Role of sensory nerves in gastroprotective effect of anandamide in rats.

Previous studies have shown that stimulation of cannabinoid 1 (CB1) receptor protects the gastric mucosa against stress-induced lesion. Aim of the present study was to examine the influence of anandamide on lipid peroxidation and antioxidant defense system in gastric mucosa and the role of sensory nerves in gastroprotective effects of cannabinoids. Studies were performed on rats with intact or ablated sensory nerves (by neurotoxic doses of capsaicin). Gastric lesions were induced by water immersion and restrain stress (WRS). Anandamide was administered at the dose of 0.3, 1.5 or 3.0 μmol/kg, 30 min before exposure to WRS. CB1 receptor antagonist, AM251 (4.0 μmol/kg) was administered 40 min before WRS. WRS induced gastric lesions associated with the decrease in gastric blood flow, mucosal DNA synthesis and mucosal activity of superoxide dismutase (SOD). Serum level of interleukin-1β (IL-1β) and mucosal level of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) were increased. Administration of anandamide reduced the ulcers area, generation of MDA+4-HNE and serum level of IL-1β, and this effect was associated with the reduction in the WRS-induced decrease in gastric mucosal blood flow, mucosal DNA synthesis and SOD activity. Ablation of sensory nerves increased the area of ulcers, serum level of IL-1β and mucosal content of MDA+4-HNE, whereas mucosal DNA synthesis, SOD activity and blood flow were additionally decreased. In rats with ablation of sensory nerves, administration of anandamide at the high doses (1.5 and 3.0 μmol/kg) partly reduced deleterious effect of WRS on gastric mucosa, but this effect was weaker than in animals with intact sensory nerves. Low dose of anandamide (0.3 μmol/kg) was ineffective in the protection of gastric mucosa against the WRS-induced lesions in rats with ablation of sensory nerves. In rats with intact sensory nerves and exposed to WRS, administration of AM251 exhibited deleterious effect. In rats with ablation of sensory nerves and exposed to WRS, AM251 failed to affect mucosal injury in the stomach. We conclude that anandamide reduces the mucosal oxidative stress and exhibits gastroprotective effect against WRS-induced ulcers. These effects are partly mediated by sensory nerves.