Dihydropyridine inhibition of the glycine receptor: Subunit selectivity and a molecular determinant of inhibition

NEUROPHARMACOLOGY

卷:56

Article

Chen, Xuebin^1,2  Cromer, Brett^3,4  Webb, Timothy I.^1,2  Yang, Zhe^1,2  Hantke, Janina⁵  Harvey, Robert J.⁵  Parker, Michael W.⁶  Lynch, Joseph W.^1,2 

[1] Univ Queensland, Sch Biomed Sci, Brisbane, Qld 4072, Australia

[2] Univ Queensland, Queensland Brain Inst, Brisbane, Qld 4072, Australia

[3] Univ Melbourne, Howard Florey Inst, Parkville, Vic 3010, Australia

[4] Univ Melbourne, Dept Pharmacol, Parkville, Vic 3010, Australia

[5] Univ London, Sch Pharm, Dept Pharmacol, London WC1N 1AX, England

[6] St Vincents Inst Med Res, Fitzroy, Vic 3065, Australia

关键词: Nifedipine;    Nicardipine;    Cys-loop receptor;    Chloride channel;    Inhibitory neurotransmission;    Binding site;   

DOI  :  10.1016/j.neuropharm.2008.07.001

来源: Elsevier

【 摘 要 】

The dihydropyridines (DHPs), nifedipine and nicardipine, modulate native glycine receptors (GlyRs) at micromolar concentrations. Nicardipine has a biphasic potentiating and inhibitory effect, whereas nifedipine causes inhibition only. The present study sought to investigate (1) the molecular mechanism by which these compounds inhibit recombinant GlyRs, and (2) their potential utility as subunit-selective inhibitors of alpha 1, alpha 1 beta, alpha 3 and alpha 3 beta GlyRs. The rate of onset of inhibition in the open state was accelerated by pre-application of DHP in the closed state, with the degree of acceleration proportional to the concentration of pre-applied DHP This implies a non-inhibitory binding site close to the DHP inhibitory site. DHP inhibition was use-dependent and independent of glycine concentration, consistent with a pore-blocking mode of action. DHP sensitivity was abolished by the G2'A mutation, providing a strong case for a DHP binding site in the pore. Nifedipine exhibited an approximately 10-fold higher inhibitory potency at alpha-containing relative to alpha 3-containing receptors, whereas nicardipine was only weakly selective for alpha 1-containing GlyRs. The differential sensitivities of nifedipine and nicardipine for different GlyR isoforms suggest that DHPs may be a useful resource to screen as pharmacological tools for selectively inhibiting different synaptic GlyR isoforms. (C) 2008 Elsevier Ltd. All rights reserved.

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