Innervation of Two Peptidergic (Substance P and Calcitonin gene-related peptide) Nerves in the Cerebral Arteries and Choroid Plexus of the Japanese Newt (Triturus pyrrhogaster)

Abstract

The pattern of cerebrovascular substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactive (-IR) innervation was investigated in the newt. SP-IR nerves supplying the cerebral arterial tree and choroid plexus were positive for CGRP, but negative for vasoactive intestinal polypeptide or neuropeptide Y. It is suggested that cerebrovascular SP- and CGRP-IR axons are sensory in nature. The supply of SP- and CGRP-IR nerves to the major cerebral arteries is relatively poor. Nevertheless, numerous SP- and CGRP-IR axons, which are contained in the fiber bundles on the cerebral carotid artery and the basilar artery, spread widely over the microvascular-epithelial regions of the choroid plexuses. It must be considered in relation to the significant role of SP-and CGRP-IR neuronal mechanisms responsible to the microcirculation, cerebrospinal fluid (CSF) production and transport action within the choroid plexus in the nutrition of the newt brain via the CSF.