The origin of tectal NPY immunopositive fibers in the frog

A dense network of NPY immunopositive fiber terminals was found in the retinal recepient and less in number in the periventricular fiber layers of the optic tectum. Axons of immunostained cells in the pretectal area, and torus semicircularis could be followed to the rectum. Eye removal did not influence tectal NPY immunopositive, while a pretectal lesion markedly reduced this immunoreaction ipsilateral to the lesions. Lesions of the torus semicircularis did not tectal NPY immunopositivity. It is concluded that the main source of NPY immunoreactive fibers is the posterior thalamic nucleus in the pretectal region, while the periventricular NPY immunopositive fibers may be of intrinsic origin.