Figure 1.

Experimental paradigms. The odor recognition task timeline and paradigm. Infusions were given 20 min prior to the familiarization trial (Trial 1) for all sessions (vehicle, NE antagonist cocktail, or a dosage of NE). For sessions where stressors were implemented, the stressor source (lamp for bright light or speaker for sound) was located adjacent to the testing chamber in the position shown in the figure during the entire odor exposure during Trial 1. For each trial, two inverted weigh dishes were placed on the top of the lid, in the far back corners. For Trial 1, as shown by an overhead view, the familiarization odor, “odor 1,” is pipetted onto a one inch square kim wipe into each of two weigh dishes. Between Trials 1 and 2, a variable intertrial interval is implemented (30, 60, 120, 180 min, depending on the particular experiment). For the Trial 2, odor 1 is placed in one weigh dish and a novel odor, “odor 2,” chemically and perceptually dissimilar from odor 1 is placed in a second weigh dish. The two dishes are placed in a randomized orientation. For each trial, investigation is defined as the rat's nose being within 1 cm of the weigh boat (white box in Trial 1, where each arrow is 1 cm). Memory is defined as significantly more investigation of odor 2 compared to odor 1. Additionally, note the quadrant markings at the base of cage in the photo of Trial 1 that were used for transitions in video scoring.