Parasympathetic motoneurones in the oculomotor complex which innervate the ciliary ganglion were identified using the horseradish peroxidase (HRP) retrograde axonal tracer technique. The ciliary ganglion was located behind the eye by a lateral orbital approach and injected with HRP pellets mounted on the tips of microelectrodes. Most of the labelled cells were distributed throughout the whole Edinger-Westphal nucleus (EW). Outside the EW, only a small number of labelled cells were found, and most of these were located in the median zone ventral to the EW. There was no evidence of a division of the EW into rostral and posterior subnuclei, nor for separate cell populations in the EW and the anterior median nucleus (AM), respectively. At rostral levels labelled cells were confined to the EW with no overlap into the AM. In contrast to most previous studies no labelled cells were found in the AM. The possible physiological functions of the EW and the ventral components of the EW are discussed.

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