Effects of triclosan on the rat phrenic nerve-diaphragm preparation.

It has been reported that the lipid soluble, anti-inflammatory drug triclosan, which is currently used in toothpastes and mouthrinses, may reduce pain. This may be an aspect of the anti-inflammatory effect of triclosan, which probably reduces the production of prostaglandin PGE2. However, triclosan may also exhibit a direct analgesic effect through an effect on excitable membranes. The aim of the present study was to examine the possible effect of triclosan on the nerve action potential, on the neuromuscular transmission and on the excitation-contraction coupling of skeletal muscle. Phrenic nerve-hemidiaphragm preparations, as well as isolated phrenic nerves, were dissected from Wistar albino rats and mounted by standard methods in Tyrode solution. Both during indirect and direct stimulation, the preparations were irreversibly inhibited by triclosan at concentrations higher than 5.0 x 10(-6)M. At low concentrations, the inhibition of the twitches during indirect stimulation and of the compound action potential was probably caused by a threshold increase for excitation of the phrenic nerve. At high concentrations, an additional inhibitory effect at the neuromuscular junction was disclosed. The directly stimulated preparation was also probably inhibited by an increase of the threshold for initiation of the muscle action potentials. In addition, a reduced KCl contracture and an acceleration of the caffeine contracture indicated an interaction with the sarcolemma. These results suggest that the analgesic effect of triclosan may be due to a direct interaction with excitable membranes.