title: Adenosine receptor agonists inhibit K+-evoked Ca2+ uptake by rat brain cortical synaptosomes.
abstract: The uptake of Ca2+ by a K+-depolarized rat brain cerebral cortical crude synaptosomal preparation (P2 fraction) was investigated. The characteristics of the Ca2+ uptake system are similar to those observed by other investigators. The preparation is also a suitable model with which to study the effects of adenosine on Ca2+ uptake and neurotransmitter release, as it is generally accepted that K+-evoked Ca2+ uptake is intimately related to depolarization-induced release of neurotransmitters. We have demonstrated that an extracellular receptor is involved in mediating the adenosine-evoked inhibition of K+-evoked Ca2+ uptake. The pharmacological properties of the receptor suggest that it may be similar in some respects to the A2-receptor associated with adenylate cyclase. The adenosine uptake inhibitor, dipyridamole, potentiated the action of adenosine, suggesting that re-uptake is important in controlling the extracellular adenosine concentration and thus in the regulation of the adenosine receptor. The adenosine receptor antagonist theophylline inhibited the effects of adenosine. Calmodulin inhibited K+-evoked uptake of Ca2+ by the synaptosomal fraction.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011983:Receptors, Purinergic; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
chemical_list: D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D000241:Adenosine; D011188:Potassium; D002118:Calcium