Fig. 5.

Pre-exposure naloxone (NLX) or HY6-F9 in cumulative fentanyl challenge and NLX dose-response. A–B, Rats pretreated with 40 mg/kg mAb were treated with saline or 0.1 mg/kg NLX s.c. Fifteen minutes after NLX, rats were challenged at 15-minute intervals with increasing doses of fentanyl, to a cumulative dose of 0.5 mg/kg. (A) Antinociception measured as latency to respond, and (B) oxygen saturation measured by pulse oximetry. (C and D) Rats pretreated with 10 or 40 mg/kg mAb were given 2.25 mg/kg fentanyl. Ten minutes after fentanyl, and at 4-minute intervals, rats were given increasing doses of NLX to reverse overdose. (C) Antinociception measured as latency to respond, and (D) oxygen saturation measured by pulse oximetry. Data are mean ± S.E.M. ****p<0.0001, ***p<0.001, **p<0.01, *p<0.05 relative to saline (control).