Figure 6.

CREST knockdown in the NAc core initially impairs the acquisition of a chain schedule in a rat self-administration model. A, B, Lever pressing behavior (A) and time to completion (B) during the final two sessions of take responding (Days 1 and 2), and the eight sessions of seek–take responding with increasing VI requirements on the seek lever (Days 3–10; see Materials and Methods). Anti-CREST and Control animals total lever presses were similar (A), but introduction of the seek–take chain schedule significantly increased the time to complete session with the introduction of the seek–take chain schedule (Days 3 and 4), which was attenuated with the increasing VI schedule (B). C, D, Cumulative lever press plots for Scrambled morpholino control (Control) and anti-CREST morpholino (Anti-CREST) animals. C, Control and anti-CREST groups displayed similar lever pressing frequency during the final day of the FR1 take procedure (Day 2; shaded region = SE; p > 0.1). D, An introduction of a seek–take chain schedule of reinforcement significantly reduced lever pressing frequency for the anti-CREST but not the Control group during the first day of seek–take training (Day 3). E, Representative Western blot comparing the expression of CREST protein (55 kDa) in Control and anti-CREST rats. F, CREST Protein was significantly knocked down in the anti-CREST group compared with Control. n = 5 for Control and n = 5 for anti-CREST. *p < 0.05, **p < 0.01.