title: A subtype of adenosine receptors mediating pigment dispersion in leucophores of the medaka: evidence for an A2-receptor.
abstract: 1. Adenosine and its derivatives induced dispersion of leucosomes in leucophores of the medaka, Oryzias latipes. 2. Among the purines used, 5'-N-ethylcarboxiamideadenosine was the most effective and its potency was far greater than that of adenosine, N6-L-phenylisopropyladenosine and N6-cyclohexyladenosine. 3. Methylxanthines inhibited the purine action competitively, but beta adrenergic antagonists and dipyridamole did not. 4. Beta adrenergic agonists and forskolin synergistically augmented the purine action, while Li+ blocked it competitively. 5. The results suggest that medaka leucophores possess A2 adenosine receptors on the cell membranes, the stimulation of which induces leucosome-dispersion response by increasing the cellular level of cyclic AMP through activation of adenylate cyclase activity.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D002856:Chromatophores / Q000187:drug effects / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D003532:Cyprinodontiformes / Q000502:physiology*; D004176:Dipyridamole / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D009990:Oryzias / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology*; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*; D014970:Xanthines / Q000494:pharmacology*
chemical_list: D002395:Catecholamines; D002712:Chlorides; D011687:Purines; D011983:Receptors, Purinergic; D014970:Xanthines; D005576:Colforsin; D004176:Dipyridamole; D008094:Lithium; D011433:Propranolol; D018021:Lithium Chloride; D000241:Adenosine