Adrenergic innervation of human middle cerebral artery. Ultrastructural observations

The innervation of the human middle cerebral artery is studied with transmission electron microscopy using the chromaffin reaction technique. Adrenergic nerve fibers and related terminals, with granular electrodense neurotransmitter vesicles, are confined to the tunica adventitia-tunica media transitional zone and the outer layers of the media. These findings may indicate the presence of an adrenergic vasoconstrictor system for circulation control in the human middle cerebral artery.