RESUMEN
OBJECTIVE: To investigate the effects of chronic high dose sumatriptan and dipyrone treatment on central serotonergic system in rats. MATERIALS AND METHODS: Male Sprague-Dawley rats (seven per group) were daily injected with sumatriptan (3 mg/kg), dipyrone (400 mg/kg) or saline for 30 days. The brains of animals were surgically removed and immunohistochemically stained for serotonin. Serotonin-positive stained cells were counted automatically by using a computerized image analysis program. Statistical analysis carried out using one-way ANOVA followed by post hoc Tukey test. RESULTS: A significant decrease in serotonin-positive cells in the brainstem was observed after chronic sumatriptan administration while chronic use of dipyrone induced a significant increase in serotonin-positive cells both in the cortex and midbrain. CONCLUSION: Our data suggest that central serotonergic system might be modified by chronic use of sumatriptan and dipyrone.