Extracellular ATP neurotransmission and nicotine sex-specifically modulate habenular neuronal activity in adolescence

The recent increase in the use of nicotine products by teenagers has revealed an urgent need to better understand the impact of nicotine on the adolescent brain. Here, we sought to examine the actions of extracellular adenosine triphosphate (ATP) as a neurotransmitter and to investigate whether ATP and nicotinic signaling interact during adolescence. With the GRABATP sensor, we first demonstrated that nicotine induces extracellular ATP release in the medial habenula (MHb), a brain region involved in nicotine aversion and withdrawal. Using patch clamp electrophysiology, we then demonstrated that activation of the ATP receptors, P2X or P2Y1, increases the neuronal firing of cholinergic neurons. Surprisingly, contrasting interactive effects were observed with nicotine exposure. For the P2X receptor, activation had no observable effect on acute nicotine-mediated activity, but during abstinence after ten days of nicotine exposure, co-exposure to nicotine and the P2X agonist potentiated neuronal activity in female, but not male, neurons. For P2Y1 signaling, a potentiated effect of the agonist and nicotine was observed with acute exposure, but not following extended nicotine exposure. These data reveal a complex interactive effect between nicotinic and ATP signaling in the adolescent brain and provide mechanistic insights into extracellular ATP signaling with sex-specific alterations of neuronal responses based on prior drug exposure.