FLUID AND PROTEIN SECRETION BY THE SUBMANDIBULAR GLANDS OF WEANLING RATS IN RESPONSE TO VARIOUS AGONISTS

Secretion of fluid and protein by the submandibular glands of 25-day-old rats was investigated by stimulation with 22 sialogogues classified into five categories, four cholinergic, five beta(1)-, seven alpha(1)- and three alpha(2)-adrenergic, and three peptidergic, at optimal doses. For fluid secretion, cholinergic and peptidergic agonists were the most powerful, whereas the beta(1)- and alpha(1)-adrenoceptor agonists were the most effective for the concentration of protein among the five categories, except for methoxamine. For total output of protein, the beta(1)-, and alpha(1)-adrenoceptor agonists and pilocarpine were the most powerful among the 22 agonists, except for methoxamine and norephedrine. Cholinergic, peptidergic and alpha(2)-adrenergic agonists among the five categories were less effective for protein secretion, except for pilocarpine. For the specific activity of esteroprotease, methoxamine and oxymetazoline, as alpha-adrenoceptor agonists, were the most powerful among the 22 agonists. Thus fluid and protein secretion evoked from the submandibular glands of weanling rats in response to a wide variety of agonists are similar to those of adult rats.