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Muscarinic potassium channels play a significant role in the negative chronotropic response with or without background sympathetic tone
Author(s) -
Mizuno Masaki,
Kamiya Atsunori,
Kawada Toru,
Sugimachi Masaru
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.970.2
Subject(s) - chronotropic , medicine , muscarinic acetylcholine receptor , endocrinology , vagotomy , stimulation , potassium channel , atropine , acetylcholine , heart rate , tonic (physiology) , chemistry , anesthesia , blood pressure , receptor
Although a larger decrease in the steady‐state heart rate (HR) in response to more potent tonic vagal stimulation (VS) is mediated by the muscarinic potassium (K ACh ) channels, the effect of background sympathetic tone on the contribution of the K ACh channels to the negative chronotropic response remains to be elucidated. In anesthetized rabbits with sinoaortic denervation and vagotomy, we examined the HR response to stepwise vagal stimulation (VS) (5, 10, 15 and 20 Hz). A selective K ACh channel blocker tertiapin attenuated the HR decrease to less than half of that observed under control condition. A concomitant tonic cardiac sympathetic stimulation (5 Hz) significantly augmented the HR reduction both in control (91±16 to 130±27 bpm, @20Hz VS, mean±SD, P<0.01) and tertiapin (30±12 to 67±13 bpm, P<0.01) condition. The contribution of K ACh channels, assessed by the attenuation of the HR reduction, was 60±24 and 63±17 bpm in the absence and the presence of background sympathetic tone, respectively. In conclusion, muscarinic potassium channels play a significant role in the negative chronotropic response with or without background sympathetic tone.