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Characterization of the human HCN1 channel and its inhibition by capsazepine
Author(s) -
Gill Catherine H,
Randall Andrew,
Bates Stewart A,
Hill Kerstin,
Owen Davina,
Larkman Phil M,
Cairns William,
Yusaf Shahnaz P,
Murdock Paul R,
Strijbos Paul J L M,
Powell Andrew J,
Benham Christopher D,
Davies Ceri H
Publication year - 2004
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 - 10.1038/sj.bjp.0705945
Subject(s) - capsazepine , hyperpolarization (physics) , chemistry , cyclic nucleotide gated ion channel , biophysics , patch clamp , potassium channel , extracellular , intracellular , antagonist , membrane potential , reversal potential , inhibitory postsynaptic potential , biochemistry , receptor , transient receptor potential channel , cyclic nucleotide , stereochemistry , neuroscience , biology , nucleotide , trpv1 , nuclear magnetic resonance spectroscopy , gene
The human hyperpolarization‐activated cyclic nucleotide‐gated 1 (hHCN1) subunit was heterologously expressed in mammalian cell lines (CV‐1 and CHO) and its properties investigated using whole‐cell patch‐clamp recordings. Activation of this recombinant channel, by membrane hyperpolarization, generated a slowly activating, noninactivating inward current. The pharmacological properties of hHCN1‐mediated currents resembled those of native hyperpolarization‐activated currents ( I h ), that is, blockade by Cs + (99% at 5 m M ), ZD 7288 (98% at 100 μ M ) and zatebradine (92% at 10 μ M ). Inhibition of the hHCN1‐mediated current by ZD 7288 was apparently independent of prior channel activation (i.e. non‐use‐dependent), whereas that induced by zatebradine was use‐dependent. The VR1 receptor antagonist capsazepine inhibited hHCN1‐mediated currents in a concentration‐dependent (IC 50 =8 μ M ), reversible and apparently non‐use‐dependent manner. This inhibitory effect of capsazepine was voltage‐independent and associated with a leftward shift in the hHCN1 activation curve as well as a dramatic slowing of the kinetics of current activation. Elevation of intracellular cAMP or extracellular K + significantly enhanced aspects of hHCN1 currents. However, these manipulations did not significantly affect the capsazepine‐induced inhibition of hHCN1. The development of structural analogues of capsazepine may yield compounds that could selectively inhibit HCN channels and prove useful for the treatment of neurological disorders where a role for HCN channels has been described.British Journal of Pharmacology (2004) 143 , 411–421. doi: 10.1038/sj.bjp.0705945