Distribution of the inositol trisphosphate receptor in the catfish retina

Inositol 1,4,5-trisphosphate (InsP₃) mobilizes intracellular stored Ca²⁺ by binding to specific receptors that are similar to the ryanodine receptor of skeletal and cardiac muscle. We have immunolocalized the InsP₃ receptor to the inner nuclear layer and limiting membranes of the catfish retina. Immunocytochemistry on dissociated retinal cells further localized the receptor in the horizontal, bipolar and Muller glial cells. Immunostaining of the rat retina localized the InsP₃ receptor to the plexiform layers. These data show a different distribution of InsP₃ receptor in the catfish retina compared to that of other vertebrates, that may be suggestive of a different functional role for this receptor in different species.