FLUPIRTINE PROTECTS NEURONS AGAINST EXCITOTOXIC OR ISCHEMIC DAMAGE AND INHIBITS THE INCREASE IN CYTOSOLIC CA2+ CONCENTRATION

We tested the effect of flupirtine against ischemic and excitotoxic ne uronal damage as well as on the glutamate-induced rise in cytosolic ca lcium ion concentration (= [Ca2+](i)). For in vivo experiments we used a model of focal cerebral ischemia in mice. The middle cerebral arter y was permanently occluded and 48 h afterwards brain tissue was staine d with neutral red, perfusion-fixed and the infarct surface was determ ined planimetrically. Pretreatment with flupirtine significantly reduc ed the infarct area (controls: 24.3 +/- 4.8 mm(2), 1 mg/kg flupirtine: 20.1 +/- 3.6 mm(2) and 10 mg/kg flupirtine: 19.5 +/- 3.9 mm(2); P < 0 .05), whereas postischemic application of flupirtine failed to reduce the infarct area. For in vitro studies, primary neuronal cultures were prepared from the hippocampi of newborn rats and excitotoxic damage w as induced by exposing the cells to 500 mu M L-glutamate for 30 min. W e could demonstrate that flupirtine (1-10 mu M) was capable of protect ing neurons against glutamate-induced cytotoxicity. In order to elucid ate the underlying mechanism of action, we tested the effect of flupir tine on the glutamate-induced rise in [Ca2+](i) using the Ca2+-indicat or fura-2. L-Glutamate added in a final concentration of 100 mu M to t he cultured cells for 16 s caused a rise in [Ca2+](i) from about 100 n M to 900 nM. Flupirtine (0.1-10 mu M) reduced the glutamate-induced ri se in [Ca2+](i), concentration dependently.