钡离子和四乙铵对皮层神经元的影响。

Effects of Ba2+ and tetraethylammonium on cortical neurones.

Krnjević K, Pumain R, Renaud L

J Physiol. 1971 May;215(1):223-45. doi: 10.1113/jphysiol.1971.sp009466.

Abstract

Ba(2+), applied by micro-iontophoresis, excites most cortical neurones that are excitable by ACh; other neurones tend to be depressed.2. The discharges evoked by Ba(2+) resemble those evoked by ACh, but they have an even slower time course and are characterized by firing in high frequency bursts.3. The excitatory action of Ba(2+), unlike that of ACh, is not abolished by muscarine antagonists; but it can be prevented with dinitrophenol.4. The depolarizing effect of Ba(2+) is associated with a rise in membrane resistance and it has a reversal level 24 mV more negative than the resting potential.5. These observations suggest that, as in other tissues, Ba(2+) reduced the K(+) conductance by a direct action on the cell membrane. Some diminution in Na(+) inactivation is indicated by the repetitive firing at high frequency.6. TEA has a predominantly depressant effect on all neurones tested. Like Ba(2+), it often increases greatly the duration of spikes, but there is no regular change in resting membrane resistance and no tendency to repetitive firing. TEA probably reduces only the delayed K(+) current.7. Even in large doses neither Ba(2+) nor TEA interferes with the conductance increase that generates the typical prolonged IPSPs recorded in cortical neurones.

摘要

通过微离子电泳施加的钡离子（Ba²⁺）可兴奋大多数能被乙酰胆碱（ACh）兴奋的皮层神经元；其他神经元则倾向于被抑制。
钡离子（Ba²⁺）诱发的放电类似于乙酰胆碱（ACh）诱发的放电，但它们的时间进程更慢，其特征是高频爆发式放电。
与乙酰胆碱（ACh）不同，钡离子（Ba²⁺）的兴奋作用不会被毒蕈碱拮抗剂消除；但它可被二硝基苯酚阻止。
钡离子（Ba²⁺）的去极化作用与膜电阻增加有关，其反转电位比静息电位负24 mV。
这些观察结果表明，与其他组织一样，钡离子（Ba²⁺）通过直接作用于细胞膜降低了钾离子（K⁺）电导。高频重复放电表明钠离子（Na⁺）失活有所减少。
四乙铵（TEA）对所有测试的神经元主要起抑制作用。与钡离子（Ba²⁺）一样，它常常极大地增加动作电位的持续时间，但静息膜电阻没有规律性变化，也没有重复放电的倾向。四乙铵（TEA）可能仅降低延迟钾离子电流。
即使大剂量使用，钡离子（Ba²⁺）和四乙铵（TEA）都不会干扰在皮层神经元中记录到的典型延长抑制性突触后电位（IPSPs）所产生的电导增加。