Changes in the noradrenaline and acetylcholine content of three major salivary glands and in the salivation and protein component patterns of whole saliva in chronically isoprenaline-administered mice.

One group of mice was injected subcutaneously with 20 mg/kg body wt isoprenaline each day for 10 days; another group (control) was injected with saline. Half the animals of each group were kept untreated for a further 10 days for restoration. Chronic administration of isoprenaline caused enlargement of parotid (4-fold) and submandibular glands (1.7-fold) but had no effect on sublingual glands. Concomitantly, noradrenaline and acetylcholine contents were, in parallel, increased in parotid, decreased in sublingual, and unchanged in submandibular glands. Under these conditions, pilocarpine- or isoprenaline-induced salivation was not affected but phenylephrine-induced salivation was augmented; the protein component patterns of saliva characteristic of the three sialogogues were also changed. In addition, secretory proteins whose synthesis was induced by isoprenaline were found to be secreted by stimulation with different types of sialogogues. Most changes were reversible. These results indicate that continued beta-adrenoceptor stimulation not only causes broadly altered forms of saliva, probably by involving, in part, alpha-adrenoceptor hypersensitivity, but also changes the activities of both sympathetic and parasympathetic nerves to salivary glands in parallel, though the extent differs among the three glands.