Impairment of object recognition memory by rapamycin inhibition of mTOR in the amygdala or hippocampus around the time of learning or reactivation

The role of the basolateral complex of the amygdala (BLA) in recognition memory remains poorly understood. The mammalian target of rapamycin (mTOR) in the BLA and other brain areas has been implicated in synaptic plasticity and memory. We have recently shown that mTOR signaling in both the BLA and the dorsal hippocampus (DH) is required for formation and reconsolidation of inhibitory avoidance, a fear-motivated memory task. Here we examined the effects of infusions of the mTOR inhibitor rapamycin into the BLA before or after either training or reactivation on retention of novel object recognition (NOR) memory in rats, and compared the effects with those obtained using intra-DH infusions. Male Wistar rats received bilateral infusions of vehicle or rapamycin into the BLA or DH before or after NOR training or reactivation. Rapamycin impaired NOR retention tested 24 h after training when given either before or immediately after training into the BLA or DH. Rapamycin also impaired retention measured 24 h after reactivation when infused before reactivation into the BLA or DH, or immediately after reactivation into the BLA, but not when given 6 h after reactivation into either the BLA or DH. The results suggest that mTOR signaling in the BLA and DH is involved in NOR memory formation and stabilization.

► Rapamycin impaired recognition memory when infused into the amygdala or hippocampus.
► Memory was also impaired by rapamycin given around the time of reactivation.
► mTOR in the amygdala and hippocampus regulates formation and stabilization of recognition memory.