Table 1.

d -Amphetamine activation of ERK1/2 in striatal neurons in wild-type, Drd1a-KO, and DARPP-32-KO mice

Striatal region	Wild type	Drd1a KO	p value	Wild type	DARPP32 KO	p value
Dorsal lateral	5.2	6.0	0.268	4.7	5.5	0.268NS
Dorsal medial	19.7	21.3	0.322	18.7	21.0	0.294NS
Accumbens	55.8	19.3	0.0011**	47.3	18.5	0.0011**

Counts of neurons showing phospho-ERK1/2 in different regions of the striatum and nucleus accumbens from animals in treatment groups described in this study. Treatment groups with d -amphetamine (10 mg/kg, i.p.) included wild-type and Drd1a knock-out and DARPP-32 knock-out animals. Cell counts are the average from six animals per treatment group (n = 6) measured in a 100 μm² area in each region. Wilcoxon's rank sum test shows that there is only a significant reduction (**p < 0.01) in amphetamine induction of phospho-ERK1/2 neurons in the nucleus accumbens in both Drd1a KO and DARPP-32 KO animals compared with wild type.

**p < 0.01 < NS.