Salivary gland morphology after alpha-adrenergic and cholinergic stimulation. An ultrastructural study.

The submandibular glands in 100 rats were subjected to different sialagogues: carbachol, clonidine, noradrenalin, and cyclocytidine. The morphological effects of these drugs were compared ultrastructurally. Clonidine, which is an alpha-2-agonist affected mostly the mucous cells, with formation of cytoplasmic vacuoles between the mucous droplets. Noradrenalin and cyclocytidine, both alpha-1-agonists, showed depletion of secretory granules in the serous cells. Noradrenalin also induced cytoplasmic disorganization with enlarged mitochondria, irregular endoplasmic reticulum, and shrinking of the secretory lumen. Carbachol, a cholinergic agonist, was found to produce widespread vacuolization in the cytoplasm of both serous and mucous cells. Small vesicles appeared and mitochondria were destroyed. To induce experimentally a complete depletion of granular serous cells, without other changes in ultrastructural morphology, cyclocytidine was found to be the most efficient drug.