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Galantamine is not a positive allosteric modulator of human α4β2 or α7 nicotinic acetylcholine receptors
Author(s) -
Kowal Natalia M,
Ahring Philip K,
Liao Vivian W Y,
Indurti Dinesh C,
Harvey Benjamin S,
O'Connor Susan M,
Chebib Mary,
Olafsdottir Elin S,
Balle Thomas
Publication year - 2018
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.14329
Subject(s) - galantamine , allosteric regulation , pharmacology , allosteric modulator , nicotinic agonist , chemistry , agonist , acetylcholine , acetylcholinesterase , receptor , acetylcholinesterase inhibitor , electrophysiology , acetylcholine receptor , neuroscience , medicine , biology , biochemistry , dementia , disease , enzyme , donepezil
Background and Purpose The alkaloid galantamine was originally isolated from the green snowdrop Galanthus woronowii and is currently marketed as a drug for treatment of mild to moderate dementia in patients with Alzheimer's disease. In addition to a well‐documented proficiency to inhibit acetylcholinesterase, galantamine has been reported to increase neuronal nicotinic ACh (nACh) receptor function by acting as a positive allosteric modulator. Yet there remains controversy regarding these findings in the literature. To resolve this conundrum, we evaluated galantamine actions at α4β2 and α7, which represent the nACh receptors most commonly associated with mammalian cognitive domains. Experimental Approach α4β2 [in (α4) 3 (β2) 2 and (α4) 2 (β2) 3 stoichiometries] and α7 nACh receptors were expressed in Xenopus laevis oocytes and subjected to two‐electrode voltage‐clamp electrophysiological experiments. Galantamine (10 nM to 100 μM) was evaluated for direct agonist effects and for positive modulation by co‐application with sub‐maximally efficacious concentrations of ACh. In addition, similar experiments were performed with α7 nACh receptors stably expressed in HEK293 cells using patch‐clamp electrophysiology. Key Results In concentrations ranging from 10 nM to 1 μM, galantamine did not display direct agonism nor positive modulatory effects at any receptor combination tested. At concentrations from 10 μM and above, galantamine inhibited the activity with a mechanism of action consistent with open‐channel pore blockade at all receptor types. Conclusion and Implications Based on our data, we conclude that galantamine is not a positive allosteric modulator of α7 or α4β2 receptors, which represent the majority of nACh receptors in mammalian brain.