Table 1.

Effect of rolipram and papaverine on basal and haloperidol-induced levels of dopamine and dopamine metabolites DOPAC and HVA

	DA	DOPAC	HVA	DOPAC/DA	HVA/DA
Control	15.63 ± 0.45	0.77 ± 0.05	1.12 ± 0.08	5.32 ± 0.21	7.72 ± 0.32
Haloperidol	12.80 ± 0.89	2.90 ± 0.20**	2.94 ± 0.24**	22.67 ± 0.52**	22.93 ± 0.62**
Rolipram	18.22 ± 1.33	1.05 ± 0.04	1.25 ± 0.10	5.85 ± 0.29	6.86 ± 0.24
Papaverine	15.31 ± 1.38	1.05 ± 0.13	1.38 ± 0.12	6.80 ± 0.36	9.01 ± 0.18
Haloperidol plus rolipram	12.72 ± 0.37	4.06 ± 0.16**,^††,^¶¶	2.81 ± 0.14**,^††	31.96 ± 1.14**,^††,^¶¶	22.02 ± 0.60**,^††
Haloperidol plus papaverine	11.69 ± 1.20	2.82 ± 0.23**,^§§	2.27 ± 0.24**,^§§,^¶	24.52 ± 1.04**,^§§	19.65 ± 1.18**,^§§,^¶¶

Mice were treated with vehicle, rolipram (10 mg/kg) alone, papaverine (30 mg/kg) alone, or in combination with haloperidol (0.3 mg/kg) and killed 30 min later by focused microwave irradiation. Striatum was dissected and analyzed for dopamine (DA) and its metabolites, DOPAC and HVA. Data represent means ± SEM for 4–5 experiments. **p < 0.01 compared with control; ^†† p < 0.01 compared with rolipram alone; ^§§ p < 0.01 compared with papaverine alone; ^¶ p < 0.05, ^¶¶ p < 0.01 compared with haloperidol alone; one-way ANOVA followed by Newman–Keuls test.