Immunohistochemical localization of CB1 receptor in canine salivary glands

CB1 is a member of the G-protein-linked receptor superfamily that is present in the central nervous system as well as in certain peripheral neuronal and non-neuronal tissues. Recently, the presence of CB1 was found in the ductal system of the major salivary glands of laboratory animals, but no data are available for domestic mammals. Thus, in the present study, we examined the presence and distribution of CB1 in the major salivary glands of dogs using immunohistochemical techniques. CB1 was found in the parotid and mandibular glands of adult dogs; positive immunoreaction was localized to the cells of the striated ducts, with a peculiar localization on or near the apical membrane. This particular localization may be explained by the characteristics of this receptor as membrane-associated. The acinar structures were completely negative for CB1. We conclude that CB1 is involved in the control of dog salivary secretion via endogenous substances, likely endocannabinoids. The localization of CB1 highlights that endocannabinoids promote qualitative and/or quantitative changes of the primary saliva in the ductal system.