Effects of pregabalin on the activity of glutamate transporter type 3

Pregabalin, (S)-3-aminomethyl-5-methyl hexanoic acid, is a ligand for the 2 subunit (a component of voltage-gated calcium channels) and has analgesic and anticonvulsant properties. Glutamate uptake by glutamate transporters may be a mechanism for these properties. We investigated the effects of pregabalin on the activity of the neuronal glutamate transporter type 3 (EAAT3). EAAT3 was expressed in Xenopus laevis oocytes. Two-electrode voltage clamping was used to record membrane currents before, during, and after applying l-glutamate (30 M) in the presence or absence of pregabalin. Currents were also measured in oocytes pretreated with a protein kinase C (PKC) activator (phorbol-12-myristate-13-acetate, PMA), PKC inhibitors (chelerythrine or staurosporine), or a phosphatidylinositol-3-kinase (PI3K) inhibitor wortmannin. The exposure of the oocytes injected with EAAT3 mRNA to serial concentrations of pregabalin (0.0660 M) significantly increased their responses to 30 M l-glutamate. A kinetic study showed that pregabalin significantly increased V-max without changing K-m. Treatment of oocytes with PMA, pregabalin, or pregabalin plus PMA significantly increased transporter currents vs controls, but treatment with PMA plus pregabalin did not increase the responses further vs PMA or pregabalin alone. In addition, pretreatment of oocytes with two PKC inhibitors (chelerythrine or staurosporine), or inhibitor wortmannin, significantly reduced basal and pregabalin-enhanced EAAT3 activity. Pregabalin increased EAAT3 activity and PKC and PI3K were involved. This may explain the analgesic effect of pregabalin in neuropathic pain.