Parasympathetic innervation of the meibomian glands in rats

PURPOSE. To determine the location of parasympathetic neurons that innervat e the meibomian glands in rats. METHODS. The B subunit of cholera toxin (CTB), fast blue, and a retrograde transneuronal tracer, the Bartha strain of pseudorabies virus (PRV-Ba), wer e injected into the tipper eyelids of adult Sprague-Dawley rats after secti oning the ipsilateral branches of the facial nerve and resecting the superi or cervical ganglia. Brains and orbital tissues were processed for the immu nohistochemical detection of PRV-Ba and CTB. In selected cases, series of b rain sections were double labeled for PRV-Ba and tyrosine hydroxylase to de termine the relationship between the A5 noradrenergic cell group and superi or salivatory nucleus, or for PRV-Ba and choline acetyltransferase to estab lish the neurochemical phenotype of parasympathetic preganglionic neurons. RESULTS. Labeled ganglionic cells were diffusely distributed within the ips ilateral pterygopalatine ganglion (PPG) and along the more proximal portion s of the greater petrosal nerve (GPN). Labeled preganglionic neurons were c holinergic and were located immediately dorsolateral to the rostral-most po rtion of the facial nucleus and caudal superior olive, where they interming led with A5 noradrenergic cells. CONCLUSIONS. The meibomian glands and other structures within the lid margi n are subject to parasympathetic regulation by ganglion cells diffusely dis tributed within the PPG and along more proximal portions of the GPN. Cholin ergic parasympathetic preganglionic neurons that project to meibomian gland -innervating ganglion cells are located immediately lateral, dorsal, and ro stral to the facial motor nucleus in the region commonly referred to as the superior salivatory nucleus.