Fig. 1. Effects of (a) haloperidol and (b) olanzapine on the Δ⁹-tetrahydrocannabinol-induced decrease in the number of correct choices in the radial maze test. Δ⁹-Tetrahydrocannabinol (6 mg/kg) was injected i.p. 60 min prior to testing. Haloperidol (0.03–0.3 mg/kg) and olanzapine (0.01–0.1 mg/kg) were injected i.p. 30 min prior to testing. Values are expressed as means ± S.E.M. ^††P < 0.01 compared with vehicle, P < 0.05, P < 0.01 compared with Δ⁹-tetrahydrocannabinol alone. The number of animals is shown at the bottom of each column.

Fig. 2. Effects of (a) haloperidol and (b) olanzapine on the Δ⁹-tetrahydrocannabinol-induced increase in the number of errors in the radial maze test. Δ⁹-Tetrahydrocannabinol (6 mg/kg) was injected i.p. 60 min prior to testing. Haloperidol (0.03–0.3 mg/kg) and olanzapine (0.01–0.1 mg/kg) were injected i.p. 30 min prior to testing. Values are expressed as means ± S.E.M. ^††P < 0.01 compared with vehicle, P < 0.01 compared with Δ⁹-tetrahydrocannabinol alone. The number of animals is shown at the bottom of each column.

Fig. 3. Effects of (a) haloperidol and (b) olanzapine on running time in Δ⁹-tetrahydrocannabinol-treated rats. Δ⁹-Tetrahydrocannabinol (6 mg/kg) was injected i.p. 60 min prior to testing. Haloperidol (0.03–0.3 mg/kg) and olanzapine (0.01–0.1 mg/kg) were injected i.p. 30 min prior to testing. Values are expressed as means ± S.E.M. ^†P < 0.05, ^††P < 0.01 compared with vehicle. The number of animals is shown at the bottom of each column.

Fig. 4. Effects of (a) haloperidol and (b) olanzapine on the Δ⁹-tetrahydrocannabinol-induced decrease in ACh release in the dorsal hippocampus in rats. Δ⁹-Tetrahydrocannabinol (6 mg/kg, i.p.) was administered 40 min after sampling was started. Haloperidol (0.3 mg/kg, i.p.) and olanzapine (0.1 mg/kg, i.p.) were administered 70 min after sampling was started. Values are expressed as percentages (mean ± S.E.M.) of the baseline concentration. ^††P < 0.01 compared with vehicle, P < 0.05, P < 0.01 compared with Δ⁹-tetrahydrocannabinol alone, ^#P < 0.05 compared with the baseline (BL-1).