In the first study, 66 male mice, 29 of the C57BL/6 strain (B6) and 37 of DBA/2 strain (D2) were used. Mice were obtained from The Scripps Research Institute breeding facility, weighing between 19 and 30 g. In the second study, 52 male mice, 15 HAP-1 mice, 18 LAP-1 mice and 19 HS/Ibg mice were used. HAP-1, LAP-1 and HS/Ibg mice were obtained from Indiana University and were from the 20th breeding generation of the first replicate line of HAP and LAP mice, as previously described (Slawecki et al., 2003). HS/Ibg mice were obtained from the Institute for Behavioral Genetics at the University of Colorado and served as the progenitor stock (Grahame et al., 1999b). They were from the 67th breeding generation. All mice were housed 3–4 per cage in controlled temperature and lighting conditions, with food and water ad libitum for the duration of the study. Detailed description of the environmental conditions of mice from both studies can be found elsewhere (Ehlers and Somes, 2002, Slawecki et al., 2003). The work described herein adheres to the guidelines stipulated in
