Increasing endocannabinoid signaling decreased AMPA mPSC frequency. A, Representative traces of mPSCs from a motoneuron before (black trace) and 20 min after bath addition of the endocannabinoid reuptake blocker AM 404, 20 μm (gray trace). B, Superimposed traces of averaged AMPA mPSC (left) and GABA mPSC (right) before (black trace) and after bath addition of AM 404 (gray trace). C, Summary of the effect of AM 404 on mPSC frequency. *p = 0.001. D, Cumulative distribution plot showing the increase in the AMPA mPSC IEI (reduction in frequency) after AM 404 addition. E, Summary of the effect of AM 404 on mPSC amplitude. No effect on AMPA mPSC amplitude was found in AM 404 but GABA mPSC amplitude was significantly reduced. *p = 0.003.