title: Biochemical and pharmacological evidence for the presence of A1 but not A2a adenosine receptors in the brain of the low vertebrate teleost Carassius auratus (goldfish).
abstract: In whole brain membranes of goldfish, 3H-chlorocyclopentyladenosine bound to adenosine A1 receptors. The A1 receptors were ubiquitously distributed in the brain with a maximum in the hypothalamus and a minimum in the spinal cord. In superfused goldfish cerebellar slices, cyclohexyladenosine inhibited the cyclic AMP accumulation stimulated by forskolin and the selective adenosine A1 receptor antagonist, 8-cyclopentyltheophylline, reversed this effect. In the same brain preparation, 30 mM K+ stimulated the release of glutamate, glutamine, glycine and GABA in a Ca(2+)-dependent manner, whereas the aspartate and taurine release was Ca(2+)-independent. Cyclohexyladenosine, in a dose-dependent manner, inhibited the 30 mM K(+)-evoked release of glutamate whereas that of aspartate was unaffected. The CHA inhibition of glutamate-evoked release was reversed by 8-cyclopentyltheophylline. The adenosine A2a receptors were not detectable in whole brain membranes of goldfish either using the specific agonist 3H-CGS 21680 or 3H-5'-N-ethylcarboxamidoadenosine. The presence of A2b seems to be suggested by the NECA stimulation of cyclic AMP accumulation, which was reversed by 8-cyclopentyltheophylline. The results, taken together, indicate that adenosine has a neuromodulatory function in the nervous system of lower vertebrates which is comparable to that described in mammalian brain.
authors.affiliation: Institute of Pharmacology and Pharmacognosy, Faculty of Pharmacy, University of Trieste, Italy.
authors.forename: A M
authors.initials: AM
authors.lastname: Rosati
authors.forename: U
authors.initials: U
authors.lastname: Traversa
authors.forename: R
authors.initials: R
authors.lastname: Lucchi
authors.forename: A
authors.initials: A
authors.lastname: Poli
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D006054:Goldfish / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008322:Mammals / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000502:physiology*; D010627:Phenethylamines / Q000378:metabolism; D011869:Radioligand Assay; D018047:Receptors, Purinergic P1 / Q000032:analysis* / Q000502:physiology; D013045:Species Specificity; D013696:Temperature
chemical_list: D018377:Neurotransmitter Agents; D010627:Phenethylamines; D018047:Receptors, Purinergic P1; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); C027513:N(6)-cyclohexyladenosine; C058394:2-chloro-N(6)cyclopentyladenosine; D000241:Adenosine