Figure 1.

Influence of NMDA antagonist infusion into nucleus accumbens core on acquisition of lever-pressing for sucrose pellets. Animals received intra-accumbens infusion of AP-5 (5 nmol) or vehicle (saline) on the first four test days; on the remaining training days, no infusion was given except on day 10, when all animals (including those previously infused with vehicle) were infused with AP-5. (A) Lever presses. In addition to treatment effect ∗∗, there were significant day × treatment ††, [F(8,112) = 4.7, P < 0.001], lever × treatment [F(1,14) = 17.6, P < 0.001], and day x lever x treatment [F(8,-112) = 3.9, P < 0.001] interactions, when all 9 days were analyzed. See text for further differences between groups. Also note that a separate ANOVA of days 3 and 4 (when animals were still receiving treatment) revealed a significant treatment effect {[F(1,14) = 7.1, P < 0.01], day × treatment interaction [F(1,14) = 13.4, P < 0.01], lever × treatment interaction [F(1,14) = 16.7, P < 0.001], and day × lever × treatment interaction [F(1,14) = 18.9, P < 0.001]}. These interactions indicate that on these days, control animals were beginning to learn to lever-press and to discriminate between correct and incorrect levers, whereas the AP-5 treated rats were not. Inc, incorrect responses. (B) Nose-pokes into food tray during learning. ∗∗, Significant effect of treatment; ††, day × treatment interaction, P < 0.01.