Mast cells in the gastrointestinal tract have been found in close spatial contact with the regulatory cells of gastrointestinal motility: interstitial cells of Cajal (ICC) and myenteric neurons, suggesting their functional interaction. Because of the regulatory role of mast cells even the slight damage or change in activity of these cells may cause considerable disorder of the gut motility. The catechol isoquinoline derivatives are endogenous compounds present in the mammalian brain and the representative one is referred to as salsolinol. Increased salsolinol levels are detected in the cerebrospinal fluid of Parkinson's disease patients. Gastrointestinal dysmotility in those patients has been associated with peripheral action of salsolinol. The aim of this study was to evaluate effects of exogenous salsolinol on mast cells in the gastrointestinal tract of rats. Male Wistar rats (n = 8) were injected intraperitoneally with salsolinol (50 mg/kg/day) for 3 weeks and the equal group served as a control. On the last day the animals were sacrificed, stomachs, small and large intestines were removed, and paraffin embedded specimens were prepared. Slides were toluidine blue stained and the total number and percentage of degranulated mast cells in gastric antral, duodenal and ascending colon wall were assessed by image analysis. The number of mast cells in the gastrointestinal wall was decreased in the salsolinol group compared to the control--in the stomach 98.7 +/- 53.3 vs. 156.7 +/- 45.8, in the duodenum 2.6 +/- 2.1 vs. 7.83 +/- 7.8 and in colon 12.8 +/- 14 vs. 10.7 +/- 17.1 (salsolinol treated vs. control group). Carried out examinations showed the destructive action of salsolinol on the mast cells in all segments examined of gastrointestinal tract.