The vascular architecture and innervation of the cerebral arteries in Leiothrix lutea

The vascular architecture and innervation of the cerebral arteries in the robin-billed leiothrix, Leiothrix lutea, were studied using catecholamine fluorescence, acetylcholinesterase active staining, and immunohistochemical techniques. The cerebral arteries in Leiothrix lutea consisted of the cerebral carotid and the basilar systems. The cerebral carotid artery can be divided into the anterior and posterior rami. Due to poor development of the posterior ramus, the posterior cerebral artery originated from the anterior ramus, and an anterior communicating artery between the cerebroethmoidal arteries formed the circle of Willis. The cerebral carotid system was supplied with aminergic nerve fibers (Amn), cholinergic nerve fibers (Chn) and peptides [substance P (SP), neurokinin A (NKA), calcitonin gene related peptide (CGRP) and vasoactive intestinal polypeptide (VIP)]-like immunoreactive (LI) nerve fibers in all regions. These nerve fibers were abundant in the cerebral carotid system, but were few and scattered in the basilar system. Only neuropeptide Y (NPY)-LI nerve fibers were recognized in moderate numbers in the cerebral carotid system, but were not found in the basilar system. Innervation of the small blood vessels of the cerebral parenchyma differed from that of the cerebral superficial arteries, SP-, NKA-, CGRP- and VIP-LI nerve fibers showed a dense distribution, but Amn and NPY-LI nerve fibers showed a sparse distribution, and almost no Chn was observed. Double staining in the cerebral arteries for SP-, NKA- and CGRP-LI nerve fibers demonstrated exactly the same distribution. This suggests that SP, NKA and CGRP co-exist in the same fiber.(ABSTRACT TRUNCATED AT 250 WORDS)