Influence of cannabinoid receptor GPR55 upon salivation of rat submandibular salivary gland

This paper is devoted to elucidation of functionally active cannabinoid receptor GPR55 in submandibular salivary gland cells of rats by introducing a specific agonist lysophosphatidylinositol. We studied the effect of GPR55 activation on the following parameters of basal salivation in vivo: rate of salivation of protein concentration and electrolytes. It was shown that in vivo activation of cannabinoid receptor GPR55 in the acinar cells of submandibular salivary gland by lysophosphatidylinositol caused a dose-dependent reduction in basal flow of saliva. We also elucidated that activation of the cannabinoid receptor GPR55 induced an increase of concentration of total protein in saliva secreted in vivo. That indicate that the activation of cannabinoid receptor GPR55 leads to an enhancement of exocytosis of secretory vesicles in acinar cells. We showed that under conditions of activation of cannabinoid receptor GPR55, changes also occured in concentration of electrolytes in basal saliva such as: reduction in concentration of calcium (Ca2+), inorganic phosphorus (Pi), and increasing concentration of potassium (K+). Based on these findings, we suggest that activation of cannabinoid receptor GPR55 leads to modulation of intracellular signaling mechanisms involved in the secretion of water and electrolytes in acinar cells of rat submandibular salivary gland.