Role of the autonomic nervous system in regulating salivary mucin secretion by the canine submandibular gland in vivo.

The secretion of mucin was assessed by measuring changes in protein and sialic acid concentrations in saliva. Electrical stimulation of the sympathetic nerve increased protein and sialic acid concentrations greatly but stimulation of the parasympathetic nerve by bethanechol (5-20 micrograms/kg, intravenously) caused a slight increase. Sympathomimetic drugs (1-10 micrograms/kg, intravenously) also increased protein and sialic acid concentrations (isoproterenol greater than adrenaline greater than noradrenaline). Mucin secretion was increased by H133/22, a beta 1 adrenoceptor agonist, or terbutaline, which is roughly equipotent. Adrenaline-induced mucin secretion was inhibited by propranolol, but not by tolazoline. These data suggest that mucin secretion is predominantly regulated by the sympathetic nervous system via beta adrenoceptors, both beta 1 and beta 2.