Locally evoked potentials in slices of the rat nucleus accumbens: NMDA and non-NMDA receptor mediated components and modulation by GABA.
In a slice preparation of the rat nucleus accumbens (Acb), local electrical stimulation elicited a field potential composed of two negative peaks, followed by a positive wave. The early negative peak was identified as a non-synaptic compound action potential, the late negative peak as a monosynaptic population spike (PS) and the positive wave as a mixture of an excitatory and an inhibitory postsynaptic potential (PSP). Both the PS and the PSP exhibited a marked degree of paired-pulse facilitation. The quisqualate/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 2 microM) and the broadly acting glutamate receptor antagonist kynurenic acid (300 microM) reversibly abolished or reduced both the PS and PSP. In contrast, nicotinic, muscarinic and N-methyl-D-aspartate (NMDA) receptor antagonists had no suppressive action. Washout of Mg2+ from the superfusion medium reversibly enhanced and prolonged the PSP and this effect was blocked by the NMDA receptor antagonist D(-)-2-amino-5-phosphonopentanoic acid (D-AP-5). The gamma-aminobutyric acid antagonist picrotoxin (60 microM) enhanced the PS and induced secondary spikes which were superimposed on a prolonged PSP. Most of this prolongation was abolished by D-AP-5. It is concluded that locally evoked synaptic responses in the Acb are mediated by glutamate or aspartate, and that NMDA receptor mediated activity evoked by low frequency stimulation is substantial in Mg2(+)-free medium or during reduced GABAA receptor activity, but not under normal conditions.
Pennartz
C M
CM
Department of Experimental Zoology, University of Amsterdam, The Netherlands.
Boeijinga
P H
PH
Lopes da Silva
F H
FH
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001369:Axons / Q000502:physiology; D004151:Dipeptides / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000502:physiology; D009498:Neurotoxins / Q000494:pharmacology; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology*; D010424:Pentobarbital / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D011729:Pyridostigmine Bromide / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology*; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D014403:Tubocurarine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D015763:2-Amino-5-phosphonovalerate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D001285:Atropine; D004151:Dipeptides; D007736:Kynurenic Acid; D009498:Neurotoxins; D010424:Pentobarbital; D010852:Picrotoxin; D011729:Pyridostigmine Bromide; D011810:Quinoxalines; D011963:Receptors, GABA-A; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D013779:Tetrodotoxin; D014403:Tubocurarine; D005680:gamma-Aminobutyric Acid; C028929:gamma-glutamylglycine