Methamphetamine induces a rapid increase of intracellular Ca ++ levels in neurons overexpressing GCaMP 5

In this study, methamphetamine ( M eth)‐ and glutamate ( G lu)‐mediated intracellular Ca ++ ( Ca ++ i ) signals were examined in real time in primary cortical neurons overexpressing an intracellular Ca ++ probe, GCaMP5 , by adeno‐associated viral ( AAV ) serotype 1. Binding of Ca ++ to GCaMP increased green fluorescence intensity in cells. Both M eth and G lu induced a rapid increase in Ca ++ i , which was blocked by MK 801, suggesting that M eth enhanced Ca ++ i through G lu receptor in neurons. The M eth‐mediated Ca ++ signal was also blocked by Mg ++ , low Ca ++ or the L ‐type Ca ++ channel inhibitor nifedipine. The ryanodine receptor inhibitor dantrolene did not alter the initial Ca ++ influx but partially reduced the peak of Ca ++ i . These data suggest that M eth enhanced Ca ++ influx through membrane Ca ++ channels, which then triggered the release of Ca ++ from the endoplasmic reticulum in the cytosol. AAV ‐ GCaMP 5 was also injected to the parietal cortex of adult rats. Administration of M eth enhanced fluorescence in the ipsilateral cortex. Using immunohistochemistry, M eth‐induced green fluorescence was found in the NeuN ‐containing cells in the cortex, suggesting that M eth increased Ca ++ in neurons in vivo . In conclusion, we have used in vitro and in vivo techniques to demonstrate a rapid increase of Ca ++ i by M eth in cortical neurons through overexpression of GCaMP 5. As M eth induces behavioral responses and neurotoxicity through Ca ++ i , modulation of Ca ++ i may be useful to reduce M eth‐related reactions.