Doxorubicin-induced behavioral disturbances in rats: protective effect of melatonin and captopril.

OBJECTIVE: Doxorubicin is a recognized chemotherapeutic agent widely employed in human malignancies. The limiting factor of its use is a number of side effects. The aim of this work was to show, whether administration of doxorubicin could induce behavioral disturbances in rats, and whether angiotensin-converting enzyme inhibitor captopril or melatonin can modify these potential alterations. DESIGN AND METHODS: Four groups of 3-month-old Wistar rats (twelve per group) were treated for 4 weeks: control (placebo-treated), doxorubicin (DOX) (5mg/kg i.v. in a single intravenous dose), DOX rats treated with either melatonin (10mg/kg/24h) or captopril (100mg/kg/24h). Systolic blood pressure (SBP) and the level of oxidative stress were investigated and behavioral tests of anxiety-open field test (OF), elevated plus maze (EPM) and light-dark box (LDB) were accomplished. RESULTS: Doxorubicin increased significantly systolic blood pressure and parameters of oxidative stress. Moreover, doxorubicin enhanced the level of anxiety in the tests of OF, EPM, and LDB. Captopril and melatonin prevented the blood pressure rise and the enhancement of oxidative load. Importantly, both substances reduced the parameters of anxiety. CONCLUSION: Chronic administration of captopril or melatonin has shown anxiolytic effect in the model of doxorubicin-induced anxiety. It does not seem unreasonable to suppose that this protective effect of captopril or melatonin against anxiety development might have been related to the antioxidative effects of both substances.

Effect of captopril and melatonin on fibrotic rebuilding of the aorta in 24 hour light-induced hypertension.

Chronic continuous light exposure leads to melatonin deficiency along with complex neurohumoral activation resulting in hypertension development in rats. The aim of this study was to show, whether continuous light induces fibrotic rebuilding of the aorta and whether the treatment with melatonin or angiotensin converting enzyme inhibitor captopril can prevent these potential alterations. In a six-week experiment, 3-month-old Wistar rats were divided into 4 groups (ten per group): controls, rats exposed to continuous light, exposed to continuous light plus treated with captopril (100 mg/kg/24 h) and exposed to continuous light plus treated with melatonin (10 mg/kg/24 h). Systolic blood pressure (SBP) and collagen type I and III in the media of thoracic aorta were measured. Continuous light induced hypertension and fibrotic rebuilding of the aorta in terms of enhancement of collagen I and III concentration in the aortic media. Both captopril and melatonin prevented SBP rise and reduced collagen III concentration in the aorta. However, only melatonin reduced collagen I and the sum of collagen I and III in the aortic tissue. We conclude that in continuous light-induced hypertension, administration of melatonin, along with SBP reduction, decreases collagen I and III concentration in the aorta. It is suggested that antifibrotic effect of melatonin may reduce the stiffness of the aorta and small arteries and beneficially influence the nature of the pulse wave and peripheral vascular resistance.