Possible role of serotonin in Merkel-like basal cells of the taste buds of the frog, Rana nigromaculata.
Merkel-like basal cells in the taste buds of the frog were examined by fluorescence histochemistry, immunohistochemistry and electron microscopy. There were about 16-20 basal cells arranged in a radial fashion at the base of each taste bud. These cells were strongly immunopositive for serotonin antiserum. They were characterised by the presence of numerous dense-cored granules in the cytoplasm ranging from 80 to 120 nm in diameter, and of microvilli protruding from the cell surface. For 4 mo after sensory denervation by cutting the gustatory nerves, all cell types of the taste bud were well preserved and maintained their fine structure. Even at 4 mo after denervation, the basal cells exhibited a strong immunoreaction with serotonin antiserum. To investigate the function of serotonin in the basal cells in taste bud function, serotonin deficiency was induced by administration of p-chlorophenylalanine (PCPA), an inhibitor of tryptophan hydroxylase, and of p-chloroamphetamine (PCA), a depletor of serotonin. After administration of these agents to normal and denervated frogs for 2 wk, a marked decrease, or complete absence, of immunoreactivity for serotonin was observed in the basal cells. Ultrastructurally, degenerative changes were observed in both types of frog; numerous lysosome-like myelin bodies were found in all cell types of the taste buds. The number of dense-cored granules in the basal cells also was greatly decreased by treatment with these drugs. Serotonin in Merkel-like basal cells appears to have a trophic role in maintenance of the morphological integrity of frog taste bud cells.
Department of Oral Anatomy and Neurobiology, Kyushu Dental College, Kitakyushu, Japan.
K
K
Hamasaki
Y
Y
Seta
K
K
Yamada
K
K
Toyoshima
D000818:Animals; D003714:Denervation; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D018862:Merkel Cells / Q000378:metabolism*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D011898:Ranidae / Q000033:anatomy & histology / Q000378:metabolism*; D012701:Serotonin / Q000032:analysis / Q000502:physiology*; D013650:Taste Buds / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D013997:Time Factors
D012701:Serotonin