A-85380 [3-(2(S)-azetidinylmethoxy) pyridine]: in vitro pharmacological properties of a novel, high affinity alpha 4 beta 2 nicotinic acetylcholine receptor ligand.
The in vitro pharmacological properties of a novel cholinergic channel ligand, A-85380 [3-(2(S)-azetidinylmethoxy)pyridine], were examined using tissue preparations that express different putative nAChR subtypes. In radioligand binding studies, A-85380 is shown to be a potent and selective ligand for the human alpha 4 beta 2 nAChR subtype (Ki = 0.05 + 0.01 nM) relative to the human alpha 7 (Ki = 148 +/- 13 nM) and the muscle alpha 1 beta 1 dg subtype expressed in Torpedo electroplax (Ki = 314 +/- 12 nM). The R-enantiomer of A-85380, A-159470, displays little enantioselectivity towards the alpha 4 beta 2 and alpha 1 beta 1 delta gamma subtypes but does not display 12-fold enantioselectivity towards the alpha 7 subtype (Ki = 1275 +/- 199 nM). (+)- and(-)-Epibatidine display similar potencies at the human human alpha 4 beta 2 (Ki = 0.04 +/- 0.02 nM and 0.07 +/- 0.02 nM, respectively), human alpha 7 (Ki = 16 +/- 2 nM and 22 +/- 3 nM, respectively) and muscle alpha 1 beta 1 delta gamma g (Ki = 2.5 +/- 0.9 nM and 5.7 +/- 1.0 nM, respectively) nAChRs. Functionally, A-85380 is a potent activator of cation efflux through the human alpha 4 beta 2 (EC50 = 0.7 +/- 0.1 microM) and ganglionic (EC50 = 0.8 +/- 0.09 microM) subtypes, effects that are attenuated by pretreatment with mecamylamine (10 microM). Further, A-85380 can activate (EC50 = 8.9 +/- 1.9 microM) currents through channels formed by injection of the human alpha 7 subunit into Xenopus oocytes, effects that are attenuated by pretreatment with the alpha 7 nAChR antagonist, methyllycaconitine (10 nM). In all cases, A-85380 is more potent than (-)-nicotine but less potent than (+/-)-epibatidine. In neurotransmitter release studies, A-85380 stimulates the release of dopamine with an EC 50 value of 0.003 +/- 0.001 microM which is equipotent to (+/-)-epibatidine, and 20-fold more potent than (-)-nicotine (EC50 = 0.04 +/- 0.009 microM). Thus, A-85380 displays a profile of robust activation of a number of nAChR subtypes with substantially less affinity for [125I] alpha-BgT sites than [3H](-)-cytisine sites, suggesting that it may serve as a more selective pharmacologic probe for the alpha 4 beta 2 subtype relative to the alpha 7 and alpha 1 beta 1 delta g nAChRs than (+/-)-epibatidine.
Sullivan
J P
JP
Pharmaceutical Products Division, Abbott Laboratories, Abbott Park, IL 60064-3500, USA.
Donnelly-Roberts
D
D
Briggs
C A
CA
Anderson
D J
DJ
Gopalakrishnan
M
M
Piattoni-Kaplan
M
M
Campbell
J E
JE
McKenna
D G
DG
Molinari
E
E
Hettinger
A M
AM
Garvey
D S
DS
Wasicak
J T
JT
Holladay
M W
MW
Williams
M
M
Arneric
S P
SP
D000818:Animals; D001384:Azetidines / Q000494:pharmacology*; D002412:Cations / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009538:Nicotine / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000187:drug effects*
C104288:A 85380; D001384:Azetidines; D002412:Cations; D011725:Pyridines; D011978:Receptors, Nicotinic; D009538:Nicotine; D004298:Dopamine