The effect of melatonin treatment on the development of retinal damage induced by continuous high intensity illumination (CHII) was investigated. Melatonin-treated rats developed more severe impairment of retinal structures compared with controls. In a similar study rats treated with bromocriptine, a potent stimulator of dopamine receptors, developed far less damage in their retinas during and after CHII compared with nontreated animals. Bromocriptine also increased the survival of retinas in rats with hereditary retinal degeneration (RCS strain).