title: P1-purinoceptors in the cerebrovascular bed of the goat in vivo.
abstract: The possible existence and function of specific P1-purinoceptors in the cerebrovascular bed of the unanesthetized goat have been investigated. Blood flow to one cerebral hemisphere (cerebral blood flow) was measured by means of an electromagnetic flow probe previously implanted around the ipsilateral internal maxillary artery. The injection of adenosine, AMP, ADP and ATP (3-30 micrograms) directly into the internal maxillary artery increased cerebral blood flow and decreased cerebrovascular resistance in a dose-dependent manner. Continuous infusion of 8-phenyltheophylline (8-PT), 100 micrograms/min, into the internal maxillary artery did not alter the resting cerebral blood flow or the cerebrovascular resistance, but significantly inhibited the cerebral vasodilation induced by adenosine, AMP, ADP and, to a lesser degree, ATP. The acetylcholine- and histamine-induced cerebral vasodilation was unaffected by 8-PT. These results indicate that adenosine, AMP, ADP and, at least in part, ATP increase cerebral blood flow by acting on specific P1-purinoceptors located in the cerebrovascular wall. These P1-purinoceptors do not appear to be tonically activated under physiological conditions.
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000187:drug effects; D005260:Female; D006041:Goats; D006339:Heart Rate / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D011983:Receptors, Purinergic / Q000378:metabolism*; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
chemical_list: D011983:Receptors, Purinergic; D002245:Carbon Dioxide; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine