Effect of P2 purinoceptor antagonists on kainate-induced currents in rat cultured neurons

The action of purinergic antagonists on kainate-induced currents was studie d in rat cortical neurons in primary culture using the whole-cell configura tion of the patch-clamp technique. The amplitude of the currents induced by kainate in cortical neurons was concentration-dependent (EC50 = 106 muM) P yridoxal-phosphate-6-azophenyll-2',4'-disulphonic acid 4-sodium (PPADS), a P2X antagonist, was ineffective in the reduction of the kainate-induced cur rent in cortical neurons, while 2,2'-pyridylisatogen (PIT), basilen blue (B B) and suramin, respectively two selective P2Y and a non-selective P7 recep tor antagonist, caused a reduction in the amplitude of the current induced by kainate. BB decreased the inward current induced by kainate at all holdi ng potentials and the reduction was dose-dependent (EC50 = 34 muM). The tot al conductance of the neurons for the kainate-induced current was significa ntly reduced (P<0.01) and the effect was completely reversible. BB furtherm ore reduced the kainate-induced current in granule and hippocampal neurons and decreased the amplitude of the <alpha>-amino-3-hydroxy-5-methyl-4-isoxa lepropionic acid (AMPA)-evoked current in cortical neurons. Cholera toxin ( ChTx) did not affect the action of BE on the kainate-induced currents in co rtical neurons and moreover, when guanosine 5'-o-(3-thiotriphosphate) (GTP gammaS) was added to the electrode solution, the kainate-induced currents w ere still reduced by 100 muM BB. The maximal response to kainate decreased in the presence of 20 muM BB without changing its EC50, indicating a non-co mpetitive mechanism of inhibition. These results demonstrate that preferent ial P2Y receptor antagonists are able to modulate the kainate and AMPA-indu ced currents in central neurons, suggesting a potential use of these compou nds as neuroprotective agents. (C) 2000 Elsevier Science B.V. All rights re served.