Continuous determination of Na concentration in CSF during recovery from thermal dehydration in rats.

为了确定热脱水恢复过程中脑脊液（[Na]csf）中Na浓度的变化，我们开发了一种双管钠敏感电极连续测量大鼠[Na]csf的方法。通过固定离子交换剂（Bis - 12-crown-4）制备了钠敏感膜。测定Na浓度的置信限在生理范围内<正负0.5 meq/kg H20。我们将电极放置在麻醉大鼠的右侧脑室，使其热脱水约为身体重量的11%。血浆中的钠浓度（[Na]p）通过放置在左颈动脉和右颈静脉之间的体外旁路回路中的流动细胞型钠敏感电极来测量。我们在注射2.5 ml/ lOOg体wt蒸馏水10分钟和注射结束20分钟后连续测量[Na]p和[Na]csf的变化。[Na]p在给药后3 min开始下降，在给药结束后6 min达到最低值-11.6<±>0.9 meq/kg H_2O。该水平一直维持到实验结束。[Na]csf在开始输注后下降缓慢，实验结束时变化为-5.9<正- >0.5 meq/kg H_2O。为了评估脱水大鼠血液和脑脊液中水和/或钠离子运动的变化，我们比较了脱水(D)和脱水(E)大鼠[Na]esf对[Na]p变化的反应时间。E组反应时间5.3<正负>0.6 min，显著大于D组，2.0<正负>0.5 min（p<0.01）。这些结果表明[Na]csf对急性[Na]p变化的反应减弱和延迟，并且在补液过程中比[Na]p恢复得更慢。此外。在补液过程中，血液和脑脊液之间的水和/或钠的运动加速。

To determine changes in Na concentration in the cerebrospinal fluid([Na]csf)during restitution from thermal dehydration, we developed a method to measure[Na]csf continuously in rats using a double barreled Na sensitive electrode. The Na sensitive membrane was prepared by immobilizing an ionexchanger(Bis 12-crown-4). The confidence limit for measuring Na concentration was <plus-minus>0.5 meq/kg H20 within physiological range. We placed the electrode in the right lateral ventricle of an anesthetized rat thermally dehydrated by about 11% of body wt. Na concentration in plasma([Na]p)was measured by a flow cell typed Na sensitive electrode placed in an extracorporeal by-pass circuit between the left carotid artery and right jugular vein. We measured changes in[Na]p and[Na]csf continuously during the infusion of 2.5 ml/ lOOg body wt of distilled water for 10 min and following 20 min after the end of infusion. [Na]p began to decrease 3 min after the start of infusion and attained the lowest value of -11.6<plus-minus>0.9 meq/kg H_2O at 6 min after the end of infusion. This level was maintained until the end of experiment. [Na]csf decreased slowly after the start of infusion and at the end of experiment the change was -5.9<plus-minus>0.5 meq/kg H_2O. To assess the change in water and/or Na ion movement between blood and CSF in dehydrated rats, the response time of[Na]esf to change in[Na]p was compared between dehydrated(D)and enhydrated rats(E). The response time in E was 5.3<plus-minus>0.6 min which was significantly larger than in D, 2.0<plus-minus>0.5 min(p<0.01). These results suggest that[Na]csf showed attenuated and delayed response against acute change in[Na]p and recovered more slowly than[Na]p during rehydration. In addition. the movement of water and/or Na between blood and CSF was accelerated during rehydration.