Removal of KCNQ2 from parvalbumin-expressing interneurons improves anti-seizure efficacy of retigabine.

Anti-seizure drug (ASD) targets are widely expressed in both excitatory and inhibitory neurons. It remains unknown if the action of an ASD upon inhibitory neurons could counteract its beneficial effects on excitatory neurons (or vice versa), thereby reducing the efficacy of the ASD. Here, we examine whether the efficacy of the ASD retigabine (RTG) is altered after removal of the Kv7 potassium channel subunit KCNQ2, one of its drug targets, from parvalbumin-expressing interneurons (PV-INs). Parvalbumin-Cre (PV-Cre) mice were crossed with Kcnq2-floxed (Kcnq2fl/fl) mice to conditionally delete Kcnq2 from PV-INs. In these conditional knockout mice (cKO, PV-Kcnq2fl/fl), RTG (10 mg/kg, i.p.) significantly delayed the onset of either picrotoxin (PTX, 10 mg/kg, i.p)- or kainic acid (KA, 30 mg/kg, i.p.)-induced convulsive seizures compared to vehicle, while RTG was not effective in wild-type littermates (WT). Immunostaining for KCNQ2 and KCNQ3 revealed that both subunits were enriched at axon initial segments (AISs) of hippocampal CA1 PV-INs, and their specific expression was selectively abolished in cKO mice. Accordingly, the M-currents recorded from CA1 PV-INs and their sensitivity to RTG were significantly reduced in cKO mice. While the ability of RTG to suppress CA1 excitatory neurons in hippocampal slices was unchanged in cKO mice, its suppressive effect on the spike activity of CA1 PV-INs was significantly reduced compared with WT mice. In addition, the RTG-induced suppression on intrinsic membrane excitability of PV-INs in WT mice was significantly reduced in cKO mice. These findings suggest that preventing RTG from suppressing PV-INs improves its anticonvulsant effect.

High Yield of Screening for ADHD in the Epilepsy Monitoring Unit.

Objective: ADHD is common in patients with epilepsy, but adult patients with possible epilepsy are not routinely screened for ADHD. We aimed to characterize the results of two validated screening tools in the setting of an Epilepsy Monitoring Unit (EMU). Method: This study utilized the validated Adult ADHD Self-Report Scale version 1.1 (ASRS) and Conners Continuous Performance Test, third edition (CPT-III) to screen patients who were admitted to the EMU at a Level 4 epilepsy center. Patients with epileptic seizures (ES) were compared with patients with psychogenic nonepileptic seizures (PNES). Results: In all, 40.6% of patients screened positive using the ASRS. A significantly greater proportion of patients with PNES (63.6%) screened positive compared with patients with ES (27.8%, Fisher's exact test, p = .005). Positive ASRS screens showed no significant association with positive CPT screens (chi-square test, p = .146). Conclusion: Adult patients admitted to the EMU are at a high risk of comorbid attention deficits.