Bilateral dialysis of 100 μM DAMGO during the day (filled circles, n=7) significantly (P<0.002) increased ventilation (V̇I, panel A) and breathing frequency (f, panel B) but did not alter (P<0.446) tidal volume (VT, panel C) compared to dialysis of mCSF alone (open circles, n=7). Data are means ± SE. Dialysis of 100μM DAMGO occurred between 60 and 120 minutes (indicated by solid line). The values shown during and after DAMGO dialyses are the percent of the last 15 minutes prior to DAMGO dialyses. The F and P values are interaction terms from two-way repeated measures ANOVA using dose and time as factors. Asterisks denote values different between open and closed symbols ((P < 0.05), post hoc test).