I read about that study with great interest.
They found a family where the dad and all eight of his kids (all with TS) had a small genetic defect which caused them not to have enough histamine in their body. The researchers beleive that low histamine levels may be a cause of TS. Among other things, histamine is very important for healthy brain function and neurotransmission.
I was in touch with one of the authors of the article and he said that, as soon as they can, they will begin testing Histamine 3 receptor antagonists on adults with TS. These drugs are in late stage development and only affect histamine levels in the brain. It should be interesting to see what happens.
If one wanted to raise histamine levels themselves, they could (very carefully) supplement with the amino acid l-histidine, which converts into histamine. It would have to be done carefully, though, as histidine raises histamine all over the body, not just the brain. It's something I'm looking at for my son, that is, possibly supplementing with a tiny dose of histidine and slowly increasing it, watching for any side effects and co-supplementing with zinc as it can be depleted by too much histamine. There are other severe side effects from too high levels of brain histamine, so it's not something to be toyed with.