Novel blockers of hyperpolarization-activated current with isoform selectivity in recombinant cells and native tissue |
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Authors: | Del Lungo Martina Melchiorre Michele Guandalini Luca Sartiani Laura Mugelli Alessandro Koncz Istvan Szel Tamas Varro Andras Romanelli Maria Novella Cerbai Elisabetta |
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Institution: | CIMMBA, Department of Pharmacology, University of Florence, Firenze, Italy Department of Pharmaceutical Sciences, University of Florence, Florence, Italy. |
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Abstract: | BACKGROUND AND PURPOSESelective hyperpolarization activated, cyclic nucleotide-gated channel (HCN) blockers represent an important therapeutic goal due to the wide distribution and multiple functions of these proteins, representing the molecular correlate of f- and h-current (If or Ih). Recently, new compounds able to block differentially the homomeric HCN isoforms expressed in HEK293 have been synthesized. In the present work, the electrophysiological and pharmacological properties of these new HCN blockers were characterized and their activities evaluated on native channels.EXPERIMENTAL APPROACHHEK293 cells expressing mHCN1, mHCN2 and hHCN4 isoforms were used to verify channel blockade. Selected compounds were tested on native guinea pig sinoatrial node cells and neurons from mouse dorsal root ganglion (DRG) by patch-clamp recordings and on dog Purkinje fibres by intracellular recordings.KEY RESULTSIn HEK293 cells, EC18 was found to be significantly selective for HCN4 and MEL57A for HCN1 at physiological membrane potential. When tested on guinea pig sinoatrial node cells, EC18 (10 µM) maintained its activity, reducing If by 67% at ?120 mV, while MEL57A (3 µM) reduced If by 18%. In contrast, in mouse DRG neurons, only MEL57A (30 and 100 µM) significantly reduced Ih by 60% at ?80 mV. In dog cardiac Purkinje fibres, EC18, but not MEL57A, reduced the amplitude and slowed the slope of the spontaneous diastolic depolarization.CONCLUSIONSOur results have identified novel and highly selective HCN isoform blockers, EC18 and MEL57A; the selectivity found in recombinant system was maintained in various tissues expressing different HCN isoforms. |
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Keywords: | HCN channels If current Ih current neuropathic pain bradycardic agents HCN isoforms selectivity |
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