Effects of tramadol superfusion on sEPSCs and sIPSCs in substantia gelatinosa neurons.

<p>Superfusion of tramadol at clinically relevant concentration (10 μM) onto the surface of the spinal cord had no effect on sEPSCs (A upper trace). At high concentration (100 μM) superfusion of tramadol inhibited sEPSCs and induced outward currents (A middle trace). In the presence of naloxone 1 μM, superperfusion of tramadol 100 μM had no effect on sEPSCs (A lower trace). Superfusion of tramadol had no effect on sIPSCs at clinically relevant concentration (10 μM) (B upper trace), but enhanced sIPSCs at high concentration (100 μM) (B middle trace). The enhancement at high concentration was observed even in the presence of naloxone (B lower trace). These effects were summarized in (C). Data are the mean ± SEM. Asterisks indicate a significant difference from the control (*<i>p</i> < 0.05) (paired <i>t</i>-test).