title: Effect of adenosine on 45Ca2+ uptake by electrically stimulated rat brain synaptosomes.
abstract: The effect of adenosine on 45Ca2+ uptake by rat brain synaptosomes stimulated by electrical pulses was investigated. 45Ca2+ uptake was voltage dependent. Adenosine (1 nM-1 microM) decreased the uptake of 45Ca2+ induced by electrical stimulation (amplitude, 20 V; duration, 400 microseconds; frequency, 10 pulses/s) in a concentration-dependent manner. At a concentration of 1 microM, adenosine almost abolished the 45Ca2+ uptake induced by electrical stimulation (92.9 +/- 5.3% inhibition), but when the calcium uptake was induced by high-K+ (60 mM) medium, the effect of adenosine (1 microM) was smaller (43.8 +/- 5.2% inhibition). The inhibitory effect of 1 microM adenosine on calcium uptake induced by electrical stimulation was antagonized by 1,3-dipropyl-8-p-sulfophenylxanthine (5 microM). The possibility that adenosine interacts with the calcium channels opened by electrical stimulation is discussed.
authors.affiliation: Laboratory of Pharmacology, Gulbenkian Institute of Science, Oeiras, Portugal.
authors.forename: M L
authors.initials: ML
authors.lastname: Gonçalves
authors.forename: F
authors.initials: F
authors.lastname: Pinto
authors.forename: J A
authors.initials: JA
authors.lastname: Ribeiro
mesh_terms: D000241:Adenosine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000493:pharmacokinetics*; D002132:Calcium Radioisotopes; D003470:Culture Media; D004558:Electric Stimulation; D008297:Male; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000378:metabolism*; D013997:Time Factors; D014970:Xanthines / Q000494:pharmacology
chemical_list: D002132:Calcium Radioisotopes; D003470:Culture Media; D014970:Xanthines; C053896:1,3-dipropyl-8-(4-sulfophenyl)xanthine; D000241:Adenosine; D011188:Potassium; D002118:Calcium