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A central element of post-traumatic stress disorder and some phobias is an intense fear response to environmental stimuli (fear conditioning). These experimenters used an animal model to determine the molecular mechanisms involved in extinguishing contextual fear conditioning.
The researchers placed mice in a specific cage and gave them a single footshock, which evoked fear (i.e., freezing behavior); the fear response was extinguished after 6 days of re-exposure to the cage without a shock. During the first 3 days of extinction, researchers delivered (through microcannulas inserted in the dorsal hippocampus) substances that inhibited or induced activity of cyclin-dependent kinase 5 (Cdk5); this protein kinase phosphorylates synaptic proteins…