title: Gabapentin inhibits the activity of the rat excitatory glutamate transporter 3 expressed in Xenopus oocytes.
abstract: Gabapentin, a derivative of γ-aminobutyric acid (GABA), is used to treat epilepsy and neuropathic pain. The pharmacological mechanisms for gabapentin effects are not completely elucidated. We investigated the effect of gabapentin on the activity of excitatory amino acid transporter 3 (EAAT3) that can regulate extracellular glutamate concentrations. EAAT3 was expressed in Xenopus oocytes. Membrane currents were recorded after application of l-glutamate in the presence or absence of different concentrations of gabapentin (1-300μM) by using a two-electrode voltage clamp. To determine the effect of gabapentin on Vmax and Km of EAAT3 for l-glutamate, l-glutamate at 3-300μM was used. To study the effects of protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) on gabapentin-induced changes in EAAT3 activity, oocytes were incubated with the PKC activator (Phorbol 12-myristate 13-acetate, PMA), the PKC inhibitors (chelerythrine or staurosporine), and the PI3K inhibitor wortmannin. Gabapentin decreased EAAT3 activity in a concentration-dependent manner and EAAT3 activity was significantly inhibited by 10-300μM gabapentin. Gabapentin significantly decreased Vmax without affecting Km. PMA increased EAAT3 activity; however, gabapentin attenuated the PMA-induced increase in EAAT3 activity. Pre-incubation of oocytes with chelerythrine, staurosporine, or wortmannin decreased basal EAAT3 activity, which was further reduced by gabapentin. We conclude that gabapentin decreases EAAT3 activity at clinically relevant and higher concentrations, in which PKC and PI3K may not be involved. The results suggest that EAAT3 might not be a target for the anticonvulsant action of gabapentin.
authors.affiliation: Department of Anesthesiology and Pain medicine, Bestian Hospital, Seoul 939-24, Republic of Korea.
authors.forename: Yang Sook
authors.initials: YS
authors.lastname: Gil
authors.affiliation: Department of Anesthesiology and Pain medicine, School of Medicine, Ewha Womans University, Seoul 158-710, Republic of Korea.
authors.forename: Jong Hak
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain medicine, School of Medicine, Ewha Womans University, Seoul 158-710, Republic of Korea.
authors.forename: Chi Hyo
authors.initials: CH
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain medicine, School of Medicine, Ewha Womans University, Seoul 158-710, Republic of Korea.
authors.forename: Jong In
authors.initials: JI
authors.lastname: Han
authors.affiliation: Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA 22903, USA.
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Zuo
authors.affiliation: Department of Anesthesiology and Pain medicine, School of Medicine, Ewha Womans University, Seoul 158-710, Republic of Korea. Electronic address: baikhj@ewha.ac.kr.
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Baik
mesh_terms: D000588:Amines / Q000494:pharmacology*; D000818:Animals; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D050580:Excitatory Amino Acid Transporter 3 / Q000037:antagonists & inhibitors* / Q000235:genetics*; D005260:Female; D000077206:Gabapentin; D015870:Gene Expression; D009865:Oocytes / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D014982:Xenopus laevis / Q000235:genetics*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D000588:Amines; D003509:Cyclohexanecarboxylic Acids; D050580:Excitatory Amino Acid Transporter 3; D000077206:Gabapentin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D005680:gamma-Aminobutyric Acid
keywords: (L)-glutamate (PubChem CID: 33032); Chelerythrine (PubChem CID: 2703); Excitatory amino acid transporter 3; Gabapentin; Gabapentin (PubChem CID: 3446); Glutamate; Phorbol 12-myristate 13-acetate (PubChem CID: 27924); Phosphatidylinositol 3-kinase; Protein kinase C; Staurosporine (PubChem CID: 44259); Wortmannin (PubChem CID: 312145)