Norepinephrine is a presynaptic input to visual corpus callosum cells.

The neurochemical identity of presynaptic inputs to cell bodies of corpus callosum fibers (callosal cells) located in visual cortex of the cat was investigated using a double labeling technique. Callosal cells were labeled by horseradish peroxidase applied to the severed ends of callosal fibers, and [3H]norepinephrine (NE) was injected into the crown of the lateral gyrus corresponding to the visual cortical area 17/18 border to label synapses. The tissue surrounding the injection sites was processed for electron microscope autoradiography. The results show that NE can be localized to cortical synapses contacting callosal cells in visual cortex of the cat.