NPY and TH innervation in human choroidal whole-mounts

Abstract

To determine the distribution of NPY and TH human choroidal innervation, choroidal whole-mounts were processed for indirect immunofluorescence. An antibody to a component of the neuronal cytoskeleton, neurofilament 200 kDa (NF-200) was used to identify neurons and axons. A double immunostaining was performed, antibodies against NF-200 being combined with antibodies against neuropeptide Y (NPY) and tyroxine hydroxylase (TH). Fibers containing both NPY and TH were distributed in three plexuses, one in the suprachoroid large-sized vessel layer, and two in the medium-sized vessel layer. Intrinsic choroidal neurons (ICNs) containing NPY and TH were observed in the suprachoroid. The TH(+) ICNs were located in the medium-sized vessel layer. Overall, NPY(+) and TH(+) ICNs were more frequent in the central temporal area, both in isolation and forming microganglia. We also detected small spindle elements intensely immunoreactive to TH(+) and distributed mainly in the suprachoroid from the equator to the periphery. In conclusion, the human choroid contains abundant NPY and TH nerve fibers related to chroroidal vascular structures; it further possesses NPY(+) and TH(+) ICNs which contribute to the choroidal self-regulation persisting after sympathetic denervation. Additionally, these ICNs may at least partially explain why the choroidal blood flow does not respond to the factors that influence systemic vascular control. The preferential location of these cells in the submacular area suggests that dysfunction or degeneration of these cells may be a factor in vascular pathologies found in ocular disease, such as diabetic macular edema or age-related macular degeneration.