Sensory denervation with capsaicin does not influence the critical ischemia time in rat island flaps

Capsaicin causes release and long-term depletion of neuropeptides from sensory neurons. Recently, critical rat pedicle flaps pretreated with capsaicin have shown decreased survival. In the present study, the effect of systemic capsaicin pretreatment on the no-reflow phenomenon was investigated in the rat. Effective depletion of neuropeptides was confirmed with functional tests and immunohistochemistry. Groin island flaps were exposed to 4, 6, 8, 10 or 12 hours of warm ischemia, and flap survival was judged one week postoperatively. In contrast to previously reported negative effects on pedicle flap survival after pretreatment with capsaicin, the present study showed no difference in flap survival between capsaicin-pretreated rats and controls. It is concluded that depletion of neuropeptides from sensory neurons does not have negative effects on the tissue's ability to withstand prolonged complete ischemia. As this contrasts with the findings in critical pedicle flaps, the influence of sensory neuropeptides and the necrosis mechanisms are likely to be different in these two types of ischemic conditions.