2. Materials and methods
2.1. Animals
Adult male SpragueeDawley rats (300e325 g at the time of
testing, Institute for Behavioral Genetics, Boulder, Colorado) were
kept on a 12-h reverse light/dark cycle; all experiments were
conducted during the dark phase. Animals were pair-housed until
catheter implantation, after which they were housed individually.
Standard lab chow and water were available ad libitum. Procedures
were performed in accordance with standard ethical guidelines
(National Institutes of Health Guide for the Care and Use of Laboratory
Animals) and were approved by the Institutional Animal Care
and Use Committee at the University of Colorado Boulder.