Cholecystokinin in the cat retina. Action of exogenous CCK8 and localization of cholecystokinin-like immunoreactivity.

The effects of applying cholecystokinin (CCK8) iontophoretically onto cat retinal ganglion cells were studied in the optically intact eye of the cat. CCK8 suppressed both the maintained and the light evoked discharge of brisk ganglion cells, irrespective of their being on- or off-center, brisk-transient, or brisk-sustained and independent of the state of light adaptation. The inhibitory action of CCK8 in the cat retina is opposite from its excitatory action in other parts of the brain. Using an antiserum to cholecystokinin, immunoreactivity was localized in horizontal cells and amacrine cells of the cat retina. Inconsistently immunoreactivity also was found in ganglion cells and fibers.