Innervation Pattern of Noradrenergic and Acetylcholinesterase-Positive Nerves in the Extracranial Internal Carotid Artery and Cerebral Arterial Tree of the Japanese Quail.

Abstract

The density and distribution of noradrenergic (NA) and acetylcholinesterase-positive (AChE) nerves in the extracranial part of the internal carotid artery (eICA) and cerebral arterial tree of the Japanese quail were investigated using specific histochemical techniques. The eICA and the major cerebral arteries in this bird were richly supplied with a large number of NA nerves, but had a very poor or no supply of ACNE nerves. The cerebral arteries located more caudally than the proximal part of the anterior ramus were generally devoid of ACNE nerves, while the internal ethmoidal artery (IEA) was usually equipped with fiber bundles positive for AChE. The above finding suggests that all or nearly all of cerebral perivascular AChE nerves path through the ethmoidal foramen, and project to the cerebral arterial system via the IEA. This differs from the cerebrovascular NA Innervation in that NA nerves enter the cranial cavity through the IEA, ICA and the vertebral artery, mainly via the ICA. A significant finding is that a few AChE nerve cells are present on the major cerebral arteries of the internal carotid system, mainly the IEA. Thus, the quail cerebral arterial system is dually innervated by the axons from extrinsic and intrinsic AChE neurons in some individuals. The unique NA and AChE innervation in the eICA and cerebral arteries of the quail must be considered in relation to the presence of NA and cholinergic vasomotor mechanisms responsible for the regulation characteristic of cerebral circulation in this bird.