Innervation of the lacrimal gland in the cynomolgous monkey: a retrograde tracing study

Retrograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was used to study the localisation of neurons that innervate the lacrimal gland of the cynomolgous monkey. WGA-HRP-labelled neurons were localised in the ipsilateral trigeminal, superior cervical and ciliary ganglia and in the ipsilateral and contralateral pterygopalatine ganglia. In the trigeminal ganglion WGA-HRP-labelled somata were found in the ophthalmic part (18%) and the maxillary part (5%). Identification of labelled neurons in the ciliary and pterygopalatine ganglia indicates a dual parasympathetic innvervation of the lacrimal gland. There is no known pathway to account for the contralateral location or pterygopalatine neurons. These novel findings are incorporated in a concept of a neural control mechanism for the lacrimal gland.