title: Synaptic and extrasynaptic GABA transporters as targets for anti-epileptic drugs.
abstract: Inhibition of the GABA transporter subtype GAT1 by the clinically available anti-epileptic drug tiagabine has proven to be an effective strategy for the treatment of some patients with partial seizures. In 2005, the investigational drug EF1502 was described as possessing activity at both GAT1 and BGT-1. When combined with the GAT1 selective inhibitor tiagabine, EF1502 was found to possess a synergistic anti-convulsant action in the Frings audiogenic seizure-susceptible mouse model of reflex epilepsy. This effect was subsequently attributed to inhibition of BGT-1. In this study, the anti-convulsant effect of the GAT2/3 inhibitor SNAP-5114 was assessed in the Frings audiogenic seizure-susceptible mouse alone, and in combination with tiagabine and EF1502. The results showed that SNAP-5114 produced a synergistic anti-convulsant effect in combination with EF1502 but not when used in combination with tiagabine. These findings support anatomical evidence that GAT2/3 are most likely located at the synapse in close proximity to GAT1; whereas BGT-1 is located some distance away from the synapse and GAT1 and GAT2/3. Lastly, EF1502 and tiagabine were evaluated alone, and in combination, in the corneal kindled mouse model of partial epilepsy. The results of this evaluation provide further evidence in support of a role for BGT-1 in the control of seizure activity. In addition, they suggest that the combined inhibition of GAT1 and BGT-1 may afford some advantage over inhibiting either transporter alone.
authors.affiliation: Department of Pharmacology and Pharmacotherapy, Faculty of Pharmaceutical sciences, University of Copenhagen, Denmark.
authors.forename: Karsten K
authors.initials: KK
authors.lastname: Madsen
authors.forename: Rasmus P
authors.initials: RP
authors.lastname: Clausen
authors.forename: Orla M
authors.initials: OM
authors.lastname: Larsson
authors.forename: Povl
authors.initials: P
authors.lastname: Krogsgaard-Larsen
authors.forename: Arne
authors.initials: A
authors.lastname: Schousboe
authors.forename: H Steve
authors.initials: HS
authors.lastname: White
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D000840:Anisoles / Q000494:pharmacology; D000927:Anticonvulsants / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D003315:Cornea / Q000502:physiology; D005260:Female; D018755:GABA Agonists / Q000494:pharmacology; D050485:GABA Plasma Membrane Transport Proteins / Q000187:drug effects* / Q000378:metabolism*; D007696:Kindling, Neurologic / Q000187:drug effects; D008297:Male; D051379:Mice; D018696:Neuroprotective Agents / Q000494:pharmacology; D009557:Nipecotic Acids / Q000494:pharmacology; D012640:Seizures / Q000517:prevention & control; D013569:Synapses / Q000187:drug effects* / Q000378:metabolism*; D000078308:Tiagabine
chemical_list: C092337:1-(2-(tris(4-methoxyphenyl)methoxy)ethyl)-3-piperidinecarboxylic acid; D000840:Anisoles; D000927:Anticonvulsants; D002352:Carrier Proteins; D018755:GABA Agonists; D050485:GABA Plasma Membrane Transport Proteins; D018696:Neuroprotective Agents; D009557:Nipecotic Acids; C490439:Slc6a12 protein, mouse; C493419:Slc6a13 protein, mouse; C072207:betaine plasma membrane transport proteins; D000078308:Tiagabine