Thomas G R, Duncan G, Sanderson J
Department of Cell Biology and Physiology, School of Biological Sciences, University of East Anglia, Norwich, United Kingdom.
Invest Ophthalmol Vis Sci. 1998 Jan;39(1):111-9.
Factors that interfere with the acetylcholine signaling system have long been implicated in cataract. The authors sought to investigate the nature of the electrical response of the intact rabbit lens to acetylcholine.
Membrane potential (Vm) and electrical conductance (Gm) were monitored in the isolated, perifused lens by a technique utilizing two internal microelectrodes.
Acetylcholine (100 nM to 1 mM) induced a decrease in membrane conductance and a depolarization of membrane potential in the intact lens. The responses were reversed by application of the muscarinic antagonist, atropine (1 microM to 100 microM). In the presence of 1 microM thapsigargin and 30 microM cyclopiazonic acid, acetylcholine still induced an electrical response. Long exposures to acetylcholine induced sustained oscillations of Vm in 10 of 29 lenses (34%). Oscillations were blocked by atropine and the L-type Ca2+ channel blocker nifedipine (10 microM) but were potentiated by thapsigargin.
The rabbit lens expressed muscarinic receptors that when activated modulate ionic conductances and cause membrane potential oscillations throughout the tissue. Ca2+ influx rather than primary release from intracellular stores appeared to play a major role in the oscillatory response to acetylcholine.
长期以来，干扰乙酰胆碱信号系统的因素一直被认为与白内障有关。作者旨在研究完整兔晶状体对乙酰胆碱的电反应性质。
采用双内微电极技术监测离体灌注晶状体的膜电位（Vm）和电导（Gm）。
乙酰胆碱（100 nM至1 mM）可使完整晶状体的膜电导降低，膜电位去极化。毒蕈碱拮抗剂阿托品（1 microM至100 microM）可逆转这些反应。在存在1 microM毒胡萝卜素和30 microM环匹阿尼酸的情况下，乙酰胆碱仍可诱导电反应。长时间暴露于乙酰胆碱可使29个晶状体中的10个（34%）出现Vm的持续振荡。振荡被阿托品和L型钙通道阻滞剂硝苯地平（10 microM）阻断，但被毒胡萝卜素增强。
兔晶状体表达毒蕈碱受体，激活后可调节离子电导并导致整个组织的膜电位振荡。钙离子内流而非细胞内储存的钙的初次释放似乎在对乙酰胆碱的振荡反应中起主要作用。
