CB1R agonists reduce GABA release by presynaptic mechanisms. A, mIPSC frequency was reduced after WIN55,212,2 application to the slice. B, The amplitude of the mIPSC was not affected by WIN55,212,2 treatment, consistent with a presynaptic mechanism. C, Bar graph showing the averaged actions of WIN55,212,2 on the frequency (left) or the amplitude (right) of mIPSCs in MCH neurons. The asterisk indicates statistical significance. D, No effect of WIN55,212,2 on IPSC frequency (left) or amplitude (right) was observed when slices were preincubated with the CB1R antagonist AM251. Error bars indicate SEM. Win, WIN55,212,2; Ctrl, control.