Adenosine A(1) receptors inhibit Ca2+ channels coupled to the release of ACh, but not of GABA, in cultured retina cells

We investigated the effect of adenosine A(1) receptors on the release of ac etylcholine (ACh) and GABA, and on the intracellular calcium concentration ([Ca2+](i)) response in cultured chick amacrine-like neurons, stimulated by KCl depolarization. The KCl-induced release of [H-3]ACh, but not the relea se of [C-14]GABA, was potentiated when adenosine A(1) receptor activation w as prevented by perfusing the cells with adenosine deaminase (ADA) or with 1,3-dipropyl-8-cycloentylxanthine (DPCPX). The changes in the [Ca2+](i) ind uced by KCI depolarization, measured in neurite segments of single cultured cells, were also modulated by endogenous adenosine, acting on adenosine A( 1) receptors. Our results show that adenosine A(1) receptors inhibit Ca2+ e ntry coupled to ACh release, but not to the release of GABA, suggesting tha t the synaptic vesicles containing each neurotransmitter are located in dif ferent zones of the neurites, containing different VSCC and/or different de nsities of adenosine A(1) receptors. (C) 2000 Elsevier Science B.V. All rig hts reserved.