Based on the findings noted above, variations in the expression of DAT (within the human range) may have greater effects on responses to amphetamine-like drugs than responses to cocaine. The acute locomotor stimulating effects of cocaine are largely eliminated in homozygous DAT KO mice (Giros, et al., 1996; Morice, Denis, Giros, & Nosten-Bertrand, 2004; Sora, et al., 1998) but heterozygous mice are largely unaffected. Similarly, sensitization is not observed in DAT KO mice even after extended periods of habituation to normalize activity (Mead, Rocha, Donovan, & Katz, 2002). In another paradigm, homozygous DAT KO mice exhibit neither conditioned locomotion nor context-dependent sensitization (Hall, et al., 2009), yet heterozygous DAT KO mice are not different from wildtype mice.
