Figure 4.

γ-Aminobutyric acid type A (GABA_A) receptor activation detrimentally affects memory retrieval. (a, b) Fifteen minutes before the retention trial, (a) muscimol (0.25, 0.5, or 1 μg/μl/side) or (b) diazepam (10, 20, or 40 μg/μl/side) were administered bilaterally into the hippocampus. Latency times measured during the retention trial were reduced by muscimol or diazepam administration in a dose-dependent manner. (c) To test state-dependency of GABAergic drugs, muscimol (1 μg/μl/side) or diazepam (40 μg/μl/side) was administered bilaterally 15 min before both acquisition and retention trial. Data are presented as the means±SEM (n=8–10 per group). ^*p<0.05, compared with the vehicle-treated control group. (d) The effect of muscimol (1 μg/μl/side) or diazepam (40 μg/μl/side) on memory retrieval-induced ERK activation. The mice were killed immediately after the retention trial of passive avoidance task. Data are presented as the means±SEM (n=4 per group). ^*p<0.05, compared with the control group; ^#p<0.05, compared with the vehicle-treated retrieval group. Control, animals exposed to acquisition but not retention trial. (e, f) The motoric effects of muscimol (0.25, 0.5, or 1 μg/μl/side, (e) or diazepam (10, 20, or 40 μg/μl/side, f) in the open field test. Drugs were injected 15 min before the test, and the distance that each mouse moved was recorded for 5 min. Data are presented as the means±SEM (n=10 per group).