Activation of CB1R on glutamatergic neurons inhibits network bursting. A, Histogram of normalized spontaneous burst rates in different experimental conditions. Connected circles represent individual experiments. WIN had no effect on average in naive conditions (n = 11) but significantly decreased bursting in disinhibited cultures (in Ptx + CGP; n = 8). This effect was prevented by AM251 (n = 4). B, Sample traces illustrating the inhibitory effect of WIN in the presence of Ptx and CGP. C, Summary histogram of the average effect of WIN in different experimental conditions in cultures from rat cortices (left) and in cultures from cortices of GABA-CB1R KO, Glu-CB1R KO, and their respective wild-type (wt) littermates (right).