title: Calcium mobilization elicited by two types of nicotinic acetylcholine receptors in mouse substantia nigra pars compacta.
abstract: Nicotinic acetylcholine receptors (nAChRs) are expressed in the midbrain ascending dopaminergic system, a target of many addictive drugs. Here we assessed the intracellular Ca2+ level by imaging fura-2-loaded cells in substantia nigra pars compacta in mouse brain slices, and we examined the influence on this level of prolonged exposures to nicotine using mice lacking the nAChR beta2-subunit. In control cells, superfusion with nicotine (10-100 microM) caused a long-lasting rise of intracellular Ca2+ level which depended on extracellular Ca2+. This nicotinic response was almost completely absent in beta2-/- mutant mice, leaving a small residual response to a high concentration (100 microM) of nicotine which was inhibited by the alpha7-subunit-selective antagonist, methyllycaconitine. Conversely, the alpha7-subunit-selective agonist choline (10 mM) caused a methyllycaconitine-sensitive increase in intracellular Ca2+ level both in wild-type and beta2-/- mutant mice. Nicotine-elicited Ca2+ mobilization was reduced by the Na+ channel blocker tetrodotoxin (TTX) and by T-type Ca2+ channel blocking agents, whereas the choline-elicited Ca2+ increase was insensitive to TTX. Neither nicotine nor choline produced Ca2+ increase following inhibition of the release of Ca2+ from intracellular stores by dantrolene. These results demonstrate that in nigral dopaminergic neurons, nicotine can elicit Ca2+ mobilization via activation of two distinct nAChR subtypes: that of beta2-subunit-containing nAChR followed by activation of Na+ channel and T-type Ca2+ channels, and/or activation of alpha7-subunit-containing nAChR. The Ca2+ influx due to nAChR activation is subsequently amplified by the recruitment of intracellular Ca2+ stores. This Ca2+ mobilization may possibly contribute to the long-term effects of nicotine on the dopaminergic system.
authors.affiliation: CNRS UA D1284 Neurobiologie Moleculaire, Institut Pasteur, Paris, France.
authors.forename: H
authors.initials: H
authors.lastname: Tsuneki
authors.forename: R
authors.initials: R
authors.lastname: Klink
authors.forename: C
authors.initials: C
authors.lastname: Léna
authors.forename: H
authors.initials: H
authors.lastname: Korn
authors.forename: J P
authors.initials: JP
authors.lastname: Changeux
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000157:Aconitine / Q000031:analogs & derivatives / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D002038:Bungarotoxins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002794:Choline / Q000494:pharmacology; D004079:Dihydro-beta-Erythroidine / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007306:Insecticides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009474:Neurons / Q000737:chemistry* / Q000201:enzymology; D009538:Nicotine / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D018697:Nootropic Agents / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011073:Polyamines / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000737:chemistry / Q000502:physiology; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*; D013378:Substantia Nigra / Q000166:cytology* / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis
chemical_list: D001565:Benzoates; D002038:Bungarotoxins; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; C102391:FTX 3.3; D005456:Fluorescent Dyes; D007211:Indoles; D007306:Insecticides; D018722:Nicotinic Agonists; D018697:Nootropic Agents; D011073:Polyamines; D011978:Receptors, Nicotinic; C403531:nicotinic receptor alpha4beta2; C079694:alpha-methyl-4-carboxyphenylglycine; C054634:methyllycaconitine; D004079:Dihydro-beta-Erythroidine; D013779:Tetrodotoxin; D009538:Nicotine; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D014446:Tyrosine 3-Monooxygenase; D009543:Nifedipine; D002794:Choline; D002118:Calcium; D005998:Glycine; D016257:Fura-2; D000157:Aconitine; C000543:cyclopiazonic acid