Twenty-five (25) rats, 14 P and 11 NP male rats, of the 42nd generation, bred at Indiana University were received at The Scripps Research Institute weighing 281–410 g. All rats had ad libitum access to food and water. A detailed description of the environmental conditions of rats can be found elsewhere (Ehlers et al., 1999). 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.
