title: Functional nicotinic acetylcholine receptors containing α6 subunits are on GABAergic neuronal boutons adherent to ventral tegmental area dopamine neurons.
abstract: Diverse nicotinic acetylcholine receptor (nAChR) subtypes containing different subunit combinations can be placed on nerve terminals or soma/dendrites in the ventral tegmental area (VTA). nAChR α6 subunit message is abundant in the VTA, but α6*-nAChR cellular localization, function, pharmacology, and roles in cholinergic modulation of dopaminergic (DA) neurons within the VTA are not well understood. Here, we report evidence for α6β2*-nAChR expression on GABA neuronal boutons terminating on VTA DA neurons. α-Conotoxin (α-Ctx) MII labeling coupled with immunocytochemical staining localizes putative α6*-nAChRs to presynaptic GABAergic boutons on acutely dissociated, rat VTA DA neurons. Functionally, acetylcholine (ACh) induces increases in the frequency of bicuculline-, picrotoxin-, and 4-aminopyridine-sensitive miniature IPSCs (mIPSCs) mediated by GABA(A) receptors. These increases are abolished by α6*-nAChR-selective α-Ctx MII or α-Ctx PIA (1 nm) but not by α7 (10 nm methyllycaconitine) or α4* (1 μm dihydro-β-erythroidine)-nAChR-selective antagonists. ACh also fails to increase mIPSC frequency in VTA DA neurons prepared from nAChR β2 knock-out mice. Moreover, ACh induces an α-Ctx PIA-sensitive elevation in intraterminal Ca(2+) in synaptosomes prepared from the rat VTA. Subchronic exposure to 500 nm nicotine reduces ACh-induced GABA release onto the VTA DA neurons, as does 10 d of systemic nicotine exposure. Collectively, these results indicate that α6β2*-nAChRs are located on presynaptic GABAergic boutons within the VTA and modulate GABA release onto DA neurons. These presynaptic α6β2*-nAChRs likely play important roles in nicotinic modulation of DA neuronal activity.
authors.affiliation: Division of Neurology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013-4496, USA.
authors.forename: Kechun
authors.initials: K
authors.lastname: Yang
authors.forename: Lori
authors.initials: L
authors.lastname: Buhlman
authors.forename: Ghous M
authors.initials: GM
authors.lastname: Khan
authors.forename: Robert A
authors.initials: RA
authors.lastname: Nichols
authors.forename: Guozhang
authors.initials: G
authors.lastname: Jin
authors.forename: J Michael
authors.initials: JM
authors.lastname: McIntosh
authors.forename: Paul
authors.initials: P
authors.lastname: Whiteaker
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Lukas
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000157:Aconitine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002038:Bungarotoxins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020916:Conotoxins / Q000378:metabolism; D004079:Dihydro-beta-Erythroidine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology; D004347:Drug Interactions; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D005260:Female; D018682:GABA Agents / Q000494:pharmacology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000172:deficiency / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D017557:Ventral Tegmental Area / Q000166:cytology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D015761:4-Aminopyridine; D000109:Acetylcholine; D000157:Aconitine; D002038:Bungarotoxins; D002118:Calcium; D020916:Conotoxins; D004079:Dihydro-beta-Erythroidine; D004298:Dopamine; D018683:Excitatory Amino Acid Agents; D018682:GABA Agents; D005968:Glutamate Decarboxylase; D009538:Nicotine; D018733:Nicotinic Antagonists; D026902:Potassium Channel Blockers; D011978:Receptors, Nicotinic; D005680:gamma-Aminobutyric Acid; C104518:nicotinic receptor alpha6; C054634:methyllycaconitine; C401141:glutamate decarboxylase 2