Keeping Fear Alive

Norepinephrine is involved in memory consolidation and fear learning. These investigators used a rat model of fear conditioning (tone/footshock) to examine how norepinephrine affects the maintenance and exacerbation of fear memories.

One day after fear conditioning, rats received infusions, into the lateral nucleus of the amygdala, of the beta-adrenergic agonist isoproterenol or saline, either after reactivation of fear memories or without memory reactivation. Two days later, rats underwent memory extinction. In rats given isoproterenol plus memory reactivation, freezing (fear response) to the conditioned tone was enhanced, and fear memories became more resistant to extinction. Memory reactivation alone, or isoproterenol alone, did not affec…