Pharmacological evidence that NMDA receptors contribute to mono- and di-synaptic potentials in slices of mouse olfactory cortex.
Experiments have been carried out using slices of olfactory cortex of the mouse perfused in solution containing Mg2+ (1 mM) and in which the lateral olfactory tract was stimulated at a frequency of 1 pulse/5 sec to avoid polysynaptic activity. Application of the N-methyl-D-aspartate antagonist D-(-)-2-amino-5-phosphonopentanoic acid (APP, 25 microM) suppressed a low amplitude component of the potential, the latency to onset of which corresponded with that of the monosynaptically evoked N-wave in 14 of the 17 slices tested and duration of which exceeded that of the N-wave. A residual potential, recorded in slices to which the quisqualate-/kainate-selective antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) had been applied at a concentration of 10microM, was identical to the potential suppressed by APP. The residual potential in the presence of DNQX was blocked by APP, 7-chlorokynurenate (25 microM) and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK801, 0.125-2 microM). It was potentiated in area by exogenous D-serine (1 mM) and in slices preincubated and perfused with Mg(2+)-free solution. It is concluded that, in addition to receptors of the quisqualate/kainate categories, N-methyl-D-aspartate receptors also contribute to both mono- and di-synaptic excitations in the olfactory cortex.
University Department of Medicine and Pharmacology, Royal Hallamshire Hospital, Sheffield, U.K.
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Collins
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects*; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D051379:Mice; D016202:N-Methylaspartate / Q000494:pharmacology; D009830:Olfactory Bulb / Q000187:drug effects*; D011810:Quinoxalines / Q000494:pharmacology; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000187:drug effects*; D013237:Stereoisomerism; D013569:Synapses / Q000187:drug effects*
D011810:Quinoxalines; D016194:Receptors, N-Methyl-D-Aspartate; C056723:FG 9041; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D007736:Kynurenic Acid; D008274:Magnesium; C057013:7-chlorokynurenic acid