The Protective Effect Of New Kv7 Potassium Channel Openers On Diseases Associated With Hyperexcitation Of Neurons

Voltage-gated Kv7/KCNQ/M-potassium channels are widely expressed in the central nervous system and peripheral nervous systems.Kv7 channels play an essential role in control of membrane potential and neuronal excitability.Changes of neuronal excitability are associated with a variety of diseases,such as epilepsy,pain and anxiety.The development of new opener targeting Kv7 channels will provide a potential treatment for these neurological diseases.Objective: To evaluate the effect of novel Kv7 potassium channel openers SCR2682,SCR2673 and SCR2692 on Kv7 channels,and study the anticonvulsant,analgesic and antianxiety effects in order to provide preliminary experimental basis for the development of novel Kv7 potassium channel openers.Methods: 1.The activation of SCR2682,SCR2673 and SCR2692 on Kv7.2/7.3 channels and the effect of SCR2682 on hippocampal neurons excitability were evaluated by whole cell patch clamp technique.2.The electroconvulsive model was prepared to evaluate the anticonvulsant effect of SCR compounds.The mice were divided into control group,retigabine(RTG,7 mg/kg)group,SCR2682(0.25,0.5,1 and 2 mg/kg)group,SCR2682(2 mg/kg)+ Kv7 channel inhibitor XE991(3 mg/kg)group,SCR2673(0.5,1 and 2 mg/kg)group and SCR2692(0.5,1,2 and 4 mg/kg)group.3.The inflammatory pain was induced by Complete Freund’s Adjuvant(CFA).Rats were randomly divided into control group,model group,RTG(7 mg/kg)group,SCR2682(0.5,1 and 2 mg/kg)group,SCR2673(0.5,1 and 2 mg/kg)group and SCR2692(0.5,1 and 2 mg/kg)group.The hindpaw withdraw latency and mechanical force threshold were measured after 30 min,1 h,2 h,3 h administration of drugs to evaluate the analgesic effect of SCR compounds.4.In the open field test,the mice were randomly divided into control group,RTG(10 mg/kg)group and SCR2682(05,1,2,4 and 8mg/kg)group to evaluate the spontaneous activities.5.In the mice marble burying and elevated plus maze tests,the mice were randomly divided into control group,RTG(10 mg/kg)group,SCR2682(0.5,1,2 mg/kg)group and SCR2682(2 mg/kg)+ XE991(1 mg/kg)group.The number of marbles burried and the time ratio in the open arm were recorded to evaluate the antianxiety effect of SCR2682.Results: 1.The results of whole-cell patch clamp recordings showed that SCR2682,SCR2673 and SCR2692 activated Kv7.2/7.3,and SCR2682 significantly increased M current and reduced the excitability of hippocampal neurons.2.In the maximal electroshock study,all mice in control group experienced the maximal electroconvulsive episodes.The mice administrated with 0.25,0.5,1 and 2 mg/kg SCR2682 showed 44.77%,66.67%,88.89% and 100% protection,while 10 mg/kg RTG showed 66.67% protection.The mice administrated with SCR2682 showed dosedependent protection.SCR2682(0.25 mg/kg)and XE991(3 mg/kg)showed only 33.33% protection.0.5,1 and 2 mg/kg SCR2673 showed 50%,66.67% and 100% protection respectively.0.5,1,2 and 4 mg/kg SCR2692 showed 33.33%,40%,93.33% and 100% protection respectively.These results indicated that SCR2682,SCR2673 and SCR2692 showed anticonvulsive effect.3.24 h after injection of CFA,the rats were hypersensitive to mechanical and thermal stimuli.Compared with the model group,SCR2682(0.5,1 and 2 mg/kg)increased the paw withdrawal thermal latency and mechanical threshold.SCR2673 reduced sensitivity to thermal stimulation at two concentrations(1 and 2 mg/kg).SCR2692(2 mg/kg)reduced sensitivity to thermal stimulation.As a positive control,RTG(7 mg/kg)also increased the paw withdrawal thermal latency and mechanical threshold.These results indicated that SCR2682,SCR2673 and SCR2692 showed analgesic effect.4.In open field test,RTG(10 mg/kg)and SCR2682 at doses of 0.5,1 and 2 mg/kg did not alter the spontaneous activity of mice,while the total distance and average speed of mice were reduced after administration of SCR2682 at doses of 4 and 8 mg/kg compared with the mice in control group.5.In the mice marble burying testing,both SCR2682(0.5,1 and 2 mg/kg)and RTG(10 mg/kg)reduced the number of marbles buried by mice and SCR2682 showed dosedependence characteristic.However,SCR2682(2 mg/kg)+ XE991(1 mg/kg)significantly increased the number of buryied marbles compared with SCR2682(2 mg/kg)alone group.In the elevated plus maze test,SCR2682(0.5,1 and 2 mg/kg)and RTG(10 mg/kg)increased the proportion of time in the open arm of mice.These results indicated that SCR2682 showed antianxiety effect.Conclusion: SCR2682,SCR2673 and SCR2692 activate Kv7.2/7.3 channels and show pharmacological effects of anticonvulsion,analgesia and antianxiety in animal experiments.