A recombinant rodent comprises cells containing a pair of genomic dopamine transporter protein alleles, wherein at least one of said alleles is incapable of expressing endogenous dopamine transporter protein. The rodent may be a homozygote, where both of said alleles are incapable of expressing endogenous dopamine transporter protein, or the rodent may be a heterozygote, and one of said alleles expresses endogenous dopamine transporter protein. The rodent is preferably a mouse.
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