Fig. 2.

Reversal of the ventilatory-depressant effects of fentanyl by MCAM and naloxone. Rats received an intravenous infusion of 0.178 mg/kg fentanyl at “0” minutes (arrows) and a second infusion of vehicle, (squares, both panels), MCAM (left panels), or naloxone (right panels) at “5” minutes. Upper panels include data for vehicle, 0.1, 1.0, and 10.0 mg/kg; lower panels include data for vehicle, 0.0001, 0.001, and 0.01 mg/kg. The gray bar represents the 95% CI for minute volume under control conditions (saline followed by vehicle). Insets represent the area under the curve (AUC) for MCAM or naloxone curves compared with vehicle curves. Asterisks indicate that AUC obtained after the administration of an antagonist was significantly different from AUC after vehicle, P < 0.05. Ordinates: minute volume plotted as percent of control and averaged among eight rats ± 1 S.E.M. Abscissae: time in minutes. CI, confidence interval.