Acetylcholinesterase-positive and paraformaldehyde-induced-fluorescence-positive innervation in the upper eyelid of the sheep (Ovis aries)

This is the first study which describes the innervation of some eyelid stru ctures, such as the glands of Moll and the glands of Zeiss. It is also the first to investigate the innervation pattern of the eyelid as a whole. We h ave studied the acetylcholinesterase-positive and paraformaldehyde-induced- fluorescence-positive (FIF+) innervation pattern of the different structure s that constitute the upper eyelid of the sheep. There is widespread acetyl cholinesterase-positive innervation in the epithelium, but not such an abun dant FIF+ innervation. Both types of innervation are represented in the con nective tissue by trunks or fibers that are distributed towards the differe nt structures immersed within them. In the glands of Zeiss, cholinesterase- positive innervation is much more widespread than FIF innervation. On the c ontrary, the glands of Moll present denser FIF+ innervation than acetylchol inesterase-positive innervation. The Meibomian glands and the lachrymal gla nds show a rich acetylcholinesterase-positive and FIF+ innervation. Eyelid muscle innervation is mainly acetylcholinesterase-positive. In the conjunct ive membrane there is no acetylcholinesterase-positive innervation, and onl y scarce FIF+ fibers can be demonstrated.