Detailed methods used for the screen have been reported previously [23]. Briefly, adult DBA/2J (D2) male mice (Jackson Labs) were administered three doses of 90 mg/kg N-ethyl-N-nitrosourea (ENU, indicated by *) (Sigma) intraperitoneally at weekly intervals as described [35]. Approximately 12 weeks after the last injection, these mice recovered fertility and were bred to non-mutagenized D2 female mice to produce G1 mutagenized male mice. These mutated D2* males were then backcrossed to B6 females to produce B6D2* G2 animals that were screened for increased locomotor activity. High-scoring animals were then backcrossed repeatedly to B6 females for heritability testing and QTL mapping.
