Poor vasoconstrictor response to adrenergic stimulation in the arteriovenous anastomoses present in the carotid vascular bed of young Yorkshire pigs.
Studies using electromagnetic flowmeters and radioactive labeled microspheres (15 +/- 1 micron) have revealed that about 80% of the total common carotid artery blood flow in young domestic pigs (12-14 weeks) is shunted through arteriovenous anastomoses (AVAs). To investigate the influence of the sympathetic nervous system we measured the distribution of carotid blood flow before and after cervical sympathetic nerve stimulation (2-16 Hz), intracarotid infusions of noradrenaline (0.025-0.2 micrograms X kg-1 X min-1) or intracarotid bolus injections of noradrenaline (0.3 and 1.0 micrograms X kg-1) and clonidine (1 and 5 micrograms X kg-1). The first two interventions did not exert any effect, but bolus injections of noradrenaline and clonidine, achieving high local concentrations temporarily, caused a short-lasting decrease in AVA-flow, which was attenuated by phentolamine (1 mg X kg-1). It is concluded that the sympathetic nervous system in the carotid vascular bed of young Yorkshire pigs is poorly developed.
D000818:Animals; D001163:Arteriovenous Anastomosis / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D002339:Carotid Arteries / Q000187:drug effects*; D003000:Clonidine / Q000494:pharmacology; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D010646:Phentolamine / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects*
D003000:Clonidine; D009638:Norepinephrine; D010646:Phentolamine