Jehl, J. | Search bioRxiv

bioRxiv2023

The interpeduncular nucleus blunts the rewarding effect of nicotine

Nicotine, by stimulating ventral tegmental area (VTA) dopaminergic neurons, has a rewarding effect that drives tobacco consumption. In turn, the interpeduncular nucleus (IPN) is thought to become activated at high nicotine doses to restrict drug intake. However, the dynamics of the IPN response to nicotine and its impact on the rewarding effect of the drug remain unknown. To address this issue, we have developed a genetically-modified mouse model, in which a "suicide" antagonist of nicotinic acetylcholine receptors (nAChRs) selectively attaches to a designer {beta}4 nAChR subunit. By locally infusing this antagonist in the IPN, we achieved pharmacologically-specific and sustained antagonism of nAChRs containing the {beta}4 subunit. By combining this chemogenetic method with in vivo electrophysiology, we show that even at low doses, nicotine activates and inhibits two different populations of IPN neurons, and that {beta}4-containing nAChRs are only involved in the activation response. Furthermore, blocking the response to nicotine selectively in the IPN increased both the sensitivity of the VTA to the drug and its rewarding effect in a conditioned place preference paradigm. These findings indicate that the IPN is engaged across a large range of nicotine doses and acts as a regulatory brake on the nicotine reward circuit.

neuroscience↗

bioRxiv2021

Prolonged nicotine exposure reduces aversion to the drug in mice by altering nicotinic transmission in the interpeduncular nucleus.

Nicotine intake is likely to result from a balance between the rewarding and aversive properties of the drug, yet the individual differences in neural activity that control aversion to nicotine and their adaptation during the addiction process remain largely unknown. Using a two-bottle choice experiment, we observed a high heterogeneity in nicotine-drinking profiles in isogenic adult male mice, with about half of the mice persisting in consuming nicotine even at high concentrations, whereas the other half stopped consuming. We found that nicotine intake was negatively correlated with nicotine-evoked currents in the interpeduncular nucleus (IPN), and that prolonged exposure to nicotine, by weakening this response, decreased aversion to the drug, and hence boosted consumption. Lastly, using knock-out mice and local gene re-expression, we identified {beta}4-containing nicotinic acetylcholine receptors of IPN neurons as the molecular and cellular correlates of nicotine aversion. Collectively, our results identify the IPN as a substrate of individual variabilities and adaptations in nicotine consumption.

neuroscience↗