Abstract
Benzodiazepine compounds are widely used in clinical situations as somnifacient, antianxiety and antiepileptic drugs by acting at GABAa receptors in the central nervous system. On the other hand, the neural stem cells (NSCs) with self-renewal and multipoietic activities are recently found to exist in adult mammalian brain and seem to play some physiological roles. However, it is still unknown whether benzodiazepine affects NSCs functions. Therefore, we examined the effect of diazepam on the proliferative activity of cultured murine NSCs and the expression of GABAa receptor mRNA and GABA synthesizing enzymes (GAD) mRNA. The NSCs derived from the striatum of E15.5 mice were cultured by neurosphere method using EGF-containing medium. The proliferative activity of NSCs was examined by WST-8 assay and BrdU incorporation assay in the presence of EGF (20 ng/ml). The abundant expressions of GABAa receptor mRNA and GAD-65 and -67 mRNAs were measured by RT-PCR using specific primer sets. We found that diazepam suppressed EGF-induced proliferation in a concentration-dependent manner. GABAa receptor agonist, muscimol, also decreased NSCs proliferation. The expression of GABAa receptor alpha1 subunit mRNA as well as GAD-65 or -67 mRNAs were observed in the cultured NSCs. These results suggest that NSCs proliferation is regulated by GABAa receptor systems, which are activated by GABA autocreinally secreted from NSCs themselves. [Jpn J Physiol 54 Suppl:S225 (2004)]
