Neuronal nitric oxide synthase and the autonomic innervation of the mouse lacrimal gland

PURPOSE. To determine the expression patterns of the vesicular acetylcholin e transporter (VAChT), tyrosine hydroxylase (TH) and neuronal nitric oxide synthase (nNOS) in the pterygopalatine ganglion (PPG) and the exorbital lac rimal gland of normal mice. METHODS. Mouse PPG and lacrimal glands were processed for single- and doubl e-labeled indirect immunofluorescence studies. Slides were examined with co nventional fluorescence microscopy and confocal laser scanning microscopy. RESULTS. All the somata in the PPG expressed both VAChT and nNOS immunoreac tivity (IR). The postganglionic axons within the ganglion showed less VAChT -immunoreactive intensity than that seen in the somata, whereas nNOS IR was almost undetectable. In the lacrimal gland, nNOS-positive nerve bundles an d fibers were observed to be associated with tear-collecting ducts, blood v essels, and acini. Some nNOS-positive punctate elements appeared to be dist ributed among acini. Many nerve fibers were VAChT immunoreactive and a smal l number of fibers were TH immunoreactive in the gland. Most of the VAChT-p ositive fibers and some of the TH-positive nerves displayed nNOS IR. CONCLUSIONS. The expression of nNOS in cells of the PPG and in lacrimal gla nd nerves suggests that NO may play a role in modulating tear production, T he site of action may include the PPG, ducts, blood vessels. acini, nerve f ibers, and myoepithelial cells within the gland, NO may modulate parasympat hetic and/or sympathetic synaptic transmission or by acting directly on lac rimal gland components. The interaction between NO-ergic and the convention al autonomic input illustrates the complexity of the innervation pattern of the mouse lacrimal gland.