In the present study, alcohol intake remained suppressed for 24 h following termination of 2 days of clonidine treatment. This is not likely due to the continued presence of circulating clonidine since the half-life of clonidine is less than 1 h in rats (Hui et al., 2007). The continued suppression of alcohol intake following termination of clonidine treatment could reflect acute clonidine-induced alterations in α-adrenergic receptors. With more prolonged clonidine treatment (5 consecutive days), suppression of alcohol drinking was maintained over the course of treatment, indicating that drug tolerance to clonidine did not develop. In the 5-day treatment paradigm, the last day of clonidine treatment was Friday, and the first day of post-drug testing did not occur until the following Monday, so the duration of suppression of drinking could not be comprehensively assessed. However, alcohol drinking was no longer suppressed at 72 h after the final clonidine administration, indicating no long-term residual effects of the drug.
