Expression of Substance P in the Experimental Diabetic Rat Retina / 대한해부학회지

ABSTRACT

Substance P (Sub P) being composed of 11 amino acids sequence is a kind of tachykinin family peptides. It has been known that this substance plays a role of neurotransmitter and/or neuromodulator and is a very potent vascular growth factor in the nervous system. This study has been investigated expression pattern of Sub P in the rat retina at normal and alteration of Sub P expression following diabetic injury using immunohistochemistry. Diabetic condition was induced by a single injection of streptozotocin in Sprague-Dawley rats aged 8 weeks. The animals showing high blood glucose levels (above 300 mg/dL) were cared for 1, 4, 8 and 12 weeks, respectively. The whole-mounted or sectional preparations of the retinas were used for Sub P immunohistochemistry. Sub P immunoreactivity has been localized in subsets of amacrine cells in the inner nuclear layer (INL) and displaced amacrine cells in the ganglion cell layer (GCL) in the normal retina. The dendrites from amacrine cells in the INL were ramified with strata 1 and 3, and those from displaced amacrine cells in the GCL with strata 5 of the inner plexiform layer. Sub P immunoreactive neurons in both the INL and the GCL were more densely populated in the superior half of the retina. During diabetes, the cell number of Sub P immunoreactive neurons was decreased to one third of the normal value at 4 weeks of diabetes and then slightly increased to half of the normal value at 12 weeks of diabetes. In addition, Sub P mRNA levels were reduced at 4 weeks but reincreased at 12 weeks. These results suggest that Sub P in the rat retina at normal state may function differentially in the superior or the inferior halves and Sub P synthetic pathway in the retinal neurons maybe irradiated in earlier stages of diabetic retinopathy.