Fig. 6.
Effects of increased lever–response requirements on the self-infusion of the SKF+Quin mixture into the ACB shell. Rats (n = 10) were given the opportunity to self-administer the mixture of 0.5 mm SKF plus 0.5 mm Quin over two sessions. As shown in A, rats exhibited a higher level of lever responses under the FR3 schedule than under the FR1 schedule with the levers collapsed together [F(1,9) = 8.19; p = 0.02]; rats also exhibited a reliable lever preference for the infusion lever over the control lever with the schedules collapsed together [F(1,9) = 6.24;p = 0.03]; and the lever × FR schedule interaction was not reliable [F(1,9) = 2.56]. There was no reliable difference between the schedules in the number of infusions [B; t(9) = 1.47] or in the time needed to complete the session [C;t(9) = 1.90]. Data are the mean ± SEM.