title: Adenosine A1 receptor-mediated inhibition of cyclic AMP accumulation in type-2 but not type-1 rat astrocytes.
abstract: The effects of adenosine receptor-selective ligands on [3H]cyclic AMP accumulation have been investigated in type-1 and type-2 astrocyte-enriched cultures derived from neonatal rat forebrains. In type-1 astrocytes, 5'-N-ethylcarboxamidoadenosine (NECA) caused a concentration-dependent increase in [3H]cyclic AMP accumulation (EC50 = 1.2 microM) which was antagonised by pretreatment with either xanthine amine congener (8-[4-[[[[(2-aminoethyl)amino]carbonyl]methyl]oxy]-phenyl]- 1,3-dipropylxanthine, apparent Kd = 9 nM) or PD115,199 (N-[2-(dimethylamino)ethyl]-N-methyl-4-(1,3-dipropylxanthine) benzene sulphonamide, apparent Kd = 122 nM). In these cultures, N6-cyclopentyladenosine (CPA), did not affect forskolin- or isoprenaline-mediated elevations of [3H]cyclic AMP accumulation. These data indicate that type-1 astrocytes possess adenosine A2B but not adenosine A1 receptors coupled to adenylyl cyclase. In type-2 astrocyte-enriched cultures, 10 microM NECA caused significant elevations of [3H]cyclic AMP accumulation which were similarly inhibited by either 1 microM xanthine amine congener or 10 microM PD115,199 suggesting that they were primarily due to adenosine A2B receptor stimulation. However, CGS 21680 ((2-[[4-(2-carboxyethyl) phenethyl]-amino]adenosine-5'-N-ethylcarboxamide, 10 microM), also significantly increased [3H]cyclic AMP accumulation in type-2 astrocytes suggesting the additional presence of adenosine A2A receptors. Forskolin-mediated elevations of [3H]cyclic AMP accumulation in type-2 astrocytes were inhibited in a concentration-dependent manner by CPA. This effect was reversed by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 0.1 microM), confirming the presence of adenosine A1 receptors negatively coupled to adenylyl cyclase in type-2 astrocytes.
authors.affiliation: Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham, UK.
authors.forename: M C
authors.initials: MC
authors.lastname: Peakman
authors.forename: S J
authors.initials: SJ
authors.lastname: Hill
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide); D000704:Analysis of Variance; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000819:agonists / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D007150:Immunohistochemistry; D058906:Purinergic P1 Receptor Agonists; D051381:Rats; D018047:Receptors, Purinergic P1 / Q000502:physiology*
chemical_list: D058906:Purinergic P1 Receptor Agonists; D018047:Receptors, Purinergic P1; D019830:Adenosine-5'-(N-ethylcarboxamide); D000242:Cyclic AMP; D000241:Adenosine