痙性斜頸様姿勢と脳内モノアミン—化学的VMT破壊ネコにおける研究

EXPERIMENTAL STUDY FOR THE SPASMODIC TORTICOLLISLIKE POSTURE BY CHEMICAL LESIONING IN THE VENTROMEDIAL TEGMENTUM (VMT) IN CATS

I．はじめに

　ヒトの痙性斜頸のなかには，瞳孔不同や，Benedictの症候群を伴うなど，中脳被蓋の病変の存在も示唆する症例があり^17），またサル^2,9,18）やネコ^{12,15,16,22）}においても一側の中脳腹側被蓋部（VMT）を破壊すると同じような異常姿勢の起こることが報告されている。

　一方，Parkinsonismをはじめ不随意運動を主徴とする疾患と，脳内モノアミンとの関連が近年注目されているVMTはこれらモノアミンの線維の密な束が上行しているところ^23）であつて，動物実験においては，ドーパミンニューロン（DAニューロン）と，セロトニンニューロン（5—HTニューロン）のいずれが主に傷害を受けるかにより，異なつた頭頸部の異常姿勢や運動が発現する^12,16）との報告もあり，Moriら^16）や石川^12）はDAニューロンが頭部の側屈運動（lateral bending）に，5—HTニューロンが回旋運動（rotary movement around longi—tudinal axis）^14）に主に関与すると述べている。しかしこれら一連の研究においては，ネコの一側のVMTの通電破壊が行なわれているため，非モノアミン性ニューロンの同時破壊をさけることができないうらみがあつた。

Neurotoxic agents were injected into the one side of ventromedial tegmentum (VMT) in cats.

In cases to which 5, 6-dihydoroxytryptamine (5, 6-DHT) or 6-hydroxydopamine (6-OHDA) plus 5, 6-DHT were injected, a depletion of both 5-hydro-xytryptamine (5-HT) and dopamine (DA) in the unilateral caudate nucleus and cortex cerebri was observed and these animals displayed circus move-ment and lateral bending of the neck towards the side of the chemical lesion for a short period after the operation.

A simple injection of 5, 7-DHT in the VMT in-duced a marked depletion of 5-HT in the caudate nucleus withous showing a definite decrease in DA. These animals did not show any abnormal neck movement nor head posture, except one case in which typical spasmodic torticollislike posture was observed and in which non-specfic destructive lesion due to bleeding was revealed in the VMT area similar to that observed by the electrocoagulation.

In cats with unilateral depletion of 5-HT in the caudate nucleus, intraperitoneal injection of L-5- HTP produced spasmodic torticollislike head move-ment of a minor degree with other abnormal posture of the extremities, but L-DOPA did not.

In the neurotoxic lesion, a mutual compensatory mechanism between DA and 5-HT would be rapid as compared with those observed in the electro-coagulative lesion. These mutual compensation would play at the level within the caudate nucleus and also between the caudate nucleus and the cerebral cortex.

From the data described above, the author pointed out that for the manifestation of spasmodic tor-ticollis-like posture, especially rotary movement on the head, destruction of non-monoaminergic fibre (s) in the VMT might be indispensable. Monoami-nergic fibre will be acting as a modulator for an enhancement of the abnormal movement.