There has been considerable controversy concerning the motor innervation of cerebral arteries. Bayliss et aL (1) and Hill and MacLeod (2) reported no evidence of any vascular response suggesting the existence of vasomotor nerves supplying the vessels of the brain. Dumke and Schmidt (3) also found
little effect of sympathetic stimulation on cerebral blood flow, as did Carlyle and Grayson (4), who concluded that non-nervous autoregulation is the most important factor in the control of cerebral blood flow. The view of these authors (1-4) and others that vasomotor nerves are of minor importance in the
regulation of cerebral blood flow has been supported in recent reviews (5-7), but these conclusions have been recently challenged by James et al. (8), who implicated vasomotor nerves in the responses of cerebral vessels to changes in blood CO2 levels. Earlier than this, Hiirthle (9) and Forbes and Cobb (10) had observed clear responses of cerebral arteries to motor nerve stimulation. Forbes and Cobb observed a constriction of cerebral arteries in response to sympathetic stimulation and a
dilatation, which was blocked by atropine, in response to parasympathetic stimulation.
Meyer et al (11), using a preparation similar to that of Dumke and Schmidt (3), recently
observed a 22 to 30% reduction in internal carotid blood flow when the cervical sympathetic nerve was stimulated.
This work has clearly shown a dual
adrenergic and nonadrenergic innervation of
the anterior cerebral arteries of the rat. Two
types of nerve fiber can be distinguished by
their vesicle inclusions in tissue fixed in
permanganate or, after treatment with 6-
OHDA, in osmium or glutaraldehyde. The
first type contained many small granular
vesicles and degenerated after cervical sympa-
thectomy. Fluorescent, noradrenaline-contain-
ing fibers were detected around the cerebral
arteries; after sympathectomy, these fibers also
degenerated. This suggests that the axons
containing small granular vesicles are adrener-
gic.
Copyright © 1970 American Heart Association. All rights reserved. Print ISSN: 0009-7330. Online ISSN:
TX 72514
Circulation Research is published by the American Heart Association. 7272 Greenville Avenue, Dallas, 1970;26;635-646
Circ. Res.T. IWAYAMA, J. B. FURNESS and G. BURNSTOCK
From the Department of Zoology, University of
Melbourne, Parkville 3052, Victoria, Australia.
This investigation was supported by grants from the
National Heart Foundation of Australia and the
Australian Research Grants Committee.
Dr. Iwayama's permanent address is Department of
Anatomy, Faculty of Medicine, Kyushu University,
Fukuoka, Japan.
Received January 5, 1970. Accepted for publication
March 9, 1970.
