Figure 5.

Stress increases anxiety-like behavior via 2-AG signaling in the BLA. A, Percentage of total time (5 min) spent in the center of the open field by rats pretreated with either vehicle (Veh) or the CB1 receptor antagonist SR in the BLA and exposed to restraint stress (30 min; Stress) or returned to the home cage (Control). Stress reduced the percentage of time spent in the center, indicating an increase in anxiety-like behavior, in rats that received bilateral vehicle injections in the BLA, but not injections of SR. Intra-BLA blockade of CB1 receptors in unstressed control rats led to a decrease in percentage time spent in the center, indicating an anxiolytic tone exerted by CB1 receptor activation in the BLA. B, Percentage of total time (5 min) spent in the center of the open field by rats pretreated with either vehicle (Veh) or the 2-AG synthesis inhibitor THL in the BLA and exposed to restraint stress (30 min; Stress) or returned to the home cage (Control). Stress reduced the percentage of time spent in the center in rats that received bilateral vehicle injections in the BLA, and this effect was abolished by intra-BLA blockade of 2-AG synthesis. Intra-BLA blockade of 2-AG synthesis had no effect on center time in unstressed control rats, suggesting that the anxiogenic effect of blocking CB1 receptors was not dependent on 2-AG synthesis. C, Percentage of total time (5 min) spent in the open arms of the elevated plus maze by rats pretreated with either vehicle (Veh) or THL in the BLA and exposed to restraint stress (30 min; Stress) or returned to the home cage (Control). D, Number of entries into the open arms of the elevated plus maze by rats pretreated with vehicle (Veh) or THL in the BLA and undergoing stress or no stress (Control). The open-arm time and open-arm entries in the elevated plus maze revealed a similar pattern to that observed in the open field, but did not show a significant effect of drug or stress. **p < 0.01 vs Control/Veh; #p < 0.05 vs Stress/Veh.