Selective Neuromodulation of Medial Prefrontal Cortex Inputs to the Lateral Habenula by Norepinephrine
Due to the firing of lateral habenula neurons (LHb) biasing a negative perspective of the world, an increase in LHb activity has been implicated in causing depression. Inputs to the LHb from higher-level cognition areas are likely providing the necessary signals for the LHb to respond to aversive stimuli and subsequently increase in activity. Projections to the LHb from the medial prefrontal cortex (mPFC) that processes negative valence events, have been identified, but the functions and characteristics of mPFC inputs to LHb still remain unknown. Here, we have identified and characterized mPFC inputs to LHb to be excitatory, glutamatergic, and under selective neuromodulation by norepinephrine (NE). Inputs from two other brain regions that may be instructing the LHb to process aversive stimuli, the ventral tegmental area (VTA) and the lateral hypothalamic area (LHA), were not affected by the addition of NE. We therefore propose that the lack of effect by NE on both VTA and LHA inputs may be due to the activation of adrenergic receptors at mPFC terminals, but not at VTA or LHA terminals, facilitating increased glutamate release.