| Abstract |
We hypothesize variation in expression and localization, along the course of the glandular tubule, of muscarinic
cholinergic receptor M1which plays as a distinct contribution, though minor in comparison with M3receptor, in
saliva secretion. Localization of the M1 receptor was examined using immunohistochemistry in three major
salivary glands. Although all glandular cells were more or less M1-immunoreactive, acinar cells were weakly
immunoreactive, while ductal cells exhibited substantial M1-immunoreactivity. Many ductal cells exhibited clear
polarity with higher immunoreactivity in their apical/supra-nuclear domain. However, some exhibited indistinct
polarity because of additional higher immunoreactivity in their basal/infra-nuclear domain. A small group of
cells with intense immunoreactivity was found, mostly located in the intercalated ducts or in portions of the
striated ducts close to the intercalated ducts. In immuno-electron microscopy, the immunoreactive materials
were mainly in the cytoplasm including various vesicles and vacuoles. Unexpectedly, distinct immunoreactivity
on apical and basal plasma membranes was infrequent in most ductal cells. The heterogeneous localization of
M1-immunoreactivity along the gland tubular system is discussed in view of possible modulatory roles of the M1
receptor in saliva secretion. |
Publication
Journal Publication
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