title: Alpha adrenoceptor regulation of coronary artery blood flow in normal and stenotic canine coronary arteries.
abstract: The response of systemic blood pressure, heart rate, lead II ECG and left circumflex (LCX) coronary artery blood flow to left cardiac sympathetic nerve stimulation was measured in pentobarbital-anesthetized, open chest, spinal transected and vagotomized dogs. After beta adrenoceptor blockade, left cardiac sympathetic nerve stimulation produced frequency dependent decreases in LCX blood flow. Selective alpha-2 adrenoceptor blockade with idazoxan produced a greater inhibition of this decrease in LCX blood flow than did selective alpha-1 adrenoceptor blockade with prazosin. In an additional population of dogs which were similarly prepared but were not spinally transectioned or pretreated with a beta adrenoceptor antagonist, left cardiac sympathetic nerve stimulation produced an increase in LCX blood flow in all animals which reached a maximum within 40 sec, and then began to decline slowly. However, after beta adrenoceptor blockade, identical stimulation parameters produced only a decline in LCX blood flow which returned to the level of control resting blood flow by the end of the stimulation period. Both selective alpha-2 adrenoceptor blockade with idazoxan and selective alpha-1 adrenoceptor blockade with prazosin produced an inhibition of the LCX blood flow decrease provoked by left cardiac sympathetic nerve stimulation in dogs pretreated with beta adrenoceptor antagonists. Idazoxan produced a slightly greater inhibition of the LCX blood flow decrease than did prazosin, suggesting a greater role for postjunctional vascular alpha-2 adrenoceptors in LCX blood flow regulation during cardiac sympathetic nerve stimulation. The presence of a severe coronary artery stenosis reduced, but did not inhibit, the increase in LCX blood flow in response to cardiac sympathetic nerve stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001157:Arterial Occlusive Diseases / Q000503:physiopathology*; D001794:Blood Pressure; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels; D004146:Dioxanes / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000502:physiology; D006339:Heart Rate; D019329:Idazoxan; D008297:Male; D009248:Nadolol / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000502:physiology
chemical_list: D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D011942:Receptors, Adrenergic, alpha; D009248:Nadolol; D011224:Prazosin; D019329:Idazoxan