Intraocular projections from the pterygopalatine ganglion in the cat

Abstract

The intraocular projection of the cat pterygopalatine (sphenopalatine) ganglion was examined by using retrograde axoplasmic transport techniques in order to investigate the possibility of the involvement of the facial nerve in ocular parasympathetic innervation. Following an injection of horseradish peroxidase (HRP) or wheat germ agglutinin-HRP into the eye, retrogradely labeled cells were observed in the ipsilateral pterygopalatine ganglion, principally in the caudal part. By dissection of silver-impregnated, acetylcholinesterase- and cholinesterase-stained orbital preparations, it was determined that two different nerve pathways link the pterygopalatine ganglion and the eye. One took a retrograde course to join the retro-orbital plexus and then traveled forward accompanying the ciliary artery, the long ciliary nerve, the short ciliary nerve, and/or the optic nerve sheath. The other entered the orbit directly, fused with the ethmoidal nerve or the infratrochlear nerve in a retrograde fashion, and then turned forward along the long ciliary nerve to enter the eye. All these nerves arose from the caudal part of the ganglion. These results are discussed in relation to recent biochemical and histochemical data demonstrating the involvement of the facial nerve in the control of ocular blood flow and intraocular pressure.