Demonstration of centrifugal fibers in the optic chiasma and optic nerves in the rat after lesions of the suprachiasmatic nucleus

After an unilateral destruction of the suprachiasmatic nucleus and with the use of several silver impregnation techniques, degenerating centrifugal fibers were found in both optic nerves. Centrifugal fibers to the retina originate from three different regions of the nucleus and their position in the chiasma are different. In large majority the degenerating fibers were located at the periphery of the optic nerve and were more frequent on the contralateral than on the ipsilateral side to the destroyed suprachiasmatic nucleus. The possibility that our experimental procedure demonstrates the existence of fibers originating not only in the suprachiasmatic nucleus but also in other structures whose efferent fibers pass at this level, is discussed.