression but also a significant reduction in mechanical and thermal hyperalgesia on day 11 post-surgery. The rats injected with sense oligodeoxynucleotide did not display these changes. However, in the rats without nerve injury, postsynaptic density protein-95 antisense oligodeoxynucleotide given intrathecally every 24 h for 4 days did not affect responses to mechanical and thermal stimulation. In addition, postsynaptic density protein-95 antisense oligodeoxynucleotide did not change locomotor activity of experimental animals. Our results indicate that the deficiency of postsynaptic density protein-95 protein in the spinal cord significantly attenuates nerve injury-induced mechanical and thermal hyperalgesia during both the development and maintenance of chronic neuropathic pain. These results suggest that postsynaptic density protein-95 might be involved in the central mechanisms of chronic neuropathic pain and provide a novel target for development of new pain therapies.