TRANSNEURONAL RETINAL INPUT TO THE PRIMATE EDINGER-WESTPHAL NUCLEUS

The Edinger-Westphal nucleus of the oculomotor nuclear complex provide s preganglionic parasympathetic innervation to the pupil. We labelled its retinal input by transneuronal autoradiography after an eye inject ion of [H-3]proline in the macaque monkey. The primary retinal project ion to the pretectum terminated in the ipsilateral and contralateral o livary nuclei. These nuclei were intensely labelled and sharply delimi ted, with a mean diameter of 590 mu m and a rostrocaudal length of 2.5 2 mm. The caudal half of the olivary nucleus on each side broke into m ultiple clumps of label. Fragments of label also surrounded each oliva ry nucleus. The exact pattern of pretectal labelling varied considerab ly among animals and even from side to side in the same animal. In 5 o f 6 monkeys, label from the olivary nucleus reached the Edinger-Westph al nucleus transneuronally. In transverse sections, the Edinger-Westph al label appeared as a circular patch located on either side of the mi dbrain ventral to the cerebral aqueduct in the central gray matter. It averaged 230 mu m in diameter and 610 mu m in length. In Nissl-staine d sections, the autoradiographic label corresponded to a distinct nucl eus comprised of neurons that were smaller than neurons in nearby soma tic subdivisions of the oculomotor complex. The mean area of Edinger-W estphal neurons was 295 mu m(2). Transneuronal retinal input to the Ed inger-Westphal nucleus mediating pupillary constriction terminates in a single, well-defined cell group in the midbrain. (C) 1997 Wiley-Liss , Inc.