Figure 8.

Effects of ML321 on D2R-mediated hypothermia or D3R-mediated yawning in rats. Measurements of hypothermia and yawning were performed as described in the Methods. All data are presented as the mean ± SEM. (A) Measurement of hypothermia: change in rats’ body temperature following injection (s.c.) with vehicle (0.0 mg/kg) or 1.0, 3.2, or 10.0 mg/kg ML321 and 1.0 mg/kg sumanirole (SUM). Experimental groups contained 6 animals each except for the 10.0 mg/kg ML321 + vehicle group, which contained 3 animals. For the ML321 + sumanirole groups following a significant effect of ML321 dose in one-way ANOVA [F(3,20) = 14.69, p < 0.001], pairwise comparisons to vehicle were made post hoc using Dunnett’s tests (two-tailed): ***p < 0.001, significantly different from 0.0 mg/kg ML321 (vehicle) + 1.0 mg/kg sumanirole. For the 10 mg/kg ML321 + vehicle group, the data are presented for reference but were not statistically analyzed given the small number of animals tested. (B) Measurement of yawning: number of yawns made in 60 min following injection (s.c.) with vehicle (0.0 mg/kg) or 3.2 or 10.0 mg/kg ML321 and 0.1 mg/kg pramipexole (PRAM). Experimental groups contained 8 animals except for the 10.0 mg/kg ML321 + vehicle group, which contained 3 animals. For the ML321 + pramipexole groups, one-way ANOVA for dose was not significant. [F(2,21) = 0.03, p = 0.96]. For the 10 mg/kg ML321 + vehicle group, the data are presented for reference but were not statistically analyzed given the small number of animals tested. (C) To obtain a time course of pramipexole-induced yawning, the 60 min observation session in panel (B) was divided into 4 blocks of 15 min each, and the data were reanalyzed as the mean yawns in each time-block. Two-way ANOVA detected a significant effect of block [F(3,84) = 16.54, p < 0.001]; however, the mean yawns/blocks were not affected by the ML321 dose (non-significant main effect and interaction).