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

Abstract

The action of purinergic antagonists on kainate-induced currents was studied in rat cortical neurons in primary culture using the whole-cell configuration of the patch-clamp technique. The amplitude of the currents induced by kainate in cortical neurons was concentration-dependent (EC 50=106 μM). Pyridoxal-phosphate-6-azophenyll-2′,4′-disulphonic acid 4-sodium (PPADS), a P2X antagonist, was ineffective in the reduction of the kainate-induced current in cortical neurons, while 2,2′-pyridylisatogen (PIT), basilen blue (BB) and suramin, respectively two selective P2Y and a non-selective P2 receptor antagonist, caused a reduction in the amplitude of the current induced by kainate. BB decreased the inward current induced by kainate at all holding potentials and the reduction was dose-dependent (EC 50=34 μM). The total conductance of the neurons for the kainate-induced current was significantly reduced ( P<0.01) and the effect was completely reversible. BB furthermore reduced the kainate-induced current in granule and hippocampal neurons and decreased the amplitude of the α-amino-3-hydroxy-5-methyl-4-isoxalepropionic acid (AMPA)-evoked current in cortical neurons. Cholera toxin (ChTx) did not affect the action of BB on the kainate-induced currents in cortical neurons and moreover, when guanosine 5′- o-(3-thiotriphosphate) (GTPγS) was added to the electrode solution, the kainate-induced currents were still reduced by 100 μM BB. The maximal response to kainate decreased in the presence of 20 μM BB without changing its EC 50, indicating a non-competitive mechanism of inhibition. These results demonstrate that preferential P2Y receptor antagonists are able to modulate the kainate and AMPA-induced currents in central neurons, suggesting a potential use of these compounds as neuroprotective agents.