脳定常電位の発生機序

THE ORIGIN OF STATIONARY POTENTIAL OF THE BRAIN

Ｉ．はじめに

　脳の直流電位の定常成分，すなわち定常電位Station—ary potential （SPと略す）は，イヌ・ネコで＋10mV，ヒトでは＋20mV程度の電位であり，その頭皮上分布の測定により頭蓋内器質的疾患の診断が可能なことは，すでに発表した通りである^15,16,22）。本論文の目的はこのSPの発生機序を究明することにある。

　脳の直流電位について論ずる場合，このSPと緩変動電位slowly changing potential （SCPと略す）を厳密に分けて考えないと大きな混乱を招く^22）。SCPに関しては従来までにも色々な研究がなされてきた。その発生機序については今のところ次のような3つの有力な説がある。

To clarify the origin of Stationary Potential (SP), the stationary component of DC potential of the brain which was defined by Sano and is about 10 mV in cats and dogs and 20 mV in human, the following experiments were carried out in 35 cats, 12 dogs and 7 rats anesthetized with Nembutal, paralyzed with Gallamine and ventilated mechanic-cally. The first experiment was intended to verify the existence of SP in the retina which is the simplest model of the central nervous system, and liver and glioma of C57BL mouse which contains no neuron. The second one was to examine whether the blood brain bareir (BBB) which supposed by Tschirgi 1958 to be responsible forchanges of DC potential by pH shift of the brain or blood generates SP or not. The third one was to study the relationship between SP and the membrane potential of the neuron or glia. Results.

1. The retina has SF of 3-4 mV in vivo and in vitro, whereas the liver and glioma of C57BL mouse has no such SF. These results indicate that glia is not responsible the SP. (See Fig. 1-3).

2. The BBB is not the generator of SP. (See Fig. 5-7).

3. After rapid lowering of SP due to asphyxia, the resting membrane potential of the neuron disappears similtaneously, but that of the glial celldoes not. (see Fig. 8). Not only these results but also clinical and other experimental observations indicate that SP should be reflecting the resting membrane potential of neuron.

If SP depends upon the membrane potential of neurons, it is postulated that the SP is originated from the hypothetical open dipole layers which consist of the cell membrane and the opposite myelinated, long axons. (See Fig. 9). The mathe-matical estimation exhibits that the value of SP in human is 14.9 mV, that approximates the value obtained by actual mesurement.