Block of native Ca(2+)-permeable AMPA receptors in rat brain by intracellular polyamines generates double rectification

J Physiol. 1995 Jul 15;486 ( Pt 2)(Pt 2):305-12. doi: 10.1113/jphysiol.1995.sp020813.


1. The influence of intracellular factors on current rectification of different subtypes of native alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate receptors (AMPARs) was studied in rat brain slices by combining fast application of glutamate with patch pipette perfusion. 2. The peak current-voltage (I-V) relation of the AMPARs expressed in Bergmann glial cells of cerebellum and dentate gyrus (DG) basket cells of hippocampus was weakly rectifying in outside-out patches and nystatin-perforated vesicles, but showed a doubly rectifying shape with a region of reduced slope between 0 and +40 mV in nucleated patches. The I-V relation of AMPARs expressed in hippocampal CA3 pyramidal neurones was linear in all recording configurations. 3. Intracellular application of 25 microM spermine, a naturally occurring polyamine, blocked outward currents in outside-out patches from Bergmann glial cells and DG basket cells in a voltage-dependent manner, generating I-V relations with a doubly rectifying shape which were similar to those recorded in nucleated patches. AMPARs in CA3 pyramidal cell patches were unaffected by 25 microM spermine. 4. The half-maximal blocking concentration of spermine at +40 mV was 0.3 microM in Bergmann glial cell patches and 1.5 microM in DG basket cell patches, whereas it was much higher (>> 100 microM) for CA3 pyramidal cell patches. Spermidine also affected current rectification, but with lower affinity. The block of outward current by polyamines following voltage jumps developed within < 0.5 ms. 5. We conclude that current rectification, rather than being an intrinsic property of the Ca(2+)-permeable AMPAR channel, is generated by polyamine block.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / cytology
  • Brain / metabolism*
  • Calcium / metabolism*
  • Electrophysiology
  • Intracellular Membranes / metabolism
  • Kinetics
  • Patch-Clamp Techniques
  • Permeability
  • Polyamines / metabolism*
  • Rats
  • Rats, Wistar
  • Receptors, AMPA / antagonists & inhibitors*


  • Polyamines
  • Receptors, AMPA
  • Calcium