Fig. 7.

Effects of fentanyl on tail-withdrawal latency from warm water 1, 5, and 21 days after intravenous (left) or subcutaneous (right; replotted with permission from Gerak et al., 2019b) administration of 10 mg/kg MCAM. Inset summarizes data (maximum possible effect) for a cumulative dose of 0.1 mg/kg fentanyl under control conditions (C) and 1, 5, and 21 days after intravenous or subcutaneous administration of 10 mg/kg MCAM. Asterisks indicate tail-withdrawal latency that was different between MCAM administered intravenously or subcutaneously, P < 0.05. Ordinate: average latency (±1 S.E.M.) to remove tails from 50°C water expressed as a percentage of control and averaged among eight rats. Abscissae: dose of fentanyl administered intraperitoneally in mg/kg body weight. S represents the effects of saline.