Functional adenosine A1 receptors in goldfish brain: regional distribution and inhibition of K(+)-evoked glutamate release from cerebellar slices.
In goldfish brain, [3H]cyclohexyladenosine binding sites are ubiquitously distributed with a maximum in the hypothalamus and a minimum in the spinal cord. The binding parameters measured in cerebellar membranes (Kd = 0.88 +/- 0.08 nM; Bmax = 59.65 +/- 2.62 fmol/mg protein) are not significantly different from those of the whole brain. In perfused goldfish cerebellar slices, stimulation of cyclic AMP accumulation by 10(-5) M forskolin was markedly reduced (58.7%) by treatment with 10(-4) M cyclohexyladenosine, an adenosine A1 receptor agonist, and the reduction was reversed in the presence of 10(-4) M 8-cyclopentyltheophylline, a selective A1 receptor antagonist. 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 inhibited the 30 mM K(+)-evoked release of glutamate in a dose-related manner. This effect was reversed by 8-cyclopentyltheophylline. These results support the hypothesis that adenosine A1 receptors present in goldfish cerebellum are involved in the modulation of glutamate transmitter release.
Lucchi
R
R
Department of Biology, Faculty of Sciences, University of Bologna, Italy.
Poli
A
A
Traversa
U
U
Barnabei
O
O
D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology; D002531:Cerebellum / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D005576:Colforsin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D006054:Goldfish / Q000502:physiology*; D066298:In Vitro Techniques; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D018047:Receptors, Purinergic P1 / Q000187:drug effects / Q000502:physiology*; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology
D000596:Amino Acids; D005971:Glutamates; D018047:Receptors, Purinergic P1; D005576:Colforsin; C053907:8-cyclopentyl-1,3-dimethylxanthine; C027513:N(6)-cyclohexyladenosine; D018698:Glutamic Acid; D013806:Theophylline; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D000241:Adenosine; D011188:Potassium; D002118:Calcium