The involvement of the amygdala AMPA receptors in learning and memory

Extensive evidence suggests that the amygdala is involved in emotionally influenced memory. There are several views concerning how the amygdala might be involved in affectively influenced memory. One view is that the amygdala is the primary site of storage for aversively based memory. If the amygdala is the locus of memory storage then treatments that block processes mediating the induction or expression of changes underlying neuroplasticity should also block memory. Long term potentiation (LTP) is a leading candidate as a molecular mechanism for memory storage. Induction of LTP is mediated by the NMDA glutamate receptor while expression of LTP is mediated by the AMPA glutamate receptor. Recent evidence indicates that intra-amygdala infusions of NMDA or AMPA receptor antagonists impair acquisition and retention performance. The present experiments examined whether the effects of amygdala AMPA receptor blockade on retention performance in aversively motivated tasks is due to effects on mechanisms underlying memory storage or on other mechanisms underlying performance.; Chapters 2 and 3 report the effects of blockade of amygdala AMPA receptors in two aversively motivated learning tasks. Intra-amygdala infusion of the AMPA receptor antagonist CNQX impaired retention performance of shock-motivated escape training and spatial discrimination in a water maze. CNQX attenuated, but did not block, the effects of increased training in the shock-motivated escape training task.; The experiments in Chapters 4, 5 and 6 examined the effects of blockade of amygdala AMPA receptors on reactivity to footshock, locomotor activity and expression of fear. Intra-amygdala infusions of CNQX decreased reactivity to footshock. Previous exposure to footshock decreased locomotor activity in an open field. Intra-amygdala infusion of CNQX blocked the shock-induced decrease in locomotor activity. Intra-amygdala infusion of CNQX increased the amount of time spent on the open arms of an elevated plus maze, suggesting that CNQX may be anxiolytic.; The combined findings indicate that the amygdala AMPA receptors are not critically involved in the expression of retention of aversively motivated training, and suggest that the amygdala may mediate the fear component of memory.