RESUMO
BACKGROUND & OBJECTIVES: Several lines of evidence point to a significant role of antioxidants in Parkinson's disease (PD). Few studies report that melatonin, a neurohormone, is one of the best physiological antioxidants. Review of literature indicates that none of the drugs so far studied for preventing the PD was found to be promising for use. Therefore in the present study the effect of neuroprotectory melatonin was tested against 6-hydroxydopamine (6-OHDA) neurotoxicity for striatal dopaminergic neurons in the rat. METHODS: Thirty animals were randomly divided into two groups. Animals of group 1 received saline (melatonin vehicle) daily 1 ml ip for seven days. Melatonin (500 mug/kg body weight dissolved in 1 ml saline ip) was administered in rats of group 2 for seven days. Then all animals of groups 1 and 2 were lesioned unilaterally with 8 mug 6-OHDA into the lateral striatum on 8(th) day. Various behaviour and histological tests were used to evaluate the neuroprotective effect of melatonin. RESULTS: Statistically significant difference in various behaviour tests was found between post lesion values of group 1 and group 2 (P<0.001 in apomorphine-induced rotational behaviour, staircase test (success rate), disengage time and P<0.05 in stepping test, initiation time, postural balance test). INTERPRETATION & CONCLUSION: Our results demonstrated that melatonin acted as an effective neuroprotective agent for striatal dopaminergic neurons in 6-OHDA lesioned rat model of Parkinson's disease.