Fig. 1

Systemic KOR agonist, U-69,593, failed to induce yawning behavior but increased urination in both female and male rats. A The number of yawning events and, B the increase in urination were evaluated for 120 min after a single subcutaneous administration of U-69,593 at 0.56 mg/kg, apomorphine at 0.05 mg/kg (a non-selective dopamine agonist used as a positive control for yawning) and vehicle-control. The number of yawning was quantified in 30-min intervals. Urination was quantified as the difference between the weight of the individual absorbable underpads before drug administration and 120 min after testing. Female and male data were combined. Data are presented as mean ± SEM and analyzed using two-way (A) or one-way (B) ANOVA followed by Tukey’s multiple comparison test with * representing p < 0.05 in comparison with the control group (n = 12; 6 females/group and 6 males/group)