The dopaminergic pathways mesocorticolimbic, nigrostriatal and tuberoinfundibulnar are mostly unmyelinated. Would it be plausible to infer the trajectory of these pathways using CSD given the fact that these fibers does not contain myelin?
The short answer is that unmyelinated cells are surrounded by lipid bilayer membranes that are sufficient to reduce, possibly prevent movement of water molecules. Hence tractography is possible in the absence of myelin. For more information see for instance: