Nerve growth factor in the developing and adult lacrimal glands of rat with and without inherited retinitis pigmentosa

Purpose: In the present study, we investigated lacrimal function and presence of the neurotrophin nerve growth factor (NGF) and its receptors in the lacrimal gland (LG) of normal rats and rats with inherited retinitis pigmentosa (IRP). Materials and Methods: After anesthesia, modified Schirmer tests were performed on IRP rats and Sprague Dawley (SD) rats to measure tear function. LGs of developing and adult IRP and SD rats were removed and used for histological, immunohistochemical, and biochemical analyses. Results: The results showed that basal tear secretion is reduced in IRP rats as compared with SD rats. NGF and NGF receptors are expressed in the LG of both rat strains. In SD rats, these NGF markers are low during early life and more elevated in adult life. Conversely in rats with IRP, NGF and its receptors decreased in adult life. Conclusions: The role of NGF in maintaining ocular surface integrity is well known. The observations of this study further support the hypothesis that neurotrophins play a role in modulating tear secretion and probably in preventing the deleterious effects of dry eye. This hypothesis is presented and discussed.