CALCIUM-PERMEABLE AMPA RECEPTORS MEDIATE LONG-TERM POTENTIATION IN INTERNEURONS IN THE AMYGDALA

Fear conditioning is a paradigm that has been used as a model for emot ional learning in animals'. The cellular correlate of fear conditionin g is thought to be associative N-methyl-D-aspartate (NMDA) receptor-de pendent synaptic plasticity within the amygdala(1-3). Here we show tha t glutamatergic synaptic transmission to inhibitory interneurons in th e basolateral amygdala is mediated solely by lpha-amino-3-hydroxy-5-me thyl-4-isoxazolepropionic acid (AMPA) receptors. In contrast to AMPA r eceptors at inputs to pyramidal neurons, these receptors have an inwar dly rectifying current-voltage relationship, indicative of a high perm eability to calcium(4 5), Tetanic stimulation of inputs to interneuron s caused an immediate and sustained increase in the efficacy of these synapses. This potentiation required a rise in postsynaptic calcium, b ut was independent of NMDA receptor activation. The potentiation of ex citatory inputs to interneurons was reflected as an increase in the am plitude of the GABAA-mediated inhibitory synaptic current in pyramidal neurons. These results demonstrate that excitatory synapses onto inte rneurons within a fear conditioning circuit show NMDA-receptor indepen dent long-term potentiation. This plasticity might underlie the increa sed synchronization of activity between neurons in the basolateral amy gdala after fear conditioning(6).