title: Adenosine receptors in brain membranes: binding of N6-cyclohexyl[3H]adenosine and 1,3-diethyl-8-[3H]phenylxanthine.
abstract: N6-Cyclohexyl[3H]adenosine ([3H]CHA) and 1,3-diethyl-8-[3H]phenylxanthine ([3H]DPX) to bind to adenosine receptors in brain membranes. The agonist [3H]CHA has high affinity in both bovine and guinea pig brain (Kd, 0.7 nM and 6 nM, respectively). [3H]CHA binding kinetics are slow (dissociation t1/2;60 min); binding is much higher at 25 degrees C than at 0 degrees C and is inhibited by guanine nucleotides. Potencies of nucleosides and xanthines in competing for [3H]CHA sites indicate that specific binding is entirely to A1 adenosine receptors. In bovine brain, the antagonist [3H]DPX exhibits high-affinity binding (Kd, 5 nM) to the same A1 receptors that bind [3H]CHA. Binding kinetics are rapid (dissociation t1/2, 1 min), and binding is moderately higher at 0 degrees C than at 25 degrees C. In guinea pig brain, [3H]DPX binding has only moderate affintiy (Kd 50 nM), and about 60% of specific binding is to sites that resemble A2 adenosine receptors.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000243:Adenosine Deaminase / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D006147:Guanine / Q000031:analogs & derivatives; D006168:Guinea Pigs; D008566:Membranes / Q000378:metabolism*; D009705:Nucleosides / Q000378:metabolism; D011687:Purines / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011983:Receptors, Purinergic; D013045:Species Specificity; D014970:Xanthines / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D009705:Nucleosides; D011687:Purines; D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D014970:Xanthines; C027512:1,3-diethyl-8-phenylxanthine; C027513:N(6)-cyclohexyladenosine; D006147:Guanine; D000243:Adenosine Deaminase; D000241:Adenosine