Either desipramine or TMB-8 suppresses cyanide-induced norepinephrine efflux from in vivo cardiac sympathetic nerves of cats |
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Authors: | Yahagi N Yamazaki T Akiyama T |
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Institution: | Department of Cardiac Physiology, Research Institute, National Cardiovascular Center, Suita, Osaka, Japan. |
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Abstract: | To investigate the effect of hypoxia on endogenous norepinephrine (NE) release from cardiac sympathetic nerve ending, we administered sodium cyanide (NaCN) for 30 min into the myocardial interstitial space through a dialysis probe and measured dialysate NE levels. During the NaCN perfusion, a marked and concentration-dependent increase in dialysate NE was observed. This cyanide-induced NE response was suppressed by pretreatment with despiramine (a membraneous NE transport inhibitor). Furthermore, the cyanide-induced NE response was suppressed by pretreatment with TMB-8 (intracellular Ca(2+) antagonist) but unaffected by omega-conotoxin GVIA (NE releasing inhibitor). Our data suggest that two (desipramine or TMB-8 suppressive) mechanisms contributed to the amount of NE efflux induced by cyanide in in vivo cardiac sympathetic nerve. |
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Keywords: | Ca2+ overload Carrier-mediated transport Hypoxia Ischemia Microdialysis Na+ overload |
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