Journal
ELIFE
Volume 11, Issue -, Pages -Publisher
eLIFE SCIENCES PUBL LTD
DOI: 10.7554/eLife.75119
Keywords
pacemaker current; sinoatrial node; TMYX; pure bradycardic agents; cAMP antagonism; HCN channels; Other
Categories
Funding
- Le Ren Tang [CTE_INT18DDIFR_01]
Ask authors/readers for more resources
This study provides a detailed characterization of the effects and mechanism of action of Tongmai Yangxin (TMYX) on pacemaker cells. TMYX slows the spontaneous action potentials rate by reducing the diastolic phase and shifting the I-f activation curve through a reduction of cAMP-induced stimulation of pacemaker channels. TMYX acts by directly antagonizing the cAMP-induced allosteric modulation of the pacemaker channels.
Tongmai Yangxin (TMYX) is a complex compound of the Traditional Chinese Medicine (TCM) used to treat several cardiac rhythm disorders; however, no information regarding its mechanism of action is available. In this study we provide a detailed characterization of the effects of TMYX on the electrical activity of pacemaker cells and unravel its mechanism of action. Single-cell electrophysiology revealed that TMYX elicits a reversible and dose-dependent (2/6 mg/ml) slowing of spontaneous action potentials rate (-20.8/-50.2%) by a selective reduction of the diastolic phase (-50.1/-76.0%). This action is mediated by a negative shift of the I-f activation curve (-6.7/-11.9 mV) and is caused by a reduction of the cyclic adenosine monophosphate (cAMP)-induced stimulation of pacemaker channels. We provide evidence that TMYX acts by directly antagonizing the cAMP-induced allosteric modulation of the pacemaker channels. Noticeably, this mechanism functionally resembles the pharmacological actions of muscarinic stimulation or beta-blockers, but it does not require generalized changes in cytoplasmic cAMP levels thus ensuring a selective action on rate. In agreement with a competitive inhibition mechanism, TMYX exerts its maximal antagonistic action at submaximal cAMP concentrations and then progressively becomes less effective thus ensuring a full contribution of I-f to pacemaker rate during high metabolic demand and sympathetic stimulation.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available