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C Ding, B Walcott, KT Keyser; The Regional Differences of Innervation and the Sympathetic Control of Protein Secretion in the Mouse Lacrimal Gland . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3138.
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Purpose: The mammalian lacrimal gland is innervated by both the parasympathetic and sympathetic nerve systems. There is evidence that the sympathetic system plays a direct and important role in tear secretion. The present study was intended to explore the innervation pattern and sympathetic nervous system’s role in protein secretion from the exorbital lacrimal glands of normal mice. Methods: Mouse lacrimal glands were processed for single and double labeled indirect immunofluorescence studies to reveal the parasympathetic and sympathetic innervation patterns. The sections were examined with both conventional fluorescence microscopy and confocal laser scanning microscopy. The sucrose-potassium phosphate-glyoxylic acid method was also used to visualize the adrenergic system. Cholinergic and adrenergic agonists (carbachol, norepinephrine, phenylephrine, and isoproterenol) were applied to isolated gland fragments to explore their effects on protein secretion. Results: The mouse lacrimal gland can be divided into two different areas based on the innervation density and distribution pattern. One area, comprising 10∼30% of the gland, exhibited much higher parasympathetic and sympathetic innervation density than the rest of the gland. Norepinephrine (alpha and beta receptor agonist) and phenylephrine (alpha1 agonist) induced protein secretion similar to that induced by carbachol (a cholinergic agonist), at 10-6, 10-5, and 10-4 M, with the maximal responses achieved at 10-5 M. Isoproterenol, a beta adrenergic agonist, elicited protein secretion at 10-5 and 10-4 M in the present study. Conclusion: Our data indicate that there is much more extensive sympathetic innervation in regions of the mouse lacrimal gland than previously reported. The division of the lacrimal gland into two areas suggests that the mouse lacrimal gland is a mixed gland and these two areas may play different roles in the protein secretory process in different situations. Our data support the notion that the sympathetic system in the mouse lacrimal gland is in direct association with protein secretion and differential secretion is accomplished by activating different populations of lacrimal cells.
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