Pavlovian threat conditioning is a behavioral paradigm that has been successfully utilized to define the mechanisms underlying threat (fear) memory formation. The amygdala is a temporal lobe structure required for the acquisition, consolidation, and expression of threat (fear) memories. In particular, the lateral nucleus of the amygdala (LA) is the major input structure of the amygdala and is required for all aspects of threat learning and memory. The LA expresses many neurotransmitter and neuromodulator receptors. This chapter covers the molecular mechanisms that occur downstream of these receptors and how they influence LA-dependent Pavlovian threat learning.