title: On the specificity and type of receptor involved in carotid body chemoreceptor activation by adenosine in the cat.
abstract: Experiments were performed on cats anaesthetized with pentobarbitone in which carotid chemoreceptor activity was recorded from the peripheral end of a sectioned carotid sinus nerve. Intracarotid injections of adenosine 5'-triphosphate (ATP) (1-100 micrograms i.c.) caused a dose-related increase in chemosensory discharge which was delayed in onset. The adenosine uptake inhibitor dipyridamole potentiated the chemoexcitatory effects of injected adenosine and ATP. The stable ATP analogue alpha-beta-methylene ATP (10-100 micrograms i.c.) depressed chemoreceptor discharge, which suggests the presence of a P2-purinoceptor in the carotid body, and provides evidence that the chemoexcitatory effect of ATP results from its hydrolysis to adenosine 5'-phosphate (AMP)/adenosine. Adenine, inosine, guanosine, cytidine and uridine had no appreciable effect on chemoreceptor discharge. The adenosine R-site agonists 2'-chloroadenosine and N6-methyladenosine had chemoexcitatory effects which were similar to those of adenosine, whereas the P-site agonist 2'-deoxyadenosine had no appreciable effect on discharge. We conclude that the adenosine receptor in the cat carotid body has some of the characteristics of an R-site receptor according to the classification of Londos & Wolff (1977).
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002344:Carotid Body / Q000187:drug effects*; D002415:Cats; D004176:Dipyridamole / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000187:drug effects*; D011983:Receptors, Purinergic
chemical_list: D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D004176:Dipyridamole; D000255:Adenosine Triphosphate; D000241:Adenosine