title: The nicotinic alpha 4 beta 2 receptor selective agonist, TC-2559, increases dopamine neuronal activity in the ventral tegmental area of rat midbrain slices.
abstract: The ability of alpha4beta2 nicotinic acetylcholine receptors to modulate dopaminergic (DA) cell activity in the ventral tegmental area (VTA) in rat midbrain slices was assessed using a selective alpha4beta2 receptor agonist, TC-2559 ((E)-N-methyl-4-[3-(5-ethoxypyridin)y1]-3-buten-1-amine). The selectivity of TC-2559 was characterized across 6 recombinant human nicotinic receptors (alpha4beta2, alpha2beta4, alpha4beta4, alpha3beta4, alpha3beta2 and alpha7) stably expressed in mammalian cell lines. Using a fluorescent imaging plate reader and fluo-3 to monitor changes in intracellular calcium, TC-2559 was found to be at least 69 fold more potent on alpha4beta2 than on other heteromeric subtypes, with an efficacy of 33%. No activity on the homomeric alpha7 subtype was detected. TC-2559 also showed selectivity for alpha4beta2 over the alpha4beta4 and alpha7 subtypes expressed in Xenopus oocytes. When bath applied to VTA slices, TC-2559 increased the firing of DA cells in a dose-dependent manner, in the same concentration range that activates alpha4beta2 receptors in recombinant cell lines or oocytes. The effect of TC-2559 was blocked by 2 microM dihydro-beta-erythroidine (an alpha4beta2-preferring antagonist), but not by 10 nM methyllycaconitine (an alpha7 antagonist). Glutamate receptor antagonists (6-cyano-7-nitroquinoxaline-2,3-dione and D(-)-2-amino-5-phosphonopentanoic acid) did not reduce TC-2559-induced responses, suggesting that the increase in DA cell firing induced by TC-2559 is caused by direct postsynaptic depolarisation via the activation of alpha4beta2 receptors and not by enhancement of glutamate release.
authors.affiliation: Lilly Research Centre, Eli Lilly & Co. Ltd, Erl Wood Manor, Sunninghill Road, Surrey GU20 6PH, Windlesham, UK. Chen_Ying_Dr@lilly.com
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.forename: Thomas J W
authors.initials: TJ
authors.lastname: Sharples
authors.forename: Keith G
authors.initials: KG
authors.lastname: Phillips
authors.forename: Giovanni
authors.initials: G
authors.lastname: Benedetti
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Broad
authors.forename: Ruud
authors.initials: R
authors.lastname: Zwart
authors.forename: Emanuele
authors.initials: E
authors.lastname: Sher
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002460:Cell Line; D004298:Dopamine / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008636:Mesencephalon / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018722:Nicotinic Agonists / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000502:physiology*; D017557:Ventral Tegmental Area / Q000187:drug effects* / Q000502:physiology; D014982:Xenopus laevis
chemical_list: D018722:Nicotinic Agonists; D011725:Pyridines; D011978:Receptors, Nicotinic; C419442:TC 2559; C403531:nicotinic receptor alpha4beta2; D004298:Dopamine