Effects of cardiac sympathetic nerve stimulation during adrenergic blockade on infarct size in anesthetized dogs.
beta-Adrenergic blockade has been shown to limit myocardial infarct size (IS) in anesthetized dogs. The objective of the present study was to determine whether sympathetic activation in the presence of beta-adrenergic blockade would alter IS. Chloralose-anesthetized dogs were divided into five groups. All hearts were neurally decentralized and paced at 150 beats/min. The circumflex coronary artery was ligated distal to the first major branch. Group 1 (n = 5) had no treatment. Group 2 (n = 6) received timolol (0.2 mg/kg) intravenously before and throughout occlusion. Group 3 (n = 7) underwent left stellate stimulation (LSS; 8 Hz, 5 ms, 7-10 V) immediately following coronary artery occlusion and for the duration of occlusion. Group 4 (n = 5) received timolol in addition to LSS. Group 5 animals (n = 6) received prazosin (0.5 mg/kg i.v.) and timolol before circumflex occlusion and LSS following coronary artery occlusion. After 6 h, Evans blue dye was injected into the left atrium while the circumflex artery distal to the ligation was simultaneously perfused with saline. Hearts were rapidly excised, and the left ventricle was sliced and photographed. IS was determined and expressed as a percentage of the area at risk by planimetry. The following mean +/- SEM values were measured: Group 1, 23.5 +/- 5.3; Group 2, 34.2 +/- 1.4; Group 3, 31.4 +/- 7.8; Group 4, 59.3 +/- 3.9; and Group 5, 25.6 +/- 5.3%. Significant differences were found between Group 4 and all other groups (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
K A
KA
Flatley
D V
DV
DeFily
J X
JX
Thomas
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000758:Anesthesia; D000818:Animals; D003331:Coronary Vessels / Q000503:physiopathology; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D006321:Heart / Q000294:innervation*; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology*; D013565:Sympatholytics / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D013565:Sympatholytics