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Inhibitory effects of sevoflurane on pacemaking activity of sinoatrial node cells in guinea‐pig heart
Author(s) -
Kojima Akiko,
Kitagawa Hirotoshi,
OmatsuKanbe Mariko,
Matsuura Hiroshi,
Nosaka Shuichi
Publication year - 2012
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/j.1476-5381.2012.01914.x
Subject(s) - sinoatrial node , guinea pig , inhibitory postsynaptic potential , medicine , neuroscience , heart rate , pharmacology , cardiology , chemistry , biology , blood pressure
BACKGROUND AND PURPOSE The volatile anaesthetic sevoflurane affects heart rate in clinical settings. The present study investigated the effect of sevoflurane on sinoatrial (SA) node automaticity and its underlying ionic mechanisms. EXPERIMENTAL APPROACH Spontaneous action potentials and four ionic currents fundamental for pacemaking, namely, the hyperpolarization‐activated cation current ( I f ), T‐type and L‐type Ca 2+ currents ( I Ca,T and I Ca,L , respectively), and slowly activating delayed rectifier K + current ( I Ks ), were recorded in isolated guinea‐pig SA node cells using perforated and conventional whole‐cell patch‐clamp techniques. Heart rate in guinea‐pigs was recorded ex vivo in Langendorff mode and in vivo during sevoflurane inhalation. KEY RESULTS In isolated SA node cells, sevoflurane (0.12–0.71 mM) reduced the firing rate of spontaneous action potentials and its electrical basis, diastolic depolarization rate, in a qualitatively similar concentration‐dependent manner. Sevoflurane (0.44 mM) reduced spontaneous firing rate by approximately 25% and decreased I f , I Ca,T , I Ca,L and I Ks by 14.4, 31.3, 30.3 and 37.1%, respectively, without significantly affecting voltage dependence of current activation. The negative chronotropic effect of sevoflurane was partly reproduced by a computer simulation of SA node cell electrophysiology. Sevoflurane reduced heart rate in Langendorff‐perfused hearts, but not in vivo during sevoflurane inhalation in guinea‐pigs. CONCLUSIONS AND IMPLICATIONS Sevoflurane at clinically relevant concentrations slowed diastolic depolarization and thereby reduced pacemaking activity in SA node cells, at least partly due to its inhibitory effect on I f , I Ca,T and I Ca,L . These findings provide an important electrophysiological basis of alterations in heart rate during sevoflurane anaesthesia in clinical settings.