HIC severity waxes and wanes during the hours of withdrawal, and shows dose- and duration-dependent effects of alcohol exposure. Many studies have explored the genetic bases of withdrawal severity in mice using the HIC as the index of severity, e.g. (Crabbe, 1996; Homanics et al., 1998; Metten and Crabbe, 2005), and thus this study focused on the existing QTLs mapped for withdrawal HIC. The severity of the HIC also increases in severity with repeated cycles of exposure, a phenomenon likened to the “kindling” of severity of successive withdrawal episodes in humans (Becker, 1996). Several other behavioral signs of withdrawal have been documented in rodents, but, as there were no available QTL data, they were not considered for the present set of analyses.
