Influence of Ca2+ channel modulators on [3H]purine release from rat cultured glial cells.
[3H]Purine release from rat striatum astrocyte cultures was studied at 14 days in vitro (DIV). Superfusion of cultures with a Ca(2+)-free medium + 0.5 mM ethylene glycol-bis(beta-aminoethylether)N,N,N',N'-tetracetic acid (EGTA) reduced the electrically evoked [3H]purine release. Nimodipine only at the concentration of 10 microM modified [3H]purine outflow whereas 0.1 microM omega-conotoxin and 0.03-0.1 microM nitrendipine reduced the evoked one. Superfusion of cultures with 0.1 microM omega-conotoxin + 0.1 microM nitrendipine antagonized the evoked [3H]purine release similarly to each drug given alone. Neither nitrendipine nor omega-conotoxin influenced the uptake of 45Ca2+ by the cultures. The treatment of cells with the Ca2+ agonist Bay K 8644 did not affect [3H]purine release or the 45Ca2+ uptake. The drug did not either alter [Ca2+]i, evaluated by loading the cells with 3 microM Fura-2/AM. 10-30 microM 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester (TMB-8), a blocker of intracellular Ca2+ discharge, significantly reduced the evoked [3H]purine release. On the other hand, 2 microM thapsigargin, an inhibitor of the ion store Ca2+ ATPase, was able to increase either the culture [3H]purine release or the [Ca2+]i. Together, the findings indicate that voltage-sensitive calcium channels (VSCCs) of the neuronal N and L-types are not involved in the modulation of [3H]purine release from rat cultured astrocytes whereas Ca2+ coming from intracytoplasmic stores seems to play a prevailing role. Moreover, agents which block VSCC, seem to be able to affect [3H]purine outflow with mechanisms other than VSCC gating.
Ballerini
P
P
Institute of Pharmacology and Bio-Medical Technologies, School of Medicine, University of Chieti, Italy.
Ciccarelli
R
R
Di Iorio
P
P
Giuliani
P
P
Caciagli
F
F
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D004558:Electric Stimulation; D005333:Fetus; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D007700:Kinetics; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009568:Nitrendipine / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D011687:Purines / Q000378:metabolism*; D011865:Radioisotope Dilution Technique; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014316:Tritium; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D005456:Fluorescent Dyes; D010455:Peptides; D011687:Purines; D020960:omega-Conotoxins; D014316:Tritium; C049925:fura-2-am; C053423:Conus magus toxin; D004533:Egtazic Acid; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009568:Nitrendipine; D016257:Fura-2; C030985:purine