Acquisition of fear conditioning in rats requires the synthesis of mRNA inthe amygdala

In this study, the role of mRNA synthesis in the amygdala was studied durin g the acquisition of conditional fear. Rats with cannulas placed in the bas olateral region of the amygdala were trained with a series of noise-shock p airings in a distinctive observation chamber. One half of the rats were pre treated with the mRNA synthesis inhibitor actinomycin-D (act-D). Responding to the training context and the auditory stimulus in a novel context measu red by defensive freezing was assessed. Pretreatment with act-D significant ly attenuated fear responses to both stimuli. Animals receiving act-D injec tions exhibited normal reactions to the conditioned stimulus-unconditioned stimulus pairings in the initial training session and displayed normal lear ning when retrained 7 days after injections. These results indicate that th e transcription of new mRNA and subsequent protein synthesis in the amygdal a may be essential for neural plasticity during this form of associative le arning.