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. 1996 May 1;16(9):3112–3122. doi: 10.1523/JNEUROSCI.16-09-03112.1996

Fig. 8.

Fig. 8.

Top, Mean ± SEM rates of lever-pressing per 3 hr test session under normal drug reinforcement conditions (Baseline) and after repeated substitution of CPP with either vehicle [CPP (VEH), striped bars] or with the CPP plus sulpiride combination (CPP + SUL, solid bars). All animals had received only response-contingent CPP before the first substitution test. Rates of lever-pressing changes according to whether CPP was substituted with vehicle or the CPP plus sulpiride combination (F(8,80) = 4.82; p < 0.001). Within-group response rates were lower than those seen on the final day of baseline testing during substitution sessions 3 and 4 when the animals were tested repeatedly with vehicle, but the rates did not change when animals were tested repeatedly with the CPP plus sulpiride combination. During reversal session, the response rates of animals with previous experience with vehicle were not different from baseline, indicating no transfer between the vehicle and CPP plus sulpiride conditions. Significant differences (Tukey’s tests) are indicated as follows: *p < 0.05 versus CPP (vehicle), baseline session 4; ++p < 0.01 versus CPP (plus sulpiride), baseline session 4. Bottom, Response records for representative animals first trained to lever press for response-contingent CPP, and then tested repeatedly with either vehicle or the combination of CPP plus sulpiride. The first three records are from a representative animal (C247) tested repeatedly with vehicle; the first record represents baseline lever-pressing rates for response contingent CPP, whereas the second and the third records represent lever-pressing rates during the first and fourth substitution with vehicle. The last three records are from a representative animal (C244) tested repeatedly with the combination of CPP plus sulpiride; the fourth record represents baseline response lever-pressing rates for response-contingent CPP, whereas the fifth and sixth records represent lever-pressing rates during the first and fourth substitution with the combination of CPP plus sulpiride.