has soma location has soma location expresses expresses parasympathetic neuron ciliary ganglion VIP/PHI neuron 2026-03-13T11:13:54Z A parasympathetic postganglionic neuron whose soma is located in the ciliary ganglion and that co-expresses vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI, both encoded by the VIP gene). This neuron provides parasympathetic innervation to the eye, contributing to regulation of pupillary constriction and ciliary muscle accommodation. It has been identified in human ciliary ganglia by immunohistochemistry (Kiyokawa et al. 2012, PMID:22095632). VIP/PHI co-expression distinguishes this subpopulation from other cholinergic parasympathetic neurons in the ciliary ganglion and is characteristic of a subset of cranial parasympathetic neurons in humans and other mammals. ciliary ganglion VIP-PHI neuron VIP peptides main ciliary ganglion