α-linolenic acid-induced facilitation of GABAergic synaptic transmission is mediated via acid-sensing ion channel (ASIC1a) activity in the basolateral amygdala

Epilepsy affects more than 70 million people worldwide. A seizure focus that develops in different cortical brain regions can present as either focal or generalized seizures. Temporal lobe epilepsy is a highly pharmacoresistant form of epilepsy that involves the amygdala, hippocampus with or without hippocampal sclerosis as well as other limbic structures. Loss and/or dysfunction of GABAergic inhibitory neurons play a critical role in tipping the balance toward excitation. Synchronous burst firing is a feature of inhibitory neurons that is thought to regulate and rectify large excitatory neuronal networks in the BLA and is thought to underlie higher cognitive function. Acid sensing ion channels (ASIC) activated by decreases in pH, the presence of ammonium ion or a slight lowering of temperature are present on excitatory and inhibitory neurons and can alter excitability. The net effect of the activation of ASIC1a channels in the BLA is inhibition. ASIC1a channels are active in the basal state, enhancing primarily GABAergic inhibition by direct depolarization of interneurons but also by indirect excitation of interneurons via ASIC1a-mediated depolarization of pyramidal neurons. In this study, we examine the contribution of ASIC1a channel activation on alpha-linolenic acid (ALA)-induced GABAergic inhibitory synchronous burst firing in the BLA. Our results show that ALA initiates inhibitory bursts that are dependent, in part, on the activation of ASIC1a channels that may in turn be mediated by mature brain-derived neurotrophic factor.