脳幹を経由する大内臓神経—運動反射について

STUDIES ON A SPLANCHNIC-MOTOR REFLEX HAVING ITS REFLEX CENTER IN THE BRAIN STEM

Ｉ．はじめに

　内臓疾患のさいに腹壁の筋緊張が増加し，筋性防御defénse musculaireが生ずることはよく知られている。この現象は内臓神経からの求心性インパルスが，反射性に腹壁の筋に達して現われたものとみなされ，内臓—運動反射viscero-motor reflexとよばれている^{3）11）12）}。

　その反射の機序に関しては，脊髄ネコについて，大内臓神経の電気刺激による種々の運動神経からの反射電位を導出し，脊髄固有性反射としての脊髄内経路が解析された^5）。

An attempt has been made on 88 chloralose anesthetized cats to analyse the mechanism of a splanchnic-motor reflex which is supposed to have its reflex center mainly in the medulla in comparison with that of the propriospinal reflex.

1) Two kinds of reflex responses, the early one with a short reflex time (abbreviated ER) and the late one with a long reflex time (LR), were observed in the intercostal nerves as well as in the ventral roots (Th 1~Th 12) on the either sides following electrical stimulation of the greater splanchnic nerve.

2) As to the ER, the longer the distance of the spinal segment sending the ventral root under examination from the Th 10 segment, the longer the reflex time. Whereas the LR showed shorterreflex time as the ventral root under examination ascends higher from the Th 10 segment, until the ER and LR became fused at the cervical level.

3) It was considered that the nerve fibers in the intercostal nerve eliciting the ER and LR are res-pectively mainly Aβ and Aγδ groups judging from their thresholds of the stimulations and the evoked responses thereby.

4) The ER as well as LR obtained in the inter-costal nerves were eliminated or markedly depressed following transection of the ipsilateral dorsal root at the same segment.

5) The average conduction velocity in the spinal cord was 17. 2m/sec in the case of the ER and 28. 6m/sec for descending in the case of the LR.

6) Judging from the results of intercollicular decerebration, cervical spinal transection, Nembutal administration, asphyxiation etc., it was supposed that the ER is a propriospinal reflex and the LR is a reflex, the reflex center of which is located in the brain stem mainly in the medulla.

7) Reflex potentials elicited likewise in the nerve of the four limbs and also the physiological mean-ing of the LR were discussed.