Melatonin improves locomotor deficits and protects dopaminergic neurons. A, Negative geotaxis assay of adult flies exposed previously for 7 d to 125 μm rotenone, 5 mm melatonin, or both, compared with control flies maintained in the absence of drugs. Representation is the same as that in Figure 1 A. B, Quantification of dopaminergic neurons in brains of control flies exposed or not exposed for 7 d to 5 mm melatonin (M) and in flies exposed for 7 d to 125 μm rotenone (R) with or without 5 mm melatonin. n indicates the number of brain hemispheres examined in each condition. ^*p < 0.05, ^**p < 0.01, and ^***p < 0.001 compared with flies exposed to rotenone without melatonin.