The effects of aging on thermal hyperalgesia and tactile-evoked allodynia using two models of peripheral mononeuropathy in the rat.

The effects of aging on the behavioral manifestations of neuropathic and inflammatory pain were investigated using two models of peripheral nerve injury. The left sciatic nerve of young and aged Fischer 344 FBNF1 hybrid rats (4-6 and 24-26 months old, respectively) was ligated using either the chronic constriction injury (CCI) model of Bennett and Xie or the partial sciatic nerve ligation (PSNL) model of Seltzer et al. A plantar analgesic meter was used to assess age-related differences in CCI- or PSNL-induced thermal hyperalgesia, and nerve injury-induced tactile-evoked allodynia was assessed with von Frey filaments. Aged animals subjected to the PSNL procedure developed a more vigorous and longer lasting thermal hyperalgesic response than did aged rats post-CCI. The CCI model incorporates a more prominent peripheral inflammatory component than the PSNL model. These data support the notion that the peripheral inflammatory response is diminished in aged rats.