title: Diclofenac, a nonsteroidal anti-inflammatory drug, activates the transient outward K+ current in rat cerebellar granule cells.
abstract: Diclofenac, a nonsteroidal anti-inflammatory drug (NSAID), has been widely investigated in terms of its pharmacological action, but less is known about its direct effect on ion channels. Here, the effect of diclofenac on voltage-dependent transient outward K+ currents (I(A)) in cultured rat cerebellar granule cells was investigated using the whole-cell voltage-clamp technique. At concentrations of 10(-5)-10(-3) M, diclofenac reversibly increased the I(A) amplitude in a dose-dependent manner and significantly modulated the steady-state inactivation properties of the I(A) channels, but did not alter the steady-state activation properties. Furthermore, diclofenac treatment resulted in a slightly accelerated recovery from I(A) channel inactivation. Intracellular application of diclofenac could mimic the effects induced by extracellular application, although once the intracellular response reached a plateau, extracellular application of diclofenac could induce further increases in the current. These observations indicate that diclofenac might exert its effects on the channel protein at both the inner and outer sides of the cell membrane. Our data provide the first evidence that diclofenac is able to activate transient outward potassium channels in neurons. Although further work will be necessary to define the exact mechanism of diclofenac-induced I(A) channel activation, this study provides evidence that the nonsteroidal anti-inflammatory drug, diclofenac, may play a novel neuronal role that is worthy of future study.
authors.affiliation: Center for Brain Science Research, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai 200433, PR China.
authors.forename: Lin-Yun
authors.initials: LY
authors.lastname: Liu
authors.forename: Xiao-Wei
authors.initials: XW
authors.lastname: Fei
authors.forename: Zhao-Ming
authors.initials: ZM
authors.lastname: Li
authors.forename: Zhi-Hong
authors.initials: ZH
authors.lastname: Zhang
authors.forename: Yan-Ai
authors.initials: YA
authors.lastname: Mei
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D004008:Diclofenac / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000187:drug effects* / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D015221:Potassium Channels / Q000187:drug effects* / Q000528:radiation effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D015221:Potassium Channels; D004008:Diclofenac