... higher rate of fibrillation, is opposite to the results obtained when a-synuclein wasincubated in the absence of MPTP. When a-synucleinwas incubated alone in the presence of dopamine, itled to inhibition ... solid line), in the presence of 100 lM neurotoxin (•, dotted line), in the presence of 200 lM neurotoxin ( , dottedline) and in the presence of neurotoxin and50 lM dopamine (h, dashed line). Modulation ... concentrations of MPP+, the rate of nucle-ation (formation of toxic protofibrils) is delayed butonce the nucleus is formed, the rate of fibrillation is accelerated. At a higher concentration of the...