Left stellate stimulation: regional myocardial flows and ischemic injury in dogs.
The effects of left stellate ganglion stimulation (LSGS) on regional myocardial blood flow (RMBF) and epicardial S-T segment were investigated in the normal and ischemic myocardium of anesthetized dogs. In nonischemic myocardium LSGS decreased calculated coronary resistance, increased RMBF, and reduced the endocardial-to-epicardial (endo-to-epi) ratio. These effects were reversed after atenolol (1 mg/kg) and abolished after combined atenolol and phenoxybenzamine (3 mg/kg) treatments. In ischemic myocardium LSGS did not change RMBF but increased S-T segment. However, after atenolol, LSGS increased ischemic RMBF and the ischemic-to-nonischemic areas flow ratio (reverse coronary steal phenomenon), these effects being abolished by phenoxybenzamine. We conclude that 1) LSGS increases RMBF and decreases endo-to-epi ratio in nonischemic areas by beta 1-adrenergic stimulation through metabolic autoregulation, 2)beta 1-adrenergic blockade in nonischemic areas unmasks alpha-adrenergic vasoconstriction inducing a redistribution of flow towards ischemic areas, and 3) further elevation of S-T segment by LSGS is due to oxygen requirements enhancement by beta 1-adrenoceptors stimulation.
D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D003326:Coronary Circulation; D003327:Coronary Disease / Q000503:physiopathology*; D004285:Dogs; D004558:Electric Stimulation; D004562:Electrocardiography; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D005728:Ganglia, Sympathetic / Q000502:physiology*; D008297:Male; D010643:Phenoxybenzamine / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D012039:Regional Blood Flow
D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010643:Phenoxybenzamine; D001262:Atenolol; D004837:Epinephrine