Osmolarity, ionic flux, and changes in brain excitability

Philip A Schwartzkroin, Scott C. Baraban, Daryl W. Hochman

Research output: Contribution to journalArticle

160 Scopus citations

Abstract

The majority of modern epilepsy research has focused on possible abnormalities in synaptic and intrinsic neuronal properties - as likely epileptogenic mechanisms as well as the targets for developing novel antiepileptic treatments. However, many other processes in the central nervous system contribute to neuronal excitability and synchronization. Regulation of ionic balance is one such set of critical processes, involving a complex array of molecules for moving ions into and out of brain cells - both neurons and glia. Alterations in extracellular-to-intracellular ion gradients can have both direct and indirect effects on neuronal discharge. We have found, for example that when hippocampal slices are exposed to hypo- osmotic bathing medium, the cells not only swell, but there is also a significant increase in the amplitude of a delayed rectifier potassium current in inhibitory interneurons - an effect that may contribute to the increase in tissue excitability associated with hypo-osmolar treatments. In contrast, antagonists of the chloride co-transporter, furosemide or bumetanide, block epileptiform activity in both in vitro and in vivo preparations. This antiepileptic effect is presumably due to the drugs' ability to block chloride co-transport. Indeed, prolonged tissue exposure to low levels of extracellular chloride have a parallel action. These experiments indicate that manipulation of ionic balance may not only facilitate epileptiform activities, but may also provide insight into new therapeutic strategies to block seizures.

Original languageEnglish (US)
Pages (from-to)275-285
Number of pages11
JournalEpilepsy Research
Volume32
Issue number1-2
DOIs
StatePublished - Sep 1 1998
Externally publishedYes

Keywords

  • Chloride co-transport
  • Furosemide
  • Hypo- osmolarity
  • Ionic regulation
  • Potassium currents

ASJC Scopus subject areas

  • Clinical Neurology
  • Pediatrics, Perinatology, and Child Health
  • Neurology

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