Ionotropic P2X purinoreceptors mediate synaptic transmission in rat pyramidal neurones of layer II/III of somato-sensory cortex.
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-2H-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 microM) or alpha,beta-methylene ATP (10 microM) 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.
Pankratov
Y
Y
School of Biological Sciences, University of Manchester, 1.124 Stopford Building, Oxford Road, Manchester M13 9PT, UK.
Lalo
U
U
Krishtal
O
O
Verkhratsky
A
A
D015763:2-Amino-5-phosphonovalerate; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000502:physiology*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*
D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D018048:Receptors, Purinergic P2; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D015763:2-Amino-5-phosphonovalerate; D000255:Adenosine Triphosphate; D001640:Bicuculline