Development of nitric oxide synthase-immunoreactive nerves in the cerebral arteries of the rat.

Development of cerebrovascular nitrergic nerves was investigated in the rat, using immunohistochemistry for nitric oxide synthase (NOS) and quantitative analysis. Cerebral perivascular NOS nerves usually appeared on the walls of both the intracranial part of the internal carotid artery (ICA) and the internal ethmoidal arteries (IEA) at birth. NOS nerves via the IEA grew more rapidly than those via the ICA. They extended over all the major arteries located more rostral than the middle part of the basilar arteries during the third postnatal week, while those from the ICA remained limited to the caudal segment of the anterior circulation and to the rostral segment of the posterior circulation throughout development. The appearance of NOS nerves on the vertebrate artery (VA) was not demonstrated before the third postnatal week, being apparently far late in development as compared to that of the same nerve type on the ICA and IEA.