Tourette's may be linked to histamine levels

Treating Tourette's: Scientific American
Excerpts:
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Tourette’s syndrome is most pronounced in children. The physical and
vocal tics, which can alienate kids from peers, are difficult to treat.
First-line drugs are limited in their efficacy, whereas more effective
antipsychotics have many potential long-term side effects, including
weight gain and movement disorders. Investigators may be moving closer
to a new treatment option involving drugs that already exist.

Last year researchers identified a new gene mutation associated with
the disorder. Known mutations have only explained a small number of
Tourette’s cases, so the investigators, led by Matthew State,
co-director of the Yale Neurogenetics Program, studied a rare family in
which the father and his eight children all had Tourette’s. In these
family members, the gene involved in the production of histamine in the
brain was shorter than normal, generating lower levels of the compound,
which is involved in inflammatory response. State believes these lower
levels can cause tics, and he is looking for this and further
histamine-related mutations in other people with Tourette’s.

Now scientists have found parallels between this family and
histamine-deficient mice, which furthers the connection to Tourette’s.
Most individuals with Tour­ette’s have low prepulse inhibition, meaning
that they are more easily startled or distracted than the average
person, says Christopher Pittenger, director of the Yale OCD Research
Clinic. In May he was to pre­sent new data to the Society of Biological
Psychiatry that both this family and mice missing the histamine gene had
low prepulse inhibition and tics. Other experiments have shown that
histamine-boosting drugs decrease ticlike behaviors in mice.

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Drugs that increase histamine are already being tested to treat other
neurological conditions, as well as attention-deficit hyperactivity
disorder, which is often found in people with Tourette’s.