کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2192086 1097880 2007 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Modulation of rate by autonomic agonists in SAN cells involves changes in diastolic depolarization and the pacemaker current
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی بیولوژی سلول
پیش نمایش صفحه اول مقاله
Modulation of rate by autonomic agonists in SAN cells involves changes in diastolic depolarization and the pacemaker current
چکیده انگلیسی

Two distinct intracellular mechanisms have been proposed to affect the firing rate of cardiac pacemaker cells: one involves modulation of the If current by the second messenger cAMP, and one relies upon disruption or alteration of SR Ca2+ transients during activity. Although both mechanisms are necessary for proper automaticity and autonomic rate control, the specific contribution of each to pacemaking is still debated. We investigated if the two processes can be separated based on potentially different effects on action potential characteristics during rate modulation. To identify specific If-mediated effects, we used the selective If blocker ivabradine and found that ivabradine (3 μM) slows rate (− 16.2%) by selectively reducing (− 31.9%) the steepness of early diastolic depolarization (EDD). On the other hand ryanodine (3 μM), used to evaluate the effects of abolishment of SR Ca2+ transients, slowed rate (− 31.3%) by depolarizing the take-off potential (TOP, 18.1%) without affecting EDD. We therefore used these two parameters to identify If-based or SR Ca2+ transients-based processes and analyzed the effects on action potential's characteristics of Rp-cAMPs (50 μM), a membrane permeable cAMP analogue directly activating f-channels; we found that Rp-cAMPs accelerates rate by increasing EDD (+ 42.3%) without modifying TOP. Finally, rate modulation was achieved by muscarinic (ACh 0.01 μM) or β-adrenergic (Iso 1 μM) stimulation; in both cases, rate changes were associated with modifications of EDD (ACh, − 29.3% and Iso, + 47.6%) and not of TOP. We conclude that rate-related changes in the EDD induced by autonomic agonists are mediated by If and not by processes involving SR Ca2+ transients.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular and Cellular Cardiology - Volume 43, Issue 1, July 2007, Pages 39–48
نویسندگان
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