Activation of mGluR5 induces spike afterdepolarization and enhanced excitability in medium spiny neurons of the nucleus accumbens by modulating persistent Na+ currents

Marcello D'Ascenzo, Maria Vittoria Podda, Tommaso Fellin, Gian Battista Azzena, Philip Haydon, Claudio Grassi

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)

Abstract

The involvement of metabotropic glutamate receptors type 5 (mGluR5) in drug-induced behaviours is well-established but limited information is available on their functional roles in addiction-relevant brain areas like the nucleus accumbens (NAc). This study demonstrates that pharmacological and synaptic activation of mGluR5 increases the spike discharge of medium spiny neurons (MSNs) in the NAc. This effect was associated with the appearance of a slow afterdepolarization (ADP) which, in voltage-clamp experiments, was recorded as a slowly inactivating inward current. Pharmacological studies showed that ADP was elicited by mGluR5 stimulation via G-protein-dependent activation of phospholipase C and elevation of intracellular Ca2+ levels. Both ADP and spike aftercurrents were significantly inhibited by the Na+ channel-blocker, tetrodotoxin (TTX). Moreover, the selective blockade of persistent Na+ currents (I-NaP), achieved by NAc slice pre-incubation with 20 nm TTX or 10 mu m riluzole, significantly reduced the ADP amplitude, indicating that this type of Na+ current is responsible for the mGluR5-dependent ADP. mGluR5 activation also produced significant increases in I-NaP, and the pharmacological blockade of this current prevented the mGluR5-induced enhancement of spike discharge. Collectively, these data suggest that mGluR5 activation upregulates I-NaP in MSNs of the NAc, thereby inducing an ADP that results in enhanced MSN excitability. Activation of mGluR5 will significantly alter spike firing in MSNs in vivo, and this effect could be an important mechanism by which these receptors mediate certain aspects of drug-induced behaviours.
Original languageEnglish
Pages (from-to)3233-3250
Number of pages18
JournalTHE JOURNAL OF PHYSIOLOGY
Volume587 (13)
DOIs
Publication statusPublished - 2009

Keywords

  • METABOTROPIC GLUTAMATE-RECEPTOR
  • RAT SUPRAOPTIC NUCLEUS
  • RESPIRATORY RHYTHM GENERATION

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