You probably don't want to find out if 4,5-dihydroxy-DMT can get in the brain. Dihydroxylated tryptamines tend to be neurotoxic to monoamine neurons. They are transported into cells and autoxidized to cytotoxic diquinone derivatives. The best known examples are 5,6-dihydroxytryptamine and 5,7-dihydroxytryptamine, but 4,5-dihydroxytryptamine is also apparently neurotoxic.
DMT derivatives can be tranported into serotonergic neurons, so dihydroxylated derivatives of DMT are potentially neurotoxic.