Fig. 4.
Effects of TLR4 antagonism on the self-administration of sucrose pellets. a Timeline illustrating the experimental design. b Sucrose responding during the FR5 sessions was stable and robust before evaluating the effects of vehicle or naltrexone (15, 30, and 60 mg/ kg, ip) using a within-subject design (n = 6) on FR5 responding for sucrose pellets. c Acute administration of (+)-naltrexone failed to alter the number of lever responses (left) or the total sucrose consumed (right) compared with the vehicle treatment. Data are presented as the mean ± SEM number of active and inactive lever responses