Effects of MLA on trace fear conditioning in chronic saline and chronic nicotine treated mice. MLA (1.5, 3, 9 mg/kg) did not alter baseline, trace-interval, altered, or cued freezing in chronic saline (A) or chronic nicotine (B) treated mice. Thus, the low-affinity nAChR antagonist MLA failed to precipitate nicotine withdrawal-induced deficits in trace fear conditioning. Data are reported as mean ± standard error of the mean.