The maintenance of individual differences in the sensitivity of acute and neuropathic pain behaviors to electroacupuncture in rats.

Abstract

"Responder" Sprague-Dawley (SD) rats that were sensitive to electroacupuncture (EA) in an acute thermal pain test (i.e. tail flick latency [TFL] test) maintained sensitivity to EA in the warm allodynia test after peripheral nerve injury. Similarly, the "non-responder" SD rats that were insensitive to EA in the TFL test were also insensitive to EA in the allodynia test. The EA-induced analgesic effects in the TFL test were significantly higher in CCK-A receptor deficient, Otsuka Long-Evans Tokushima Fatty (OLETF) rats than in their littermates, Long-Evans Tokushima Otsuka (LETO) rats. Similarly, the anti-allodynic effects of EA were significantly greater in OLETF rats than in LETO rats. These results suggest that the individual differences in the sensitivity of acute pain behavior to EA were maintained in neuropathic pain behavior following peripheral nerve injury, and that CCK-A receptor expression plays an important role in mediating this phenomenon.