発作波に伴う緩電位変動の検討—焦点部における皮質内変動と細胞発射の相関

BASIC MECHANISM OF STEADY POTENTIAL CHANGES ASSOCIATED WITH ECoG PAROXYSMS: SIMULTANEOUS RECORDING OF SP AND NEURONAL ACTIVITIES

I．はじめに

　脳の電気現象のうち，最近，緩電位変動（Steady po—tential shift，あるいは佐野^21）のslowly changing po—　tential）が注目され，この方面の研究報告も多く，脳の機能解明の有力な手掛りとなつている。しかし，その発現機序，本態となると，ニューロン説，グリア説など種々の意見があり，一致が見られていない。

　私は，ネコの脳表にペニシリンを塗布し，実験てんかん焦点を作製，脳波上のparoxysmに伴う皮質内局所の緩電位変動とニューロン活動（細胞外導出）の同時記録を行ない，両者を対比検討することにより，緩電位変動の本態に関し若干の考察を行なつた。

The relationship of steady potential (SP) shiftsassociated with Penicillin-induced ECoG paroxysmsand extra-cellularly recorded unitary activities wasstudied in the pericruciate gyrus in cat.

1) Even in the early stage when SP shifts onthe cortical surface associated with isolated ECoGspikes were less prominent, definite negative SPshifts were observed in the cortical layers.

2) In the advanced stage, negative SP shifts wererecorded both on the surface and in the corticallayers. Maximum amplitude of the negative shiftswere noted 1000-1500 μ beneath the surface.

3) In the stage of spike-after-discharges and tonic-clonic sustained paroxysms, negative SP shifts werealso noted in the cortical layers.

4) There existed two types of negative SP shiftsin coincidence with isolated ECoG spikes in thecortical layers ; one was negative shift with slowafter negativity and the other was negative shiftfollowed by another negative aftermath.

5) Of special interest was the fact that highfrequency neuronal discharges were noted only inthe early phase of negative SP shifts, and cessationof unit firings occurred during the period of slowafter negativity and the second negative aftermath.

6) Similar dissociation between SP shifts andunitary activities was evident in the ECoG parox-ysms of spike-after-discharges and tonic-clonic ictalevents.

7) These data suggested that early phase ofnegative SP shifts associated with ECoG paroxysmsreflected neuronal activities, but that dissociationsof two measures presumably reflected current,generated secondarily to neuronal discharges (e.g.glial membrane potentials).