In vivo changes in free choline level induced by autonomic agonists in mouse organs, including three major salivary glands

Whether free choline levels are changeable in vivo in response to different types of autonomic agonists was examined in several mouse organs. Upon one subcutaneous injection of isoproterenol, phenylephrine and pilocarpine, choline levels in whole organ decreased, increased and decreased, respectively, in various organs within 30 min and returned to initial levels in a day. In the three major salivary glands, a delayed choline elevation also appeared on day 2 after one isoproterenol injection and subsided by day 6. Only in the three salivary glands more choline was accumulated after 10 once-a-day injections of isoproterenol than after one isoproterenol injection. Neither phenylephrine nor pilocarpine induced comparable choline accumulation in any organs examined. Isoproterenol injection repeated at a 2-day interval augmented the subsequent, delayed choline elevation. Examination with dobutamine and the adenylyl cyclase activator 6-(3-dimethylaminopropionyl)forskolin suggested that isoproterenol-induced immediate choline lowering was downstream of cAMP synthesis and linked to cAMP more tightly than the choline accumulation, though both choline changes occurred via β₁-adrenergic receptors. Choline levels in the salivary glands also changed depending on the form of diet given and particularly in the parotid gland in parallel with gland weights. These results provide the first evidence for the autonomic control of intracellular choline levels; intracellular choline levels might be an integral part of the autonomic signalling pathway.