CNTF EXERTS OPPOSITE EFFECTS ON IN-VITRO DEVELOPMENT OF RAT AND CHICKPHOTORECEPTORS

EFFECTS Of ciliary neurotrophic factor (CNTF) on photoreceptor develop ment in dissociated cultures of embryonic chick and newborn rat retina were studied using opsin immunoreactivity to characterize photorecept or differentiation. In the presence of CNTF, the number of photorecept ors was increased by up to 200% in chick cultures, but was reduced by 82-99% in rat cultures. The EC(50) determined for CNTF effects in chic k and rat cultures were 0.06 ng ml(-1) and 0.02 ng ml(-1), respectivel y. By studying the time course of in vitro development we showed that CNTF transiently stimulated the generation of photoreceptors from opsi n-negative precursor cells of chick retina, but completely prevented t he same process in rat cultures. These results suggest that CNTF is in volved in the regulation of photoreceptor development, but that it can have different actions in the two species, at least in vitro.