Visual and auditory pathways contain cholecystokinin: evidence from immunofluorescence and retrograde tracing

The distribution of cholecystokinin (CCK) in the visual and auditory systems of the rat was studied with combined immunofluorescence and fluorescence retrograde tracing techniques. Double-labeled projection neurons in the pathway from the dorsal lateral geniculate nucleus to area 17 of visual cortex, and from the superior olive to the inferior colliculus demonstrated the presence of CCK-containing pathways in the ascending visual and auditory systems. Thus, CCK can be viewed as a neurotransmitter/neuromodulator candidate in ascending sensory systems.