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 the NIH Guide for the Care and Use of Laboratory Animals (NIH publication No. 80–23, revised 1996) and was reviewed and approved by The Scripps Research Institute’s Institutional Animal Care and Use Committee.
