ABSTRACT
<p><b>AIM</b>To investigate the effect of capsaicin on IA and IK in cultured rat trigeminal ganglion (TG) neurons.</p><p><b>METHODS</b>Whole-cell patch clamp technique was used to record the IA and IK before and after capsaicin perfusion at different concentrations.</p><p><b>RESULTS</b>In capsaicin-sensitive (CS) neurons, capsaicin was shown to selectively inhibit IA in dose-dependent manner, the IC50 was 0.99 micromol x L(-1). Yet capsaicin showed no inhibitory effect on IK, capsaicin (10 micromol x L(-1)) only slightly inhibited IK by 13.2%. In capsaicin-insensitive (CIS) neurons, capsaicin (1 micromol x L(-1)) showed no significant inhibitory effect on IA and IK, capsaicin (10 micromol x L(-1)) only slightly inhibited IA and IK by 16.8% and 15.3%, respectively. Neither 1 micromol x L(-1) nor 10 micromol x L(-1) capsaicin showed effect on the G-V curve of IA and IK.</p><p><b>CONCLUSION</b>Capsaicin was found to selectively inhibit the IA current in CS neurons, and this effect may contribute to hyperalgesia when capsaicin was first used.</p>
