The syntheses and A1 and A2a adenosine binding activities of some new 1-aryl-1,4-dihydro-3-methyl[1]benzopyrano[2,3-c]pyrazol-4-ones, 1-aryl-4,9-dihydro-3-methyl-1H-pyrazolo[3,4-b]-quinolin-4-ones, and 1-aryl-1H-imidazo[4,5-b]quinoxalines are reported. Some compounds show A1 adenosine receptor affinity and selectivity. Structure-activity relationships on these new classes of adenosine receptor ligands are defined.
Synthesis of Some Tricyclic Heteroaromatic Systems and Their A1 and A2a Adenosine Binding Activity. -The title compounds (Ic), (Id), and (Ie) are potent and selective A1 adenosine receptor ligands. Imidazoquinoxaline analogues are less active. -(COLOTTA, V.; CECCHI, L.; CATARZI, D.; FILACCHIONI, G.; MARTINI, C.; TACCHI, P.; LUCACCHINI, A.; Eur.
In striaturn and several other tissues, a guanine nucleotide binding protein (G,) couples A, adenosine receptor to activation of adenylyl cyclase. We have examined the effect of guanine nucleoside diphosphate and triphosphate on 13H]CGS 21680 binding to A, , adenosine receptors of rat striaturn. Both GDP and GTP inhibited specific 13H]CGS 21680 binding to rat striatal membranes by 50% at about 0.1 mM. GMP was inhibitory only at higher concentrations, and the estimated I C, , value was greater than 1 mM. The nonhydrolyzable analog of GTP, Gpp(NH)p, was as potent as GTP with an I C, , value of approximately 86 FM. These results suggest that the regulation of adenosine receptor binding properties by guanine nucleotides i s independent of G, activation, since inhibition of agonist binding is achieved by addition of both guanine nucleoside diphosphate and triphosphate. o 1993 Wiley-Liss, Inc.
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