There was no significant difference in 24-h water intake (data not shown) among treatment groups on the pre-drug day. During the 2 treatment days there was a significant effect of dose [F(4,46) = 28.53, p < 0.001] but no significant dose × day interaction (average water intake for the vehicle-treated or 10, 20, 40, or 80 µg/kg clonidine-treated group was 32.5 ± 1.8, 32.0 ± 1.8, 39.5 ± 4.1, 46.9 ± 2.9, and 65.5 ± 2.1 mL/kg/24 h, respectively). Pairwise comparisons using the Fisher’s LSD test revealed that 24-h water intake was increased (p ≤ 0.001) by clonidine at doses of 40 or 80 µg/kg relative to treatment with vehicle, independent of day. On post-treatment days 1 and 2, there was no significant effect of dose or day and no significant dose × day interaction (average 24-h water intake for the vehicle-treated or 10, 20, 40, or 80 µg/kg clonidine-treated group was 34.4 ± 1.9, 34.8 ± 1.9, 34.9 ± 3.5, 32.1 ± 1.8, or 34.3 ± 1.4 mL/kg/24 h, respectively).
