title: Co-localized adenosine A1 and gamma-aminobutyric acid B (GABAB) receptors of cerebellum may share a common adenylate cyclase catalytic unit.
abstract: In synaptosomal membranes from rat cerebellum, additive responses to adenylate cyclase activity are observed between the beta adrenergic receptors present on the Purkinje cells and the adenosine A-1 receptors or gamma-aminobutyric acid B (GABAB) receptors, which are both associated with the granule cells. In contrast, nonadditive responses are found with the activation of the adenosine A-1 and the GABAB receptors. Because both receptors are mainly associated with the same cell type, the nonadditive response indicates an interaction between the adenosine A-1, GABAB receptors and the adenylate cyclase. The present study suggests that the nonadditivity results from a limited number of adenylate cyclase catalytic units, which both receptor systems share. This conclusion was derived indirectly by showing that 1) a GABAB agonist did not affect the adenosine A-1 recognition site; 2) both receptors additively activated the high-affinity guanosine 5'-triphosphatase, which is believed to reflect the activation of the inhibitory guanine nucleotide unit; and 3) the nonadditivity was still observed after stimulation of adenylate cyclase activity with forskolin.
authors.forename: W J
authors.initials: WJ
authors.lastname: Wojcik
authors.forename: D
authors.initials: D
authors.lastname: Cavalla
authors.forename: N H
authors.initials: NH
authors.lastname: Neff
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002531:Cerebellum / Q000032:analysis*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010660:Phenylisopropyladenosine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000032:analysis*; D011963:Receptors, GABA-A / Q000032:analysis*; D011983:Receptors, Purinergic; D013570:Synaptic Membranes / Q000032:analysis / Q000187:drug effects
chemical_list: D046911:Macromolecular Substances; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D011983:Receptors, Purinergic; D010660:Phenylisopropyladenosine; C027513:N(6)-cyclohexyladenosine; D020558:GTP Phosphohydrolases; D000262:Adenylyl Cyclases; D001418:Baclofen; D000241:Adenosine; D007545:Isoproterenol; D009638:Norepinephrine