Zoological Studies

A Comparative Study of Neuropeptide Y-Immunoreactivity in the Retina of Dolphin and Several Other Mammalian Species

Shur-Tzu Chen, Ching-Liang Shen, Jiang-Ping Wang and Lien-Siang Chou (1999) The immunoreactivity of an antibody to neuropeptide Y (NPY) in the retina of striped (Stenella coeruleoalba) and Fraser (Lagenodelphis hosei) dolphins and several other species was studied and compared. In dolphin retina, moderate to intense immunostaining was observed primarily in the giant retinal ganglion cells and their dendrite-like processes, while ganglion cells with smaller somata were only weakly immunoreactive. In contrast, NPY immunoreactive cell bodies are mainly located in cells with small somata in the ganglion cell layer and cells resembling amacrine cells in the inner nuclear layer in rat retina. Positive immunostaining was also observed in the inner and outer plexiform layers of rat retina, a feature that was not found in dolphin retina. Interestingly, the overall pattern of NPY expression in the retina of dolphin is similar to that in dog but not in rat, or other mammalian species described previously. One possible explanation is that dolphin and dog are more active by day as compared with rat and cat which are considered to be nocturnal. The variable pattern of distribution of NPY observed in different species suggests that NPY plays a unique functional role, for instance, in the demand for higher levels of blood supply for visual connections through the influence of NPY, in the retinal system in a species-dependent manner probably related to animals’ visual behaviors and environments.