Fig. 5.

Combined antagonism of CB1R and CB2R is necessary to feminize the total frequency of male play behavior. A, B, Administration of AM281 (a CB1-specific antagonist) or AM630 (a CB2-specific antagonist) to neonatal males (PN0–3) did not alter the total frequency of rough-and-tumble play events. C–E, Coadministration of AM281 and AM630 decreased the total frequency of rough-and-tumble play events by males to the level observed in females and had no effect on female play. Frequency of play is an average over all days of analysis, with the average for each individual day shown in the insets (B, D, E). **p < 0.01, ***p < 0.001, n = 6–10.