Locally evoked potentials in slices of the rat nucleus accumbens: NMDA and non-NMDA receptor mediated components and modulation by GABA

Brain Res. 1990 Oct 8;529(1-2):30-41. doi: 10.1016/0006-8993(90)90808-o.


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.

MeSH terms

  • 2-Amino-5-phosphonovalerate / pharmacology
  • 6-Cyano-7-nitroquinoxaline-2,3-dione
  • Animals
  • Atropine / pharmacology
  • Axons / physiology
  • Dipeptides / pharmacology
  • Electric Stimulation
  • Evoked Potentials / drug effects
  • In Vitro Techniques
  • Kynurenic Acid / pharmacology
  • Male
  • Neurons / physiology
  • Neurotoxins / pharmacology
  • Nucleus Accumbens / drug effects
  • Nucleus Accumbens / physiology*
  • Pentobarbital / pharmacology
  • Picrotoxin / pharmacology
  • Pyridostigmine Bromide / pharmacology
  • Quinoxalines / pharmacology
  • Rats
  • Rats, Inbred Strains
  • Receptors, GABA-A / drug effects
  • Receptors, GABA-A / physiology
  • Receptors, N-Methyl-D-Aspartate / drug effects
  • Receptors, N-Methyl-D-Aspartate / physiology*
  • Receptors, Neurotransmitter / drug effects
  • Receptors, Neurotransmitter / physiology*
  • Tetrodotoxin / pharmacology
  • Time Factors
  • Tubocurarine / pharmacology
  • gamma-Aminobutyric Acid / physiology*


  • Dipeptides
  • Neurotoxins
  • Quinoxalines
  • Receptors, GABA-A
  • Receptors, N-Methyl-D-Aspartate
  • Receptors, Neurotransmitter
  • Picrotoxin
  • gamma-glutamylglycine
  • Tetrodotoxin
  • gamma-Aminobutyric Acid
  • 6-Cyano-7-nitroquinoxaline-2,3-dione
  • 2-Amino-5-phosphonovalerate
  • Atropine
  • Kynurenic Acid
  • Pentobarbital
  • Pyridostigmine Bromide
  • Tubocurarine