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Muscarinic inhibitory and stimulatory regulation of the L‐type Ca 2+ current is not altered in cardiac ventricular myocytes from mice lacking endothelial nitric oxide synthase
Author(s) -
Belevych Andriy E.,
Harvey Robert D.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00279.x
Subject(s) - medicine , endocrinology , myocyte , acetylcholine , isoprenaline , nitric oxide synthase , chemistry , nitric oxide , muscarinic acetylcholine receptor , enos , stimulation , agonist , biology , receptor
1 Using conventional and perforated patch‐clamp techniques, the inhibitory and stimulatory effects of acetylcholine (ACh) on β‐adrenergic regulation of the L‐type Ca 2+ current ( I Ca ) were studied in ventricular myocytes from wild‐type mice (WT) and from mice lacking endothelial nitric oxide synthase (eNOS or NOS3; NOS3‐KO mice). 2 To validate the direct comparison of ACh effects on β‐adrenergic responses, the sensitivity of I Ca to the β‐adrenergic agonist isoprenaline (Iso) was studied in both WT and NOS3‐KO mouse myocytes. I Ca sensitivity to Iso was not found to be significantly different in WT and NOS3‐KO myocytes: Iso increased I Ca with an EC 50 of 4.9 and 3.7 n m in WT and NOS3‐KO myocytes, respectively. 3 ACh‐induced inhibition of I Ca did not significantly differ in ventricular myocytes from WT and NOS3‐KO mice. ACh (10 μ m ) inhibited the stimulatory effect of 3 n m Iso by 39 and 35 % in WT and NOS3‐KO myocytes, respectively. 4 Exposure to and subsequent washout of ACh in the continuous presence of submaximally stimulating concentrations of Iso (1–3 n m ) resulted in a transient rebound stimulation of I Ca in both WT and NOS3‐KO mouse myocytes. The magnitude of the stimulatory effect of ACh did not significantly differ in WT and NOS3‐KO mice. 5 These results indicate that nitric oxide (NO) generated by NOS3 does not significantly affect the β‐adrenergic responsiveness of I Ca . The results also confirm previous work indicating that NO generated by NOS3 is not obligatory for muscarinic inhibition of the β‐adrenergically regulated I Ca in ventricular myocytes. Finally these results demonstrate for the first time that NO generated by NOS3 is not involved in muscarinic rebound stimulation of I Ca in ventricular myocytes.