CAPSAICIN BLOCKS TETRODOTOXIN-RESISTANT SODIUM POTENTIALS AND CALCIUMPOTENTIALS IN UNMYELINATED C-FIBERS OF BIOPSIED HUMAN SURAL NERVE IN-VITRO

Topical application of capsaicin has been tested recently for treatmen t of painful peripheral neuropathy. In the present study, effects of c apsaicin were explored on compound action potentials of isolated fasci cles from human sural nerve biopsies. Capsaicin reduced the C fibre co mponent by 30-60%; the remaining C fibres were not sensitive to the dr ug. A good correlation was found between the sensitivity of C fibres t o capsaicin and their resistance to tetrodotoxin (TTX), i.e. C fibre a ction potentials recorded in the presence of TTX were completely block ed by capsaicin. Calcium action potentials seen after inhibition of ax onal potassium conductances were also completely suppressed, The data indicate that application of capsaicin nearby human peripheral nerves might prevent action potential conduction in specific subtypes of C fi bres.