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Nicotine aversion is mediated by GABAergic interpeduncular nucleus inputs to laterodorsal tegmentum.

ABSTRACT: Nicotine use can lead to dependence through complex processes that are regulated by both its rewarding and aversive effects. Recent studies show that aversive nicotine doses activate excitatory inputs to the interpeduncular nucleus (IPN) from the medial habenula (MHb), but the downstream targets of the IPN that mediate aversion are unknown. Here we show that IPN projections to the laterodorsal tegmentum (LDTg) are GABAergic using optogenetics in tissue slices from mouse brain. Selective stimulation of these IPN axon terminals in LDTg in vivo elicits avoidance behavior, suggesting that these projections contribute to aversion. Nicotine modulates these synapses in a concentration-dependent manner, with strong enhancement only seen at higher concentrations that elicit aversive responses in behavioral tests. Optogenetic inhibition of the IPN-LDTg connection blocks nicotine conditioned place aversion, suggesting that the IPN-LDTg connection is a critical part of the circuitry that mediates the aversive effects of nicotine.

SUBMITTER: Wolfman SL

PROVIDER: S-EPMC6045623 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Nicotine aversion is mediated by GABAergic interpeduncular nucleus inputs to laterodorsal tegmentum.

Wolfman Shannon L SL Gill Daniel F DF Bogdanic Fili F Long Katie K Al-Hasani Ream R McCall Jordan G JG Bruchas Michael R MR McGehee Daniel S DS

Nature communications 20180713 1

Nicotine use can lead to dependence through complex processes that are regulated by both its rewarding and aversive effects. Recent studies show that aversive nicotine doses activate excitatory inputs to the interpeduncular nucleus (IPN) from the medial habenula (MHb), but the downstream targets of the IPN that mediate aversion are unknown. Here we show that IPN projections to the laterodorsal tegmentum (LDTg) are GABAergic using optogenetics in tissue slices from mouse brain. Selective stimulat ...[more]

PMID: 30006624

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Project description:Allelic variation in CHRNA3, the gene encoding the α3 nicotinic acetylcholine receptor (nAChR) subunit, increases vulnerability to tobacco dependence and smoking-related diseases, but little is known about the role for α3-containing (α3*) nAChRs in regulating the addiction-related behavioral or physiological actions of nicotine. α3* nAChRs are densely expressed by medial habenula (mHb) neurons, which project almost exclusively to the interpeduncular nucleus (IPn) and are known to regulate nicotine avoidance behaviors. We found that Chrna3tm1.1Hwrt hypomorphic mice, which express constitutively low levels of α3* nAChRs, self-administer greater quantities of nicotine (0.4 mg kg-1 per infusion) than their wild-type littermates. Microinfusion of a lentivirus vector to express a short-hairpin RNA into the mHb or IPn to knock-down Chrna3 transcripts markedly increased nicotine self-administration behavior in rats (0.01-0.18 mg kg-1 per infusion). Using whole-cell recordings, we found that the α3β4* nAChR-selective antagonist α-conotoxin AuIB almost completely abolished nicotine-evoked currents in mHb neurons. By contrast, the α3β2* nAChR-selective antagonist α-conotoxin MII only partially attenuated these currents. Finally, micro-infusion of α-conotoxin AuIB (10 μm) but not α-conotoxin MII (10 μm) into the IPn in rats increased nicotine self-administration behavior. Together, these data suggest that α3β4* nAChRs regulate the stimulatory effects of nicotine on the mHb-IPn circuit and thereby regulate nicotine avoidance behaviors. These findings provide mechanistic insights into how CHRNA3 risk alleles can increase the risk of tobacco dependence and smoking-related diseases in human smokers.SIGNIFICANCE STATEMENT Allelic variation in CHRNA3, which encodes the α3 nicotinic acetylcholine receptor (nAChR) subunit gene, increases risk of tobacco dependence but underlying mechanisms are unclear. We report that Chrna3 hypomorphic mice consume greater quantities of nicotine than wild-type mice and that knock-down of Chrna3 gene transcripts in the habenula or interpeduncular nucleus (IPn) increases nicotine intake in rats. α-Conotoxin AuIB, a potent antagonist of the α3β4 nAChR subtype, reduced the stimulatory effects of nicotine on habenular neurons, and its infusion into the IPn increased nicotine intake in rats. These data suggest that α3β4 nAChRs in the habenula-IPn circuit regulate the motivational properties of nicotine.

Dataset Information

Nicotine aversion is mediated by GABAergic interpeduncular nucleus inputs to laterodorsal tegmentum.

Publications

Nicotine aversion is mediated by GABAergic interpeduncular nucleus inputs to laterodorsal tegmentum.

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