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

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Abstract

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 μM) 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 μM. The potentiation produced by spermine was somewhat greater at positive potentials. The onset of potentiation was fast (t 1 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.

Original languageEnglish (US)
Pages (from-to)107-112
Number of pages6
JournalNeuroscience Letters
Volume152
Issue number1-2
DOIs
StatePublished - Apr 2 1993

Keywords

  • Glutamate receptor
  • Potentiation
  • Spermidine
  • Spermine

ASJC Scopus subject areas

  • Neuroscience(all)

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