Characterization of Cannabinoid Receptors in the Peripheral Nervous System and in the Gastrointestinal Tract of Mammals of Veterinary Interest

Cannabis has always been used to treat gastrointestinal (GI) symptoms and pain. By considering the beneficial effects obtained in human medicine, the research in veterinary medicine has focused on the endocannabinoid system (ECS), developing products to treat inflammatory conditions and nociception. The target of these products are cannabinoid receptors (CBRs), with the two canonical cannabinoid receptor 1 (CB1R) and 2 (CB2R), and different putative cannabinoid receptors, such as G protein coupled receptor 3 (GPR3) and 55 (GPR55), peroxisome proliferator-activated receptors α (PPARα) and γ (PPARγ), transient receptor potential vanniloid (TRPV1) and ankirin (TRPA1), or serotonin receptor (5-HT1a, 5-HT2a or 5-HT3a). The principal aim of this research was to evaluate the role of CBRs in the GI tract and in the dorsal root ganglia (DRGs) of different species. The first chapter focuses on the ECS and its components. The second chapter focuses on the GI tract, describing its structure, the interaction with the ECS and the principal pathologies affecting the species of interest, in which the ECS could be involved. The third chapter focuses on DRGs, describing the structure, the role in neuroinflammation and the interaction with the ECS. The experimental studies are divided in: experimental studies about the GI tract; experimental studies about the DRGs; other experimental studies (focus: endoscopy). The localization of CBRs has been investigated in the GI tract of dog, cat and horse and in canine and equine DRGs. The receptors showed similarities and differences in their distribution, underlining how the ECS modulates its expression adapting to physiological (and pathological) conditions between the different species. This research could provide an anatomical substrate upon which it would be possible to develop preclinical and clinical studies aimed to investigate and possibly support the therapeutic use of non-psychotropic cannabinoid in veterinary medicine.