三叉神经中脑核神经元膜的电学特性

用大鼠脑干脑片,给三叉神经中脑核79个神经元作了细胞内记录,测算了20个神经元膜的电学特性:静息电位-60.3±5.6mV;输入阻抗为10.5±5.4MΩ;时间常数1.3±0.5ms。电刺激可诱发动作电位,测算32个神经元的有关参数:阈电位-50—-55mV;波幅69.5±6.1mV;超射11.9±3.6mV;波宽0.8±0.2ms。TTX(0.3μmol/L)或无钠使之消失。通以长时程矩形波电流可引起200—250Hz的2—15个重复放电,但在通电停止前终止,TEA或4-AP可延长放电。膜电位-60—-55mV时在动作电位之后可看到阈下电位波动,它不受TTX的影响,无钙时消失,TEA或4-AP使波幅增大。静息电位去极化可使45个神经元中的40个发生外向整流作用,并被TEA,4-AP或无钙抑制,超极化则发生内向整流作用,Cs或无钠抑制之。灌流液中加入各种钾通道阻断药时神经元的稳态I-V曲线发生相应变化,提示I_(DR),l_A,I_(K(Ca))及I_Q可能都与静息时的膜电导有关。

ELECTRICAL MEMBRANE PROPERTIES OF NEURONES OF MESENCEPHALIC NUCLEUS OF FIFTH NERVE IN RATS

Intracellular recordings were made from 79 neurones in the mesencephalic nucleus of fifth nerve (MNV) contained within rat brain stem slice preparation in vitro. The electrical membrane characteristics of 20 neurones among them were measured. The resting membrane potential, input resistance and membrane time constant of MNV neurones were -60.3 +/- 5.6 mV, 10.5 +/- 5.4M omega and 1.3 +/- 0.5 ms respectively. No action potential occurred spontaneously at resting membrane potential. The action potential was elicited by application of a depolarizing rectangular pulse to the neuron. The data of 32 MNV neurones action potentials showed that the threshold potentials ranged from -50 mV to -55 mV, the duration of the spike was 0.8 +/- 0.2 ms and the amplitude of the spike was 69.5 +/- 6.1 mV with an overshoot of 11.9 +/- 3.6 mV. The action potential disappeared reversibly by perfusion of Na-free solution or TTX (0.3 mumol/L) added in Krebs solution. The repetitive discharge was elicited by a long lasting depolarizing rectangular pulse applied to the neuron, its frequency was 200-250 Hz at the beginning of the pulse and disappeared before the ending of the pulse. The repetitive discharge usually consists of 2-15 spikes. The halfway disappearance of the repetitive discharge was prevented by TEA or 4-AP. The subthreshold potential oscillation followed the action potential at membrane potential -60(-)-55 mV, and this potential oscillation was not affected by TTX, but it was abolished by perfusion of Ca-free solution. However, its amplitude was increased by TEA or 4-AP. When the resting membrane potential was depolarized, the outward rectification in 40 among 45 MNV neurones was seen, which was inhibited by TEA, 4-AP or Ca-free perfusion. On the other hand, the inward rectification was seen when the resting membrane potential was hyperpolarized, which was inhibited by Cs ion or Na-free perfusion. When the blockers of K channels were added into Krebs solution, the steady state I-V relationship of the neurones was changed correspondingly. It is suggested that the IDR, IA, IK(Ca), and IQ are related to the resting membrane conductances.