Figure 5.

ERK activation in the NAcc is increased during tests for pavlovian-instrumental transfer and conditioned approach. Rats that underwent pavlovian and instrumental training paradigms were tested for pavlovian-instrumental transfer (n = 7) or conditioned food cup approach (n = 6). These tests were identical, except for the availability of the instrumental levers during the pavlovian-instrumental transfer test but not the conditioned approach test. After the respective tests, pERK1/2 staining in the NAcc was assessed. A, Animals tested for conditioned approach (left set of bars) showed greater food-cup approach during tone presentations compared with the pretone period. Animals tested for pavlovian-instrumental transfer (right set of bars) showed greater responding on the active lever during tone presentations compared with the pretone period. B, Significantly more pERK1/2-positive neurons were observed in the NAcc of rats that underwent the conditioned approach or the pavlovian-instrumental transfer test compared with a control group (n = 7) that received unrewarded tones during training. C–E, Representative photomicrographs of pERK-stained cells in the NAcc from a control animal (C), an animal that underwent the conditioned approach test (D), and an animal that underwent the pavlovian-instrumental transfer test (E). *Significantly different from pretone responding; **significantly different from the control group, all at p < 0.05. All data are represented as mean ± SEM.