Figure 1.

Experimental design. Sated rats were tested for food consumption in the presence of CS+ or CS– in two consecutive tests (the order of tests was counterbalanced). The tests were arranged temporally to correlate with the peaks for nuclear mRNA induction of Arc and H1a. Each food-consumption test started with a pretest (5 min), immediately followed by test 1 (5 min). After the first test, animals were taken to the colony and 25 min later were brought back for test 2 (5 min). Immediately after the second test, rats were perfused. Thus, test 1, which occurred 35–30 min before the rats were killed, matches the peak of H1a nuclear mRNA induction, whereas test 2, which occurred 5 min before the rats were killed, matches the peak for Arc nuclear mRNA induction.