Capsaicin-induced dysregulation of acid-base status in the American cockroach

Members of TRP receptor family are involved in response to acidification. Here, we determined the effect of capsaicin, one of the TRP receptor activators, on hemolymph acid-base status in the American cockroach. Periplaneta americana adult individuals were injected with lactic acid (5% or 10%) and exposed to 100 µM capsaicin solution. Hemolymph pH was measured 15 min, 1, 4, 8 and 24 h after lactic acid and capsaicin application with a glass microelectrode. The results demonstrated that cockroaches recover from acidosis within 4 h from acid injection. Capsaicin impaired the buffering capacity of insects' hemolymph, resulting in significant drop of hemolymph pH observed even 24 h after application. Joint action of capsaicin and acidosis reveals new insight into possible mechanism of capsaicin action on TRP receptors in insects.