Effects of polyamines on NMDA-induced currents in rat hippocampal neurons: a whole-cell and single-channel study

Neurosci Lett. 1993 Apr 2;152(1-2):107-12. doi: 10.1016/0304-3940(93)90495-7.


Actions of the polyamines spermine and spermidine on NMDA-induced currents were examined in cultured hippocampal neurons from embryonic rat. In whole-cell patch experiments using voltage-clamp, spermine (300 microM) produced about a two-fold potentiation of responses to NMDA (at -70 mV in the presence of saturating glycine); half-maximal potentiation was elicited at 207 microM. The potentiation produced by spermine was somewhat greater at positive potentials. The onset of potentiation was fast (t1/2 < 1 s), indicative of an extracellular site of action. Spermidine was of comparable potency but less efficacious than spermine in potentiating NMDA responses. In excised outside-out patches, spermine exhibited two actions on NMDA-induced single-channel responses. In some patches, it increased the channel open probability; both frequency of channel opening and burst length were increased with no significant change in the mean open duration, which accounted for much of the potentiation seen in whole-cell experiments. In all patches, spermine decreased channel conductance at negative voltages, an effect ascribable to fast channel block (with a possible contribution by charge screening). These results are consistent with opposing actions of polyamines mediated at distinct sites on the NMDA receptor.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials / drug effects*
  • Animals
  • Cells, Cultured
  • Drug Synergism
  • Hippocampus / drug effects*
  • Ion Channel Gating / drug effects
  • N-Methylaspartate / pharmacology*
  • Neurons / drug effects*
  • Neurons / physiology
  • Rats
  • Spermidine / pharmacology*
  • Spermine / pharmacology*


  • Spermine
  • N-Methylaspartate
  • Spermidine