Oliet S H, Bourque C W
Centre for Research in Neuroscience, Montreal General Hospital, Quebec, Canada.
Am J Physiol. 1993 Dec;265(6 Pt 2):R1475-9. doi: 10.1152/ajpregu.1993.265.6.R1475.
Whole cell patch-clamp recordings were obtained from isolated rat supraoptic nucleus magnocellular neurosecretory cells (MNCs). Under current clamping, hyperosmolality produced by the addition of 10-30 mM mannitol depolarized each of 25 cells tested. In contrast, reducing fluid osmolality from 295 to 265 mosmol/kgH2O had the reverse effect, hyperpolarizing 18 of 21 MNCs. Voltage-clamp recordings in 43 cells revealed that the effects of hypo- and hyperosmolality, respectively, were caused by decreases and increases in a nonselective cation conductance reversing near -41 mV. Current-voltage analysis in Na(+)-free solution revealed that the reversal potentials of currents elicited by increases and decreases in osmolality both shifted to a value near -90 mV, suggesting that a single ionic conductance is modulated by these stimuli. The relation between cationic conductance and osmolality was specific, sensitive (+2.14%.mosmol-1.kgH2O-1), and well-fit by linear regression (r = 0.96; n = 22 cells) between 275 and 325 mosmol/kgH2O. These results indicate that MNCs express a depolarizing current that is active under steady-state conditions and that the up- or downregulation of this current contributes to the excitation or inhibition of these cells upon acute exposure to hypo- or hyperosmolar conditions.
全细胞膜片钳记录是从分离的大鼠视上核大细胞神经分泌细胞（MNCs）获得的。在电流钳制下，添加10 - 30 mM甘露醇产生的高渗使25个受试细胞中的每一个都发生去极化。相反，将液体渗透压从295 mosmol/kgH2O降至265 mosmol/kgH2O则产生相反的效果，使21个MNCs中的18个发生超极化。对43个细胞的电压钳记录显示，低渗和高渗的影响分别是由一种在-41 mV附近反转的非选择性阳离子电导的降低和增加引起的。在无钠溶液中的电流 - 电压分析表明，渗透压升高和降低所引发电流的反转电位均移至接近-90 mV的值，这表明单一离子电导受这些刺激调节。在275至325 mosmol/kgH2O之间，阳离子电导与渗透压之间的关系具有特异性、敏感性（+2.14%·mosmol-1·kgH2O-1），并且通过线性回归拟合良好（r = 0.96；n = 22个细胞）。这些结果表明，MNCs表达一种在稳态条件下活跃的去极化电流，并且该电流的上调或下调有助于这些细胞在急性暴露于低渗或高渗条件时的兴奋或抑制。
