Abstract
Abstract: :
Purpose: To evaluate whether secretoneurin (SN) represents a sensory neuropeptide innervating the anterior segment of the eye. Methods: The trigeminal ganglia (TG), the ganglia cervicale superius (GCS) and eye tissues were analyzed for the presence of SN by a highly sensitive radioimmunoassay both in capsaicin pretreated and sympathetically denervated rats. The expression of secretogranin II (SgII) mRNA was studied in the rat TG by in situ hybridization and the processing of SgII by gel filtration chromatography. Then, the concentration of the peptide was determined in human eye tissues and nerve fibers were visualized by immunohistochemistry. Results: There were significant amounts of SN present within the TG and capsaicin pretreatment led to a 57.01% (± 4.29) and 59.07% (±11.86) decrease of the concentration in the TG and the iris/ciliary body complex, respectively. Sympathetic denervation by axotomy failed to lower the concentration on SN in particular eye tissues. The SgII probe labeled numerous cells of various size within the TG and the precursor of the peptide was found to become completely processed to SN. In human eyes, the highest levels of the peptide were found in the choroid and nerve fibers could be visualized predominantly in the iris/ciliary body complex and the choroid. Conclusion: There is unequivocal evidence that SN represents a constituent of capsaicin–sensitive sensory neurons innervating the eye and indicates participation of this peptide in sensory transmission.
Keywords: neuropeptides • anterior segment • anatomy