Pharmacological inhibition of the Na+/Ca2+ exchanger enhances depolarizations induced by oxygen/glucose deprivation but not responses to excitatory amino acids in rat striatal neurons

Paolo Calabresi, Girolama A. Marfia, Salvatore Amoroso, Antonio Pisani, Giorgio Bernardi

Research output: Contribution to journalArticle

Abstract

Background and Purpose - Neuronal Na+/Ca2+ exchanger plays a relevant role in maintaining intracellular Ca2+ and Na+ levels under physiological and pathological conditions. However, the role of this exchanger in excitotoxicity and ischemia-induced neuronal injury is still controversial and has never been studied in the same neuronal subtypes. Methods - We investigated the effects of bepridil and 3',4'-dichlorobenzamil (DCB), 2 blockers of the Na+/Ca2+ exchanger, in rat striatal spiny neurons by utilizing intracellular recordings in brain slice preparations to compare the action of these drugs on the membrane potential changes induced either by oxygen and glucose deprivation (OGD) or by excitatory amino acids (EAAs). Results - Bepridil (3 to 100 μmol/L) and DCB (3 to 100 μmol/L) caused a dose-dependent enhancement of the OGD-induced depolarization measured in striatal neurons. The EC50 values for these effects were 31 μmol/L and 29 μmol/L, respectively. At these concentrations neither bepridil nor DCB altered the resting membrane properties of the recorded cells (membrane potential, input resistance, and current-voltage relationship). The effects of bepridil and DCB on the OGD-induced membrane depolarization persisted in the presence of D-2-amino-5-phosphonovalerate (50 μmol/L) plus 6-cyano-7- nitroquinoxaline-2,3-dione (20 μmol/L), which suggests that they were not mediated by an enhanced release of EAAs. Neither tetrodotoxin (1 μmol/L) nor nifedipine (10 μmol/L) affect the actions of these 2 blockers of the Na+/Ca2+ exchanger, which indicates that voltage-dependent Na+ channels and L-type Ca2+ channels were not involved in the enhancement of the OGD- induced depolarization. Conversely, the OGD-induced membrane depolarization was not altered by 5-(N,N-hexamethylene) amiloride (1 to 3 μmol/L), an inhibitor of the Na+/H+ exchanger, which suggests that this antiporter did not play a prominent role in the OGD-induced membrane depolarization recorded from striatal neurons. Bepridil (3 to 100 mmol/L) and DCB (3 to 100 μmol/L) did not modify the amplitude of the excitatory postsynaptic potentials evoked by cortical stimulation. Moreover, these blockers did not affect membrane depolarizations caused by brief applications of glutamate (0.3 to 1 mmol/L), AMPA (0.3 to 1 μmol/L), and NMDA (10 to 30 μmol/L). Conclusions - These results provide pharmacological evidence that the activation of the Na+/Ca2+ exchanger exerts a protective role during the early phase of OGD in striatal neurons, although it does not shape the amplitude and the duration of the electrophysiological responses of these cells to EAA.

Original languageEnglish
Pages (from-to)1687-1694
Number of pages8
JournalStroke
Volume30
Issue number8
Publication statusPublished - Aug 1999

Keywords

  • 3,4-dichlorobenzamil
  • Bepridil
  • Excitatory amino acids
  • Ischemia
  • Rats
  • Sodium- hydrogen antiporter
  • Synaptic transmission

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Neuroscience(all)

Fingerprint Dive into the research topics of 'Pharmacological inhibition of the Na+/Ca2+ exchanger enhances depolarizations induced by oxygen/glucose deprivation but not responses to excitatory amino acids in rat striatal neurons'. Together they form a unique fingerprint.

  • Cite this