Abstract
The recovery process of sympathetic neuronal function (SN) and β-adrenoceptors (AR) after reperfusion following transient ischemia is not fully understood. We investigated (1) serial changes in SN and AR after transient ischemia and (2) effect of brief ischemia before sustained ischemia on SN in rat hearts. Methods: (1) Left coronary artery of Wistar rats was ligated for 15-min followed by reperfusion. SN and AR were assessed by dual-tracer method of 131I-metaiodobenzylguanidine (MIBG) and 125I-cyanopindolol (ICYP). (2) Five-min coronary occlusion before the 30-min occlusion was performed in Wistar rats and cardiac MIBG uptake was determined 3 days after ischemia. Cardiac interstitial norepinephrine (iNE) during 30-min coronary occlusion was measured using microdialysis method. Results: (1) Decrease of MIBG uptake in ischemic region was modest at day 1 after reperfusion and was most severe at days 7 and 14. It was partially restored at day 28. In contrast, the ICYP uptake was severely decreased until day 3 and recovered thereafter. (2) MIBG uptake in ischemic region was greater in rats with 5-min ischemia before 30-min ischemia than in rats without it, associated with lower levels of iNE in rats with brief ischemia. Conclusion: Impairment of cardiac SN after transient ischemia is sustained for a long period and its recovery course is quite different from that of AR. A brief episode of ischemia before prolonged ischemia inhibits deterioration of SN after ischemia, phenomenon of neural preconditioning. [Jpn J Physiol 54 Suppl:S61 (2004)]
