Presence of neuronal nitric oxide synthase in autonomic and sensory ganglion neurons innervating the lacrimal glands of the cat: an immunofluorescentand retrograde tracer double-labeling study

It is generally considered that parasympathetic postganglionic nerve fibers innervating the lacrimal gland (LG) arise from the pterygopalatine ganglio n (PPG), while sympathetic and sensory innervations arise from the superior cervical ganglion (SCG) and trigeminal ganglion (TG), respectively. Recent ly, we reported for the first time that the parasympathetic innervation of the cat LG was also provided by the otic ganglion (OG) and ciliary ganglion (CG), and that the sensory innervation was also provided by the superior v agal ganglion (SVG) and superior glossopharyngeal ganglion (SGG). To determ ine if nitric oxide (NO) is a neurotransmitter of the autonomic and sensory neurons innervating the LG, we injected the cholera toxin B subunit (CTB) as a retrograde tracer into the cat LG, and used double-labeling fluorescen t immunohistochemistry for CTB and nitric oxide synthase (NOS). We found th at NOS-/CTB-immunofluorescent double-labeled perikarya were localized in th e PPG, OG, TG, SVG and SGG, but not in the CG and SCG. The highest numbers of NOS-/CTB-immunofluorescent double-labeled neurons were found in the PPG and TG. In addition, we examined the presence of nitrergic nerve fibers in the LG using NADPH-d histochemistry and found that a large amount of NADPH- d-stained nerve fibers were distributed around the glandular acini and in t he walls of glandular ducts and blood vessels. This study provides the firs t direct evidence showing that NO may act as a neurotransmitter or modulato r involved in the parasympathetic and sensory regulation of lacrimal secret ion and blood circulation, but may not be implicated in the sympathetic con trol of LG activities, and that nitrergic nerve fibers in the LG arise main ly from parasympathetic postganglionic neurons in the PPG and sensory neuro ns in the TG. The present results suggest that NO plays an important role i n the regulation of LG activities. (C) 2001 Elsevier Science B.V. All right s reserved.