Dendritic glutamate receptor channels in rat hippocampal CA3 and CA1 pyramidal neurons

J Physiol. 1995 Jan 15;482 ( Pt 2)(Pt 2):325-52. doi: 10.1113/jphysiol.1995.sp020521.


1. Properties of dendritic glutamate receptor (GluR) channels were investigated using fast application of glutamate to outside-out membrane patches isolated from the apical dendrites of CA3 and CA1 pyramidal neurons in rat hippocampal slices. CA3 patches were formed (15-76 microns from the soma) in the region of mossy fibre (MF) synapses, and CA1 patches (25-174 microns from the soma) in the region of Schaffer collateral (SC) innervation. 2. Dual-component responses consisting of a rapidly rising and decaying component followed by a second, substantially slower, component were elicited by 1 ms pulses of 1 mM glutamate in the presence of 10 microM glycine and absence of external Mg2+. The fast component was selectively blocked by 2-5 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and the slow component by 30 microM D-2-amino-5-phosphonopentanoic acid (D-AP5), suggesting that the fast and slow components were mediated by the GluR channels of the L-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and NMDA type, respectively. The peak amplitude ratio of the NMDA to AMPA receptor-mediated components varied between 0.03 and 0.62 in patches from both CA3 and CA1 dendrites. Patches lacking either component were rarely observed. 3. The peak current-voltage (I-V) relationship of the fast component was almost linear, whereas the I-V relationship of the slow component showed a region of negative slope in the presence of 1 mM external Mg2+. The reversal potential for both components was close to 0 mV. 4. Kainate-preferring GluR channels did not contribute appreciably to the response to glutamate. The responses to 100 ms pulses of 1 mM glutamate were mimicked by application of 1 mM AMPA, whereas 1 mM kainate produced much smaller, weakly desensitizing currents. This suggests that the fast component is primarily mediated by the action of glutamate on AMPA-preferring receptors. 5. The mean elementary conductance of AMPA receptor channels was about 10 pS, as estimated by non-stationary fluctuation analysis. The permeability of these channels to Ca2+ was low (approximately 5% of the permeability to Cs+). 6. The elementary conductance of NMDA receptor channels was larger, with a main conductance state of about 45 pS. These channels were 3.6 times more permeable to Ca2+ than to Cs+.(ABSTRACT TRUNCATED AT 400 WORDS)

Publication types

  • Comparative Study

MeSH terms

  • 2-Amino-5-phosphonovalerate / pharmacology
  • 6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
  • Animals
  • Calcium / metabolism
  • Cell Membrane Permeability
  • Dendrites / chemistry
  • Dendrites / physiology*
  • Electric Conductivity
  • Hippocampus / cytology*
  • Hippocampus / physiology*
  • Kainic Acid / pharmacology
  • Magnesium / pharmacology
  • Patch-Clamp Techniques
  • Pyramidal Cells / physiology
  • Rats
  • Rats, Wistar
  • Receptors, AMPA / antagonists & inhibitors
  • Receptors, AMPA / drug effects
  • Receptors, AMPA / physiology*
  • Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors
  • Receptors, N-Methyl-D-Aspartate / drug effects
  • Receptors, N-Methyl-D-Aspartate / physiology*
  • Time Factors
  • Zinc / pharmacology
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / pharmacology


  • Receptors, AMPA
  • Receptors, N-Methyl-D-Aspartate
  • 6-Cyano-7-nitroquinoxaline-2,3-dione
  • 2-Amino-5-phosphonovalerate
  • alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
  • Magnesium
  • Zinc
  • Kainic Acid
  • Calcium