Adrenergic innervation of the cerebral blood vessels in the rabbit

Abstract

✓ The Hillarp technique of fluorescent staining of monoamines was used to examine the adrenergic fibers in the cerebral vessels of rabbit brains. These fibers were found to lie wholly within the deeper layers of the adventitia and not within muscle layers. Varicosities were interpreted as representing neural transmitter substance. The basilar artery had a sparse innervation; the anterior cerebral, carotid, and middle cerebral arteries were more richly supplied by adrenergic terminals, with the most dense innervation in the superficial vessels between 100 and 300 µ in diameter. Mild trauma to the basilar artery, as well as subarachnoid blood without trauma, caused the catecholamine reaction to disappear. A marked depletion of adrenergic fibers was also noted after administration of alpha methyl tyrosine and subjection of the animals to extremes of blood pressure.