Fig. 4.

Infusion of NASPM into the NAc core blocks the expression of PIT in obesity-prone rats without altering conditioned discrimination. A) The average rate of active lever responding above baseline during the first CS+ and CS− presentation of PIT testing following infusion. Obesity-prone rats showed robust PIT following Vehicle infusion (n = 11), with presentation of the CS+ but not the CS− eliciting increases in active lever responding (white bars). Infusion of CNQX (0.3μg/0.5μl/hemisphere; 2.58 mM; n = 8) did not alter the expression of PIT (gray bars), but infusion of NASPM (20μg/0.5μl/hemisphere; 83.35 mM; n = 8) blocked PIT by reducing responding during CS+ presentations to levels similar to responding during the CS− (black bars). B) Time-course of active lever responding. Following Vehicle infusion, CS+ presentation elicited an immediate increase in the average rate of active lever responding, whereas the CS− did not. CNQX infusion produced a slight delay in the onset of responding following CS+ presentation, but did not eliminate the expression of PIT. In contrast, NASPM infusion selectively blocked CS+ triggered active lever responding throughout the entire CS presentation period. C) Active lever responding during the ITI was similar across infusion conditions. D) Average food cup entries during CS+ and CS− presentation. Conditioned discrimination was unaffected by infusion conditions. Following Vehicle, CNQX, and NASPM infusions food cup entries were greater during CS+ vs. CS− presentation. Infusion placements are shown at the right; * = p < .05, CS + vs. CS−.