The medial habenula (MHb) is the less explored subregion of the emerging brain structure, Habenula (Hb) with roles in fear memory expression, anxiety, and addiction. At the neuron terminals where MHb neurons project to, the interpeduncular nucleus (IPN), vesicular neurotransmitter release is triggered by the influx of calcium ions via Ca v2.3 calcium channels, and robustly potentiated by GABAB …