DOES PAIN DAMAGE SPINAL-CORD NEURONS - TRANSSYNAPTIC DEGENERATION IN RAT FOLLOWING A SURGICAL INCISION

In prior studies, rats with a chronic constriction injury to the sciat ic nerve have been found to have small- to medium-sized, pyknotic, and hyperchromatic neurons ('dark neurons'; DNs) in spinal dorsal horn la minae I-III. It has been proposed that DNs are produced by an excitoto xic insult involving N-methyl-D-aspartate receptor activation subseque nt to ectopic nociceptor discharge, and that at least some DNs are inh ibitory interneurons whose functional impairment or death contributes to a central state of hyperexcitability that underlies neuropathic hyp eralgesia and allodynia. We show here that laminae I-III DNs are also present 2 days after a surgical procedure that does not include major nerve damage. We propose that this is also the result of a nociceptor- driven excitotoxic insult and that the functional impairment of the af fected neurons may contribute to postoperative pain and tenderness.