M-type potassium current （IM） was initially isolated from sympathetic neurons in 1980 and named as it was inhibited by muscarine. In 1998, the molecular identity of M-current was revealed to be heterotetramers of KCNQ2 and KCNQ3 subunits, whose mutations cause neonatal epilepsy. Reduction of voltage-gated KCNQ2/3 K＋ channel （M-channel） activity leads to neuronal byperexcitability that defines the fundamental mechanism of neurological disorders such as epilepsy and pain. Thus, suppression of neuronal hyperexcitability by activation of KCNQ2/3 channels serves the basis for development of the channel openers for treatment of epilepsy and pain. The well-known KCNQ opener is retigabine （Potiga） that was approved by FDA as an antiepileptic drug in 2011. Recent studies also provide evidence that KCNQ2/3 channel openers are effective in animal models of bipolar disorder, anxiety and schizophrenia, whereas KCNQ2/3 inhibitors, on the other hand, are indicated for improvement of learning and memory in animal models. We recently designed and validated a novel series of pyrazolo [1,5-a]pyrimidin-7（4H）-ones （PPOs） that selectively activate KCNQ2/3 and show antiepileptic and analgesic activity in vivo. Up to date, all the progress made enforces the view that targeting voltage-gated KCNQ/M-channel may provide therapeutic potential for treatment of neuropsychiatric disorders.
A simple, reliable and efficient assay for quantitative analysis of a novel Kv7/KCNQ/M-channel opener QO58-lysin in rat plasma was developed using high-performance liquid chromatography（HPLC） with UV detection. Separation of compound QO58-lysin from plasma was achieved using a reverse-phase C18 column with a mobile phase of 0.2 M ammonium acetate in H2O–acetonitrile（40：60, v/v） with nitrendipine used as an internal standard（IS）. The retention times of QO58-lysin and the IS in rat plasma were 3.8 and 5.4 min, respectively. Calibration curve was linear ranging from 0.1 to 120 μg/mL with correlation coefficient（r2） of 0.9996. The lower limit of quantification was 0.1 μg/mL. Accuracy, precision, recovery as well as stability were all within acceptable criteria according to Food and Drug Administration（FDA） guidelines. This validated assay was successfully applied to determine the pharmacokinetics of QO58-lysin administered intravenously（10 mg/kg） in SD rats. The distribution and elimination half-life of QO58-lysin in plasma was（0.25±0.16） h and（2.15±0.12） h, respectively.
