CB2 Cannabinoid Receptor Knockout in Mice Impairs Contextual Long-Term Memory and Enhances Spatial Working Memory
Contextual, but not cued, fear memory of CB2R KO mice is impaired. (a) Baseline freezing behavior of mice during the conditioning period. A mouse in a fear conditioning chamber was presented with a tone for 30 s, 3 times every 2 min. During the last 2 s of the tone, an electric foot shock was delivered. The freezing time of KO mice was similar to that of WT mice in each of the 2 min periods. (b) Contextual fear memory was tested 24 h after the fear conditioning. Mice were placed in the same conditioning chamber for 5 min and the freezing time was measured. The freezing behavior was also analyzed in the early (0–2 min) and late (4-5 min) phases of the 5 min period. ; ; -test. (c) Cued fear memory was assayed after the contextual memory test in a modified conditioning chamber. A tone was presented for 3 min and the freezing behavior was monitored before (for 2 min) and during the tone. Error bars represent SEM.