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  • Title: Cellular mechanism of action of cognitive enhancers: effects of nefiracetam on neuronal Ca2+ channels.
    Author: Yoshii M, Watabe S, Murashima YL, Nukada T, Shiotani T.
    Journal: Alzheimer Dis Assoc Disord; 2000; 14 Suppl 1():S95-102. PubMed ID: 10850736.
    Abstract:
    Cellular mechanisms underlying the cognition-enhancing actions of piracetam-like nootropics were studied by recording Ca2+ channel currents from neuroblastoma x glioma hybrid (NG108-15) cells and Xenopus oocytes expressing Ca2+ channels. In NG108-15 cells, nefiracetam (1 microM) produced a twofold increase in L-type Ca2+ channel currents. A similar, but slightly less potent effect was observed with aniracetam, whereas piracetam and oxiracetam exerted no such effects. Cyclic AMP analogs mimicked the nefiracetam action. N-type Ca2+ channel currents inhibited by leucine (Leu)-enkephalin by means of inhibitory G proteins (Go/Gi) were recovered promptly by nefiracetam, whereas those inhibited by prostaglandin E1 via stimulatory G proteins were not affected by nefiracetam. Cells treated with pertussis toxin (500 ng/mL, > 20 hours) were insensitive to nefiracetam. In Xenopus oocytes functionally expressing N-type (alpha1B) Ca2+ channels and delta-opioid receptors, nefiracetam was also effective in facilitating the recovery from Leu-enkephalin-induced inhibition. These results suggest that nefiracetam, and possibly aniracetam, may activate N- and L-type Ca2+ channels in a differential way depending on how they recover from Go/Gi-mediated inhibition.
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