In Vitro Electrophysiologic Effects of Morphine in Rabbit Ventricular Myocytes

Guo-Sheng Xiao, Jing-Jun Zhou, Guan-Ying Wang, Chun-Mei Cao, Gui-Rong Li, Tak-Ming Wong
2005 Anesthesiology  
Morphine is widely used in patients undergoing surgical operations and is also reported to mediate cardioprotection of preconditioning. The current study determined effects of morphine at therapeutic to pharmacologic concentrations on cardiac action potential, L-type Ca 2؉ current (I Ca.L ), delayed rectifier K ؉ current (I K ), and inward rectifier K ؉ current (I K1 ) in isolated rabbit ventricular myocytes. Methods: Ventricular myocytes were enzymatically isolated from rabbit hearts. Action
more » ... tential and membrane currents were recorded in current and voltage clamp modes. Results: Morphine at concentrations from 0.01 to 1 M significantly prolonged cardiac action potential, and at 0.1 and 1 M slightly but significantly hyperpolarized the resting membrane potential. In addition, morphine at 0.1 M significantly augmented I Ca.L (at ؉10 mV) from 5.9 ؎ 1.9 to 7.3 ؎ 1.7 pA/pF (by 23%; P < 0.05 vs. control) and increased I K1 (at ؊60 mV) from 2.8 ؎ 1.0 to 3.5 ؎ 0.9 pA/pF (by 27%; P < 0.05 vs. control). Five M naltrindole (a selective ␦-opioid receptor antagonist) or 5 M norbinaltorphimine (a selective -opioid receptor antagonist) prevented the increase in I Ca.L induced by morphine, but 5 M CTOP (a selective -opioid receptor antagonist) did not. The three types of opioid antagonists did not affect the augmentation of I K1 by morphine. Morphine had no effect on I K . Conclusions: These results indicate that morphine prolongs action potential duration by increasing I Ca.L , an effect mediated by ␦and -opioid
doi:10.1097/00000542-200508000-00011 pmid:16052110 fatcat:pefsipggzbchdhjp6t2za2ppje