Abstract
Purpose: :
Pericytes are contractile cells surrounding blood vessels. They might be involved in the vessels caliber regulation and therefore in blood flow homeostasis.In this study, we address the question whether pericytes in the choroid receive input from the autonomic nervous system and therefore might be involved in ocular blood flow regulation.
Methods: :
Rat choroidal wholemounts and sections were prepared for immunohistochemistry of the pericyte marker chondroitin sulfate proteoglycan (NG2) and the pan-neuronal marker PGP9.5, or tyrosine hydroxilase (TH), vasoactive intestinal polypeptide (VIP), choline acetyl transferase (ChAT) and calcitonin-gene related peptide (CGRP). Additionally, PGP9.5 and TH were analyzed in the DCX-dsRed transgenic rat choroid, a putative model to study pericytes function in-vivo.
Results: :
In the rat choroid, NG2 immunoreactivity was detected in cells and processes surrounding blood vessels. These NG2 positive cells were not co-localized with PGP9.5, but received close appositions of PGP9.5, TH, VIP and ChAT immunoreactive boutons. Blood vessels were densely surrounded by NG2 positive processes, in close vicinity to TH, VIP, ChAT and CGRP positive fibres and boutons. In the DCX-dsRed transgenic rat, PGP9.5 and TH were screened and revealed dense appositions of the respective markers on the dsRed positive cells, a subpopulation of which is also positive for NG2.
Conclusions: :
Besides the innervations of vascular smooth muscle cells, the close relationship of sympathetic (TH) and parasympathetic (VIP, ChAT) nerve fibres on NG2 positive processes might indicate an additional target of the autonomic nervous system for choroidal blood flow regulation, while the role of primary afferent fibres (CGRP) remains unclear. Although additional experiments are needed, regarding the autonomic innervation, similar findings in the DCX-dsRed transgenic rat indicate this model potentially suitable for in-vivo experiments unveiling the role of pericytes in blood flow regulation.
Keywords: immunohistochemistry • neurotransmitters/neurotransmitter systems • anatomy