[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.
Zheng
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QA
Higashi
H
H
Inokuchi
H
H
Nishi
S
S
D000818:Animals; D008297:Male; D008564:Membrane Potentials; D008636:Mesencephalon / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D014278:Trigeminal Nuclei / Q000502:physiology*