Melatonin enhances the excitability of rod-on bipolar cells by inhibiting TEA-sensitive potassium channels in rat retina
会议名称：《中国生理学会第23届全国会员代表大会暨生理学学术大会》
会议日期：2010年
学科分类：1001[医学-基础医学(可授医学、理学学位)] 10[医学]
摘 要：By challenging specific receptors,melatonin synthesized and released by photoreceptors regulates various physiological functions in vertebrate *** this work,we studied modulatory effects of melatonin on rod-ON bipolar cells(BCs) and the underlying mechanisms using the whole-cell patch-clamp techniques in rat retinal *** the current-clamp mode,extracellular application of melatonin induced a significant membrane depolarization, which was reversed by the MT receptor antagonist *** the other hand,in the voltage-clamp mode, melatonin did not induce any current and intracellular application of cGMP or 8-Br-cGMP failed to induce currents in BCs,unlike our previous observation in carp retinal BCs that melatonin induces a remarkable cGMP-dependent inward cation *** experiments showed that outward potassium currents of BCs consisted of two components:tetraethylammol/Lonium(TEA)- and 4-aminopyridine(4-AP)-sensitive *** of melatonin selectively inhibited the TEA-sensitive current component but did not show any effects on the 4-AP-sensitive *** melatonin effect was blocked by co-application of ***,application of the phospholipase C(PLC) inhibitor U73122 or the PKC inhibitor bisindolylmaleimideⅣ(BisⅣ) eliminated the melatonin *** the Ca chelator BAPTA-containing pipette was used,melatonin failed to inhibit the K currents. Neither PKA nor PKG seemed to be involved because both the PKA inhibitor Rp-cAMP and the PKG inhibitor KT5823 did not block the melatonin-induced suppression of the K *** consequence,we conclude that by activating G-protein coupled MT receptors,melatonin could enhance the excitability of ON-BCs by inhibiting TEA-sensitive K ***-dependent PLC-PKC signaling pathway is involved in the melatonin effect.