Negative inotropic effect of a CB2 agonist A-955840 in isolated rabbit ventricular myocytes is independent of CB1 and CB2 receptors
| Autor: | Ruth L. Martin, Lee C. Preusser, James T. Limberis, Michael Meyer, Michael J. Dart, Betty B. Yao, Jonathon Green, Xiaoqin Liu, Gary A. Gintant, Zhi Su, Bryan F. Cox, James S. Polakowski, Gilbert Diaz |
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| Rok vydání: | 2011 |
| Předmět: |
Inotrope
Male Sarcomeres medicine.medical_specialty Patch-Clamp Techniques Calcium Channels L-Type Heart Ventricles Toxicology Sarcomere Contractility Receptor Cannabinoid CB2 Inhibitory Concentration 50 Dogs Piperidines Receptor Cannabinoid CB1 In vivo Internal medicine Myocyte Medicine Animals Pharmacology (medical) Myocytes Cardiac Receptor Pharmacology business.industry Antagonist Myocardial Contraction Thiazoles Endocrinology Benzamides Ventricular pressure Pyrazoles Rabbits Rimonabant business |
| Zdroj: | Current drug safety. 6(5) |
| ISSN: | 2212-3911 |
| Popis: | A-955840, a selective CB2 agonist, has been shown to elicit concentration-dependent decreases in cardiac contractility in the anesthetized dog (decreased maximal velocity of left ventricular pressure development [LV dP/dt max]). However, it is unknown whether this represents a direct effect or a response dependent on other factors (such as autonomic tone and neurohumoral factors) present in vivo. This study examined if A-955840 had a direct effect on contractility of isolated cardiac myocytes, and if so to determine the potential mechanisms. Contractility was assessed in vitro using percent changes in maximal shortening velocity of sarcomeres (dL/dt max) and fractional shortening of sarcomere length (FS) in rabbit left ventricular myocytes. L-type calcium current in myocytes was recorded using wholecell voltage-clamp techniques. A-955840 reduced dL/dt max and FS in a reversible and concentration-dependent manner with an IC50 of 11.4 μg/mL (based on dL/dt max) which is similar to the estimated IC50 value of 9.8 μg/mL based on the effects of A-955840 on LV dP/dt max in anesthetized dogs. A-955840 (4.1 μg/mL) reduced myocyte contractility (%FS) to a similar extent in the absence and presence of a CB2 antagonist, SR-2 (24.0 ± 3.4 vs 23.1 ± 3.0 %, n=5) or a CB1 antagonist, Rimonabant (18.8 ± 2.3 vs 19.8 ± 2.7 %, n=5). A-955840 (4.1 μg/mL) also reduced L-type calcium current of rabbit ventricular myocytes (1.05 ± 0.11 vs 0.70 ± 0.12 nA, n=5, P < 0.01). These results suggest that A-955840 exerts direct negative inotropic effects on isolated rabbit ventricular myocytes, which is mediated by neither CB2 nor CB1 receptors, and consistent with off-target negative inotropy mediated by inhibition of the cardiac L-type calcium current. |
| Databáze: | OpenAIRE |
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