Heterosynaptic Long-Term Potentiation of Inhibitory Interneurons in the Lateral Amygdala

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Abstract
Long-term potentiation (LTP) of synaptic transmission in the lateral amygdala (LA) is believed to underlie the formation and retention of fear memories. To explore the role of inhibitory transmission in amygdala plasticity, we recorded from LA inhibitory interneurons in vitro before and after tetanization of the thalamo-LA pathway, one of the major inputs to LA involved in fear learning. Tetanization resulted in LTP of the EPSPs elicited in both the tetanized thalamic pathway and the untetanized cortical pathway to LA. This LTP was NMDA-dependent and associated with a decrease in paired-pulse facilitation in both pathways. In LA excitatory cells, LTP of interneurons resulted in an increase in the amplitude of GABAergic IPSPs in both input pathways. Finally, isolated GABAergic IPSPs between inhibitory and excitatory neurons could be potentiated as well. Plasticity of inhibitory transmission within the LA may therefore contribute significantly to LA-mediated functions, such as fear conditioning.