Inhibition of hilar GABAergic interneuron activity impaired spatial memory retrieval but not memory retention.

(A) Protocols of mice used and laser illumination during hidden platform (H1–5) and probe (P-24 h, P-48 h, P-72 h) trials in the MWM test. (B) Learning curves of I12b-Cre mice injected with AAV1-DIO-eNpHR3.0-eYFP virus without laser illumination in the hidden platform trials (H-Off) of the MWM test. Points represent averages of daily trials. H, hidden platform sessions (two trials/session, two sessions/day); H0, first trial on H1. Y-axis indicates time to reach the target platform (escape latency). Values are mean ± SEM and statistically evaluated by repeated measures ANOVA. (C–E) Percent time spent in the target quadrant versus the other quadrants in the probe trial performed 24 (P-24 h), 48 (P-48 h), or 72 (P-72 h) hours after the last hidden platform trial with (On) or without (Off) laser illumination. Values are mean ± SEM. *p<0.05, **p<0.01 (two tailed and unpaired t-test). F–H, Platform crossings in the probe trial performed 24 (P-24 h), 48 (P-48 h), or 72 (P-72 h) hours after the last hidden platform trial with (On) or without (Off) laser illumination. Values are mean ± SEM. n = 8 mice/group. *p<0.05, ^#p = 0.05 (two tailed and unpaired t-test).