Nerve-stimulated secretion of calcium by rat submandibular gland

The comparative effects of electrical stimulation of parasympathetic (chorda tympani nerve) and sympathetic innervation to the rat submandibular gland on calcium secretion were examined. The separate roles of alpha- and beta-adrenergic receptors in the regulation of calcium secretion during sympathetic nerve stimulation were also determined. The present study shows that the parasympathetic and sympathetic innervations to rat submandibular gland have very different effects on [Ca] of saliva; the regulatory influence of the sympathetic is more prominent than that of the parasympathetic innervation; [Ca] of submandibular saliva evoked by chorda stimulation was about 25 times less than that of saliva evoked by sympathetic stimulation. However, since total volume of chorda-evoked submandibular saliva was about 20 times greater than that of sympathetically evoked saliva, the total output of calcium following stimulation of either autonomic branch was similar. Glandular depletion of calcium for both kinds of nerve stimulation was also similar. Comparison with previous studies on the rat parotid gland shows that the role of the parasympathetic innervation in regulation of [Ca] of saliva and glandular depletion of calcium differed in the two glands while that of the sympathetic innervation was generally similar for both submandibular and parotid glands. Calcium secretion from rat submandibular gland was decreased during sympathetic nerve stimulation in the presence of propranolol, a beta-adrenergic blocker, while it was greatly increased when the sympathetic nerve was stimulated in the presence of phentolamine, an alpha-adrenergic blocker. Thus, it was concluded that with both glands beta-adrenoceptors play the major role in the regulation of calcium secretion.