Research Article

CB2 Cannabinoid Receptor Knockout in Mice Impairs Contextual Long-Term Memory and Enhances Spatial Working Memory

Figure 5

Acute blockade of CB2Rs had little effect on fear memory. (a) Adult male C57BL/6J mice were fear-conditioned with a tone and a foot shock, as illustrated in Figure 1(a). The animals were injected with AM630 (3 mg/kg, i.p.), a CB2R antagonist, 3 min after the conditioning. (b) Baseline freezing behavior of mice during the conditioning session. The mice were randomly divided into two groups for injection with AM630 or vehicle. (c) Contextual fear memory of AM630-treated mice was not significantly different from that of control mice. The freezing time was counted during a 5 min session and also analyzed for the first 2 and the last 1 min of the session. (d) Cued fear memory was not affected by acute treatment with AM630. A tone was presented for 3 min. There was no significant difference in freezing behavior between the two groups either before or during the tone. Error bars represent SEM.