Topiramate protects against glutamate- and kainate-induced neurotoxicity in primary neuronal–astroglial cultures

Abstract

Potential neuroprotective effects of the antiepileptic drug (AED) topiramate (TPM) were evaluated using primary neuronal–astroglial cultures or astroglial-enriched cultures from newborn rats exposed to excitotoxic concentrations of glutamate (Glu) or kainate. Neurons expressed functional Glu receptors of the NMDA and AMPA/kainate types as evaluated by immunocytochemistry and Ca 2+ imaging. When Glu (10 mM) was added to 9–10-day cultures incubated with the fluorescent dye calcein/AM for 5 h, there was a marked cell loss in both culture types, but was more pronounced in the neuronal–astroglial cultures. When TPM (5–10 μM) was included in the medium together with Glu, the amount of surviving cells was significantly higher in the neuronal–astroglial cultures, but not in the astroglial-enriched cultures. Immuno-labeling of the cultures revealed an enhanced survival of MAP positive neuronal cells when TPM was included in the Glu containing medium. As TPM has a proven negative modulatory effect on kainate activated receptors, neuronal–astroglial cultures were further exposed to excitotoxic concentrations of kainate (100 μM) and analyzed immunohistochemically. Significantly more MAP positive neurons survived in the TPM containing medium and showed a morphology similar to untreated cells. Valproate and phenytoin were used as reference AEDs. In conclusion, our results demonstrate a protective effect of TPM upon neuronal cells in primary culture, exposed to excitotoxic levels of Glu or kainate.