Different effects of melatonin on experimental granulomatous inflammation.

Several experiments have detected that melatonin exerts a marked influence on the inflammatory process. In the present study we evaluated the effect of exogenous melatonin on the experimental granulomatous tissues in rat. Our data show that subcutaneous administration of different doses of melatonin given daily during 6 days at 9:00 h do not have significant action on the granuloma weight. On the other hand melatonin (4 mg/kg) administered at 17:00 h showed a remarkable action pro-inflammatory. However, this effect was abolished when the animals received previously higher doses of melatonin (40 mg/kg) at 9:00 h.