Table 2.

Levels of dopamine (DA) and its major metabolites (DOPAC and HVA) in the limbic forebrain area from wild-type (WT) and dopamine D₃ receptor knock-out (D₃KO) mice in the presence or absence of morphine (MRP)

	DA             DOPAC            HVA			DA ratio
	(ng/gm wet tissue)
WT
Basal	6918.1  ± 297.5	632.8  ± 40.4	461.3  ± 18.2	0.157  ± 0.004
MRP	6517.1  ± 278.6	1067.9  ± 43.82-160	817.3  ± 26.32-165	0.290  ± 0.0062-165
D3KO
Basal	6525.7  ± 62.3	585.7  ± 1.4	434.7  ± 5.9	0.156  ± 0.002
MRP	6398.9  ± 532.3	1110.9  ± 85.92-160	714.2  ± 51.62-160	0.286  ± 0.0072-165

Each value represents the mean with SEM. The dopamine turnover (DA ratio) was calculated as follows: (DOPAC + HVA)/DA.

F2-160: p < 0.01,

F2-165: p< 0.001 versus basal group.