Skip to main content
. Author manuscript; available in PMC: 2022 Apr 27.
Published in final edited form as: Pharmacol Biochem Behav. 2021 Jul 21;208:173242. doi: 10.1016/j.pbb.2021.173242

Fig. 2.

Fig. 2.

Schematic of the cumulative dose procedure for antinociceptive assessments of fentanyl-related substances in warm-water tail-withdrawal tests (FEN; fentanyl used as example). SAL and VEH refer to pretreatment of saline (i.e., naltrexone’s vehicle; control for antagonism experiments) and fentanyl’s vehicle (saline), respectively. Acute doses tested were 0.01, 0.09, and 0.9 mg/kg, SC fentanyl resulting in cumulative doses of 0.01, 0.1, and 1.0 mg/kg, SC fentanyl. Time course testing began 10 min after behavioral measurement of the highest cumulative dose. Time course assessments were performed at 10-min intervals for 60 min and then at 30-min intervals up to 120 min. “T X” indicates time in minutes following an injection of saline.