Extinction of conditioned fear is thought to form a new memory. Last year, we showed that infusions of the protein synthesis inhibitor anisomycin into the lateral ventricle blocked long- but not short-term memory for extinction of auditory fear conditioning (SFN abstract, 2002), suggesting that protein synthesis is necessary for consolidation of extinction memory. Behavioral and electrophysiological data have shown that the ventro-medial prefrontal cortex (vmPFC) is not required for short-term memory of extinction but is necessary for the recall of extinction 24-hrs later (Milad & Quirk, 2002). In the present experiment, we tested if anisomycin injections in the vmPFC would have the same effect as intraventricular injections. On day 1, rats implanted with cannulas in the vmPFC were given 7 tone-shock conditioning trials. On day 2, they received micro-infusions of either ACSF vehicle or anisomycin (100 ug/0.75 ul) followed by 15 extinction tones. On day 3, additional extinction trials were given to test for...