犬の脳血管の神経支配（形態学的研究）—cholinergic nerveを中心に

A HISTOCHEMICAL STUDY ON THE INNERVATION OF CEREBRAL BLOOD VESSELS IN THE DOG : WITH SPECIAL REGARD TO THE CHOLINERGIC NERVES

Ⅰ．はじめに

　脳の血管に神経が存在することは，1664年にすでにThomas Willisが報告しており，1836年にPurkingeがWillis輪の動脈に伴つた神経線維を発見している^19,22）しかし，組織学的に無髄神経線維が軟膜動脈に随伴することを報告したのはStöhr （1928），Hassin（1930）らであるという^4）。その後，サル，ネコ，ウサギ，ラットの脳血管の神経について，組織化学ならびに電子顕微鏡による多くの研究があり^{5,6,12,15,18,19,21,29）}，ヒト，イヌ，ハムスター，モルモット，マウスの脳血管についても研究が行われている^2,6,23,24）。最近はヘビやウミガメおよびウシガエルの脳血管にも哺乳動物と同様に神経が存在することが明らかにされている^10,11,25）これらの形態学的研究により，脳血管には交感神経，副交感神経および知覚神経が分布していることが明らかにされているが，Owmanら^20）によれば，免疫組織化学および電顕による研究によりvasoactive intestinal polype—ptide （VIP）を含んだ神神1経線維も脳血管に存在するにとが注目されてきている．

　われわれは以前から雑種成犬を用いて脳循環や脳血管攣縮の実験的研究を行つてきたが，その裏付けとなる犬の脳血管の神経支配に関する報告は，Borodulya＆Ple—tchkovaが組織化学的に内頸動脈を検索したもの^2），佐藤らが電顕的に交感神経支配について研究した報告^24）などがみられるのみであり，特に副交感神経支配に関する研究が乏しいことを知つた。そこで，われわれは犬の脳血管の神経支配を形態学的に確める目的で，雑種成犬の脳血管について組織化学部学的方法により，主としてcholi—nergic nerveの分布および密度を検討し，adrenergicnerveについても検討した。cholinergic nerveに関してはその起源について，未だに文献上明確にされていない点が多く，われわれはその起源について検索を行い，若干の考察を加えた。

The histochemical characteristics of the nerves innervating the cerebral blood vessels were studied in 40 mongrel dogs. Two establised histochemical methods for the demonstration of acetylcholine-sterase and noradrenaline were used to study the distribution of the cholinergic and the adrenergic nerves.

The major arteries of the brain were supplied by extensive networks of the cholinergic and the adrenergic nerves. As the major arteries at the base of the brain passed distally, a diminution in the amount of nerve fibers became evident, and the pial arterioles were only sparsely innervated. The major arteries of the intradural carotid system had a denser innervation of the cholinergic and the adrenergic nerves than the basilar artery.

Along the major arteries, two plexuses (superficial and deep) of the cholinergic nerves were disclosed.The thick nerve bundles of the cholinergic nerves ran longitudinally in the superficial layers of the adventitia and gave off thinner bundles of nerve fibers forming fine networks in the deep layers of the adventitia. Thick nerve bundles consisted of non-myelinated nerve fibers mainly and a few myelinated fibers. No cholinergic nerve could be observed in the media. In contrast with the cholinergic nerves, the adrenergic nerves had many varicoses in the nerve fibers and no thick nerve bundles.

Along the internal ophthalmic arteries which were the most proximal branch of the anterior cerebral artery, the thickest nerve bundles with the highest acetylcholinesterase activity were symmetrically observed. This thickest nerve bundle consisted of nonmyelinated nerve fibers mainly and a few myelinated fibers and branched off at the bifurcation of the internal carotid artery. Thisnerve bundle had negative fluorescence by the method of glyoxylic acid. We detected the con-nection between this nerve bundle and the post-ganglionic nervous network of the ciliary ganglion, and suggested that this nerve bundle was one of the origins of the cholinergic nerves on the cere-bral arteries.

The perforating branches of the anterior cerebral artery and the middle cerebral artery were supplied by dense network of the cholinergic nerves. It was suggested that those might have a close re-lation to autoregulatory function.

We observed the sparse innervation on the cavernous portion and the syphon region of the internal carotid artery, and clarified no cholinergic nerve along the cerebral veins.