Transmission of chronic nociception by spinal neurons expressing the substance P receptor

Substance P receptor (SPR)-expressing spinal neurons were ablated with the selective cytotoxin substance P-saporin. Loss of these neurons resulted in a reduction of thermal hyperalgesia and mechanical allodynia associated wit h persistent neuropathic and inflammatory pain states. This Loss appeared t o be permanent. Responses to mildly painful stimuli and morphine analgesia were unaffected by this treatment. These results identify a target for trea ting persistent pain and suggest that the small population of SPR-expressin g neurons in the dorsal horn of the spinal cord plays a pivotal role in the generation and maintenance of chronic neuropathic and inflammatory pain.