Glutamate induced astroglial swelling--methods and mechanisms

Glutamate (Glu) plays an important role in the early development of brain injuries caused by ischemia, i.e. stroke, or brain trauma. Glu induces a rapid astroglial swelling which, in turn, deranges the composition of neuroactive substances in the extracellular space. We report that Glu can induce astroglial cell swelling by interaction with metabotropic Glu receptors (mGluRs). Furthermore, the Na(+)-K(+)-2Cl- cotransporter, a Na(+)-K(+) ATPase, and the Na(+)-dependent electrogenic Glu carrier seem to be involved in this Glu-induced astroglial cell swelling. Two methods for studying cell swelling arc described. One is based on variations in the signal emitted by the fluorescent probe fura-2/AM when excited at its isosbestic point. These variations were shown to be directly proportional to variations in intracellular volume. Relative changes in cell volume and intracellular calcium concentration could be detected simultaneously in single astroglial cells. The other method used permits the cell volume to be calculated in relative terms with the aid of image processing techniques.