Neurotransmitter contents in the retina of RCS rat

Background: Retinitis pigmentosa is a hereditary disease characterized by g radually developing degeneration of photoreceptors, The Royal College of Su rgeons (RCS) rat is an experimental model of retinitis pigmentosa. However, there is a paucity of information concerning neurotransmitter contents in the retina of RCS rats. Thus, we determined the retinal contents of neurotr ansmitters in RCS rats at 4 and 23 weeks postnatally and in age-matched con genic control rats. Methods: Dopamine (DA) and acetylcholine (ACh) were ele ctrochemically measured by highperformance Liquid chromatography (HPLC). Ne uroactive amino acids, including gamma -aminobutyric acid (GABA) and taurin e, were determined by means of an HPLC-precolumn derivatization method. Res ults: Contents of DA, ACh, glutamate, aspartate and GABA in the retina of R CS rats 4 weeks postnatally were within normal ranges. At 23 weeks, the ret inal contents of DA, glutamate and aspartate in the RCS rats were significa ntly lower than in the age-matched control rats, while the contents of BCh and GABA were unaffected even at this later stage. On the other hand, the r etinal content of glycine in the RCS rats at 23 weeks was significantly hig her than that in the age-matched control rats. It is interesting to note th at the content of taurine in the RCS rats had already decreased at 4 weeks postnatally and the decrease was more marked at 23 weeks. Conclusion: The d ecrease in taurine content is probably the first sign of degeneration revea led by the retinal neurotransmitters of RCS rats.