脊髄活動性の一分析法

An Analytical Method of the Activity of the Spinal Cord

　脊髄の活動性の分析は，細胞内電極法の導入により更に詳細に行う事が可能になつた^2）3）。然しながら，脊髄機能の活動性を考察する際，個々の神経細胞の状態よりは寧ろ全体の統合機能の変化が興味の対象となる場合が多い。脊髄統合機能の典型的な一例は，屈筋と伸筋支配に関するfunctional reciprocityに於て示された^12）。この事実に基き，屈筋と伸筋を支配する前角運動ニューロンの活動性を同時に同種のparameterを以て比較分析する事を，本実験に於て試みた。この分析法は，また脊髄介在ニューロンの活動性の変化の推測にも適用出来る。脊髄の活動性を薬理的に変化させた場合，その薬物の作用場が，運動ニューロンであるか或は介在ニューロンにあるかを検討する事が，この分析法の第二の目的である。

　Monosynaptic reflex responses were simultaneously recorded from flexor and extensor motor nerves in the cat following stimulation of distally cut dorsal roots. The reflex response was expressed relative to amplitude of response given by discharge of the total motoneuron pool. Each flexor monosynaptic reflex response was plotted as a function of the extensor monosynaptic reflex response which was simultaneously recorded. When about 25 reflex responses were successively obtained, the distribution of points in such analytical diagram varied considerably in different preparations, being dependent upon the condition of the spinal cord. The analysis was made in decerebrate animals, acute and chronic spinal cats and under administration of gammaaminobutyric acid. It was concluded that a horizontal shift of the points in the analytical diagram is attributable to a selective change in the internuncial activity and that a shift of the points along a slope of 45 degrees is due to a selective change of the motoneuron activity.