Relationship between corticoterone doses and light induced retinal degeneration.

E.M. L¨®PEZ, L.K. JULIAN, H. COIRINI AND JJ. LOPEZ-COSTA; JJ. LÓPEZ

Washington, USA

Congreso; 35th Annual Meetinf of the Society for Neuroscience; 2005

Society for Neuroscience

Relationship between corticosterone doses and light induced retinal degeneration EM. L¨®pez1, LK. Juli¨¢n1,2,  H Coirini3 and JJ L¨®pez-Costa1* 1 IBCyN ¡§Prof. E. De Robertis¡§; 2 Servicio de Oftalmolog¨ªa, Hospital de Cl¨ªnicas, UBA; 3 IBYME, 3 Dept Bioqu¨ªmica Humana, Facultad de Medicina, UBA-CONICET, Buenos Aires, Argentina. Continuous illumination induces retinal degeneration (RD) and increases glucocorticoid (GC) levels which collaborate in RD. Previous results from our laboratory have shown that adrenalectomy delayed RD induced by continuous illumination. On the other hand high doses of corticosterone (CORT) administered along continuous light exposure increases RD. The aim of the present work was to evaluate the relationship between different doses of CORT and its deleterious effect on the retina of adrenalectomized rats. Adult male Sprague Dawley rats were adrenalectomized (ADX) and submitted to continuous illumination (12000 lux) during 5 days. Along the illumination, animals were daily subcutaneously injected with either a high dose of CORT (HD-CORT= 4 mg/kg), a low dose of CORT (LD-CORT= 0.4 mg/kg), or vehicle (ADX-CTL). Rats were sacrificed under anesthesia; eyes were removed fixed with 4% paraformaldehyde solution and embedded in paraplast. Sections were stained with hematoxylin-eosin and retinal thickness was determined using a Kontron-Vidas image analyzer. Data was statistically analyzed using the Student Newman-Keuls Multiple comparison test. After 5 days of illumination, retinal thickness of HD-CORT rats was significantly thinner than that observed in ADX-CTL rats (167.3 ¡À 9.46 ¦Ìm vs 193.21¡À9.06 ¦Ìm p<0.001). In addition retinal thickness of HD-CORT rats was significantly thinner than that observed in LD-CORT rats (167.3 ¡À 9.46 ¦Ìm vs 192.06 ¡À 8.83 ¦Ìm; p <0.001). However, retinal thickness of LD-CORT rats was not significantly different from retinal thickness of ADX-CTL rats (p > 0.05). In summary, high doses of CORT contribute to RD while low doses seem to be innocuous. In addition, the present results support the idea that a stressful situation may contribute to the deleterious effect of continuous illumination because the effect of this steroid depends on its circulating levels. (Supported by UBACYT-M20)