The mRNA levels of NKCC1, an inwardly directed Na + , K + -2Cl − cotransporter that facilitates the accumulation of intracellular Cl − , and of KCC2, an outwardly directed K + -Cl − cotransporter that extrudes Cl − , were studied in surgically resected brain specimens from drug-resistant temporal lobe (TL) epilepsy (TLE) patients. Quantitative RT-PCR analyses of the mRNAs extracted from the human TLE-associated brain regions revealed an up-regulation of NKCC1 mRNA and a down-regulation of KCC2 mRNA in the hippocampal subiculum, compared with the hippocampus proper or the TL neocortex, suggesting an abnormal transcription of Cl − transporters in the TLE subiculum. In parallel experiments, cell membranes isolated from the same TLE-associated brain regions were injected into Xenopus oocytes that rapidly incorporated human GABA A receptors into their surface membrane. The GABA currents elicited in oocytes injected with membranes from the subiculum had a more depolarized reversal potential ( E GABA ) compared with the hippocampus proper or the neocortex. The NKCC1 blocker bumetanide or a temperature decrease of 10°C shifted the GABA-current E GABA more negative in oocytes injected with membranes from TLE hippocampal subiculum, matching the E GABA of TL neocortex-injected oocytes. We conclude that the anomalous expression of both Cl − transporters, KCC1 and NKCC2, in TLE hippocampal subiculum probably causes altered Cl − transport in the “epileptic” neurons, as revealed in the microtransplanted Xenopus oocytes, and renders GABA aberrantly “exciting,” a feature that may contribute to the precipitation of epileptic seizures.

1. The recently isolated compound methyllyeaconitine (MLA) is a plant toxin which is a competitive inhibitor of nicotinic acetylcholine receptors (nAChRs). We found that homomeric a7 receptors display a very high sensitivity to MLA with an IC50 in the picomolar range. 2. The competitive nature of the a7 MLA blockade was reinforced by the observation that this compound has no action on wild-type serotoninergic receptors (5-HT3), whereas it is a powerful antagonist of chimaeric receptors a7-5-HT3. 1992;Drasdo, Caulfield, Bertrand, Bertrand & Wonnacott, 1992; Wonnacott, Albuquerque & Bertrand, 1993;Puchacz, Buisson, Bertrand & Lukas, 1994;Gopalakrishnan et al. 1995). The nicotinic acetylcholine receptors form a rather wide family whose members display quite distinct features either from the point of view of their patterns of expression or from their physiological and pharmacological properties (for reviews see Role, 1992;Clarke, 1993;Sargent, 1993;Galzi & Changeux, 1994;Lindstrom, 1995). In vertebrates, a-BuTX is a competitive antagonist of muscle nAChR, alflly8 or alfllye, and of homomeric neuronal nAChRs, a7, a8, a9, whereas all the other neuronal receptors formed by the assembly of a2, a3, c4 subunits with the non-a subunits (fl2 and /14) are completely insensitive to a-BuTX (for reviews see Role,

A large body of evidence that has accumulated over the past decade strongly supports the role of inflammation in the pathophysiology of human epilepsy. Specific inflammatory molecules and pathways have been identified that influence various pathologic outcomes in different experimental models of epilepsy. Most importantly, the same inflammatory pathways have also been found in surgically resected brain tissue from patients with treatment-resistant epilepsy. New anti-seizure therapies may be derived from these novel potential targets. An essential and crucial question is whether targeting these molecules and pathways may result in anti-ictogenesis, anti-epileptogenesis and/or disease-modification effects. Therefore, preclinical testing in models mimicking relevant aspects of epileptogenesis is needed to guide integrated experimental and clinical trial designs. We discuss the most recent preclinical proof-of-concept studies validating a number of therapeutic approaches against inflammatory mechanisms in animal models that could represent novel avenues for drug development in epilepsy. Finally, we suggest future directions to accelerate preclinical to clinical translation of these recent discoveries.

The properties of ␥-aminobutyric acid (GABA) type A receptors (GABA A receptors) microtransplanted from the human epileptic brain to the plasma membrane of Xenopus oocytes were compared with those recorded directly from neurons, or glial cells, in human brains slices. Cell membranes isolated from brain specimens, surgically obtained from six patients afflicted with drug-resistant temporal lobe epilepsy (TLE) were injected into frog oocytes. Within a few hours, these oocytes acquired GABA A receptors that generated GABA currents with an unusual run-down, which was inhibited by orthovanadate and okadaic acid. In contrast, receptors derived from membranes of a nonepileptic hippocampal uncus, membranes from mouse brain, or recombinant rat ␣1␤2␥2-GABA receptors exhibited a much less pronounced GABA-current rundown. Moreover, the GABA A receptors of pyramidal neurons in temporal neocortex slices from the same six epileptic patients exhibited a stronger run-down than the receptors of rat pyramidal neurons. Interestingly, the GABA A receptors of neighboring glial cells remained substantially stable after repetitive activation. Therefore, the excessive GABA-current run-down observed in the membrane-injected oocytes recapitulates essentially what occurs in neurons, rather than in glial cells. Quantitative RT-PCR analyses from the same TLE neocortex specimens revealed that GABA Areceptor ␤1, ␤2, ␤3, and ␥2 subunit mRNAs were significantly overexpressed (8-to 33-fold) compared with control autopsy tissues. Our results suggest that an abnormal GABA-receptor subunit transcription in the TLE brain leads to the expression of run-down-enhanced GABA A receptors. Blockage of phosphatases stabilizes the TLE GABAA receptors and strengthens GABAergic inhibition. It may be that this process can be targeted to develop new treatments for intractable epilepsy.temporal lobe epilepsy ͉ microtransplantation into Xenopus oocyte ͉ okadaic acid ͉ ␥-aminobutyric acid-current run-down ͉ human tissue slices