Learning-induced enduring changes in inhibitory synaptic transmission in lateral amygdala are mediated by p21-activated kinase

In this study we explored whether learning leads to enduring changes in inhibitory synaptic transmission in lateral amygdala (LA). We revealed that olfactory discrimination (OD) learning in rats led to a long-lasting increase in postsynaptic GABA_A channel-mediated miniature inhibitory postsynaptic currents (mIPSCs) in LA. Olfactory fear conditioning, but not auditory fear conditioning, also led to enduring enhancement in GABA_A-mediated mIPSCs. Auditory fear conditioning, but not olfactory fear conditioning or OD learning, induced an enduring reduction in the frequency but not the current of mIPSC events. We found that p21-activated kinase (PAK) activity is needed to maintain OD and olfactory fear conditioning learning-induced enduring enhancement of mIPSCs. Further analysis revealed that OD led to an increase in GABA_A channel conductance whereas olfactory fear conditioning increased the number of GABA_A channels. These alterations in GABA_A channels conductance and level are controlled by PAK activity. Our study shows that the learning-induced increase in postsynaptic inhibitory transmission in LA is specific to the sensory modality. However, the mechanism that mediates the increase in inhibitory transmission, namely the increase in the conductance or in the level of GABA_A channel, is learning specific. NEW & NOTEWORTHY Here we studied whether learning leads to long-lasting alterations in inhibitory synaptic transmission in lateral amygdala (LA). We revealed that learning led to enduring changes in inhibitory synaptic transmission in LA that are affected by the sensory modality (auditory or olfaction) used during learning. However, the mechanism that mediated the changes in inhibitory transmission (alterations in GABA_A channel level or conductance) depended on the type of learning. These long-lasting alterations are maintained by p21-activated kinase.