Ionotropic P2X purinoreceptors mediate synaptic transmission in rat pyramidal neurones of layer II/III of somato-sensory cortex |
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Authors: | Y Pankratov† U Lalo† O Krishtal† A Verkhratsky |
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Institution: | School of Biological Sciences, University of Manchester, 1.124 Stopford Building, Oxford Road, Manchester M13 9PT, UK;Bogomoletz Institute of Physiology, Bogomoletz Str. 4, Kiev-24, Ukraine |
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Abstract: | Fast P2X receptor-mediated excitatory postsynaptic current (EPSC) was identified in pyramidal neurones of layer II/III of somato-sensory cortex in acutely isolated slices obtained from the brain of 17- to 22-day-old rats. The EPSCs were elicited by electrical stimulation of vertical axons originating from layer IV-VI neurones at 0.1 Hz in the presence of bicuculline. When the glutamatergic EPSC was blocked by saturating concentrations of glutamate receptor inhibitors 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo-f]-quinoxaline-7-sulphonamide (NBQX) and D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5), a small EPSC component was recorded from 90 % of neurones tested. This residual EPSC was not affected by selective blockers of nicotinic (hexamethonium) or serotonin ( N -(1-azabicyclo-2.2.2]oct-3-yl)-6-chloro-4-methyl-3-oxo-3,4-dihydro-2 H -1,4-benzoxazine-8-carboxamide hydrochloride, Y-25130) receptors, but it was reversibly inhibited by the antagonists of P2X receptors NF023 (8,8'-carbonylbis(imino-3,1-phenylenecarbonylimino)]bis-1,3,5-naphthalene-trisulphonic acid), NF279 (8,8'-carbonylbis (imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino)]bis-1,3,5-naphthalene-trisulphonic acid) and PPADS (pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid). Application of ATP (10 μ m ) or α,β-methylene ATP (10 μ m ) to pyramidal neurones, acutely isolated from cortical slices, evoked inward currents (30 to 200 pA) in 65 % of cells tested. The relative calcium/caesium permeability ( P Ca/ P Cs) of P2X receptors was 12.3 as estimated from the reversal potential of ATP-induced current measured at different extracellular calcium concentrations. We concluded that P2X purinoreceptors are activated during synaptic transmission in neocortex. |
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