Protein Synthesis is Not Required for Extinction of Paired-Associate Odor Discriminations Sarah Linderman, Elizabeth Nguyen, and Gretchen Hanson Gotthard Randolph-Macon Woman’s College Lynchburg, VA 24503 Introduction Much research has shown that the administration of protein synthesis inhibitors blocks the formation of new fear memories (e.g., Nader, Schafe, & LeDoux, 2000). In fact, most of the research in this area has focused on the acquisition of fear responses or used tasks that required animals to respond under aversive conditions (e.g., Morris water maze; Meiri & Rosenblum, 1998). Additionally, most studies examining the effects of blocked protein synthesis have examined acquisition of a completely new response, rather than extinction of an already-established response (i.e., learning to stop making responses that no longer work). A small number of studies have begun to examine the effects of protein synthesis inhibition on extinction (Lattal & Abel, 2001; Suzuki, et al., 2004); however, the results have been mixed and have been conducted with aversive tasks only (e.g., fear conditioning and the water maze). The present studied used an appetitive paired- associate digging task (Bunsey & Eichenbaum, 1996) to examine the effects of a protein synthesis inhibitor (cycloheximide) on extinction in rats. Considering extinction is similar to acquisition in that it also involves new learning, it was hypothesized that protein synthesis inhibition would block extinction and produce continued high levels of responding during testing. Results Acquisition All rats included in the present analyses met acquisition criteria (i.e., two out of the last four training trials correct and at least 75% correct overall during training). Extinction A one-way ANOVA revealed no differences in preference scores for the Cycloheximide (M=.58, SD=.45) and Vehicle (M=.35, SD=.39) groups on the extinction trial, F(12)=.913, p>.05 (see Figure 3). Additionally, a one-sample t-test showed that the Cycloheximide group had a preference for the correct cup, t(6)=3.38, p=.015, while the Vehicle group showed a marginal preference for the correct cup, t(5)=2.24, p=.07 (see Figure 3). Retention A one-way ANOVA revealed no differences in preference scores for the Cycloheximide group (Test 1: M=.43, SD=.79; Test 2: M=.09, SD=.62; Test 3: M=-.37, SD=.75) and the Vehicle group (Test 1: M=.11, SD=.93; Test 2: M=.13, SD=.74; Test 3: M=.07, SD=.82) on Test 1: F(12)=.441, p>.05, Test 2: F(12)=.01, p>.05, or Test 3: F(12)=.99, p>.05 (see Figure 3). Additionally, a one-sample t-test revealed that the Cycloheximide group [Test 1: t(6)=1.44, p>.05; Test 2: t(6)=.37, p>.05; Test 3: t(6)=- 1.29, p>.05] and the Vehicle group [Test 1: Shaping (Day 1) One cup of unscented sand (two trials) Shaping (Day 2) Two cups of unscented sand (two trials) Shaping (Day 3) Two cups of unscented sand (six trials) Training (Day 4) Trained on two paired-associate odor discriminations (six trials per discrimination) Extinction (Day 5) Extinction trial for one odor discrimination (one trial) Testing (Day 6) Test Trial 1: Extinguished Odor Test Trial 2: Non-Extinguished Odor Test Trial 3: Extinguished Odor (Reminder Effect) Figure 1