during the course of experiments designed to study synaptic relationships between the terminals of retinal axons and the various cell populations in the optic tectum of the frog , rana pipiens , we found that neurons in many of the retinorecipient nuclei , including the tectum , are labeled transneuronally following injections of horseradish peroxidase into the optic nerve .
C0228405
optic tectum
C0039433
tectum