Steroid hormones modulate light induced retinal degeneration: protective role of progesterone.

EM. LÓPEZ, LK. JULIÁN, H. COIRINI AND JJ LÓPEZ-COSTA.

San Diego, Callifornia, USA

Congreso; 34th Annual Meeting of the Society for Neuroscience; 2004

Society for Neuroscience

Continuous illumination induces the degeneration of photoreceptors. Our previous results have shown that adrenalectomy partially prevents retinal degeneration induced by continuous illumination showing that glucocorticoid (GC) may collaborate in retinal damage. The aim of the present work was to confirm previous results through the administration of high doses of corticosterone during continuous light exposure. Besides, progesterone was administered to a second group of animals in order to study if this hormone shows a protective effect of the retina.  Fifteen Sprague Dawley rats were submitted to continuous illumination (12000 lux) during 7 days. Along the illumination, a subgroup of 5 rats was treated daily with corticosterone (CORT) (4 mg/kg; sc), another subgroup of 5 rats was treated with progesterone (PROG) (4mg/kg, sc), and the remaining 5 animals were injected with vehicle (control group, CTL). Rats were anesthetized and sacrificed after the illumination period. Eyes were removed and fixed in 4% paraformaldehyde solution. Cryostat sections were stained with hematoxiline-eosine and retinal thickness was determined with a Kontron-Vidas image analyzer. Data were statistically analyzed using the Student Newman-Keuls Multiple comparison test.  After 7 days of illumination, retinal thickness of CORT rats was significantly thinner than that observed in CTL rats (62,29 ± 7,32 ìm vs 69,50 ± 4,89 ìm; p<0,001). On the opposite, retinal thickness of PROG rats was significantly thicker than CTL rats (77,30 ± 8,08 ìm vs 69,50 ± 4,89 ìm; p <0,001). The present results support the hypothesis that GC hormones play an additional deleterious action on retinal damage. In addition, a protective effect of progesterone on light induced retinal damage was observed. (Supported with grants from UBA and CONICET- PIP 819/98).