Figure 3.

Systemic administration of 10 mg/kg RGFP963 and 10 mg/kg RGFP966 does not nonspecifically affect extinction retention, motor, or exploratory behavior. (A) To test whether RGFP963 and RGFP966 nonspecifically affect extinction retention, subjects received 2 d of 10 CS–US pairings during fear conditioning in “Context A,” 3 CS trials during grouping, and 15 CS trials during extinction retention (all extinction tests were performed in “Context B”), however, only one group, “extinction” underwent a 30 CS trial extinction training between grouping and extinction retention tests. The following groups were tested: “home cage (HC),” “extinction,” “vehicle-no extinction,” “10 mg/kg RGFP963-no extinction,” “10 mg/kg RGFP966-no extinction” (n = 10/group). No significant differences were observed on extinction retention day 1 or extinction retention day 2. A significant effect of CS on freezing during extinction training in the “extinction group” was observed (P < 0.05), suggesting that within-session extinction was maintained, despite a lack of effect on extinction retention. These data suggest that extinction training consisting of 30 CS trials does not significantly diminish freezing after a relatively robust fear conditioning paradigm of 2 d of 10 CS–US pairings and that 10 mg/kg RGFP963 and RGFP966 does not nonspecifically enhance extinction retention. (B,C) Thirty minutes prior to testing, RGFP963 and RGFP966 were administered IP at a dose of 10 mg/kg. No significant effect of drug on time spent in the center (sec) or distance traveled (cm) was observed (n = 8/group).