PE-11, a peptide derived from chromogranin B, in the rat eye

The aim of the study was to investigate the presence and distribution of PE-11, a peptide derived from chromogranin B, in the rat eye. For this purpose, newborn rats were injected with a single dosage of 50 mg/kg capsaicin subcutaneously under the neck fold and after three months, particular eye tissues were dissected and the concentration of PE-11-like immunoreactivity was determined by radioimmunoassay. Furthermore, PE-11-like immunoreactivities were characterized in an extract of the rat eye by reversed phase HPLC. Then, the distribution pattern of PE-11 was investigated in the rat eye and rat trigeminal ganglion by immunofluorescence. As a result, PE-11 was present in each tissue of the rat eye and capsaicin pretreatment led to a 88.05% (±7.07) and a 64.26% (±14.17) decrease of the levels of PE-11 in the cornea and choroid/sclera, respectively, and to a complete loss in the iris/ciliary body complex. Approximately 70% of immunoreactivities detected by the PE-11 antiserum have been found to represent authentic PE-11. Sparse nerve fibers were visualized in the corneal and uveal stroma, surrounding blood vessels at the limbus, ciliary body and choroid and in association with the dilator and sphincter muscle. Furthermore, immunoreactivity was present in the corneal endothelium. In the retina and optic nerve, glia was labeled. In the rat trigeminal ganglion, PE-11-immunoreactivity was visualized in small and medium sized ganglion cells with a diameter of up to 30 μm. In conclusion, there is unequivocal evidence that PE-11 is a constituent of capsaicin-sensitive sensory neurons innervating the rat eye and the distribution pattern is typically peptidergic in the peripheral innervation but in the retina completely atypical for neuropeptides and unique.