Desynchronosis and erosive and ulcerative lesions of the stomach in rats active or passive in the open-field test: effect of exogenous melatonin.

We studied the effect of a phase shift in circadian rhythms (desynchronosis) on the development of erosive and ulcerative lesions in the gastric mucosa in male Wistar rats with different behavioral activity in the open-field test. The animals kept under conditions of natural or shifted light-dark cycle were untreated or intraperitoneally received physiological saline (1 ml) and melatonin (1 or 2 mg/kg). Desynchronosis induced gastric ulcers in active rats not receiving injections or intraperitoneally injected with physiological saline. No gastric ulcers were found in passive animals kept under shifted light-dark cycle. Melatonin induced gastric ulcers in passive animals kept under natural light-dark cycle. Gastric ulcers were not found in active rats subjected to desynchronosis and receiving melatonin. Our results indicate that treatment with melatonin for the correction of changes induced by shifts in the light-dark cycle should be performed taking into account individual behavioral characteristics.