Neurotransmitters Involved in Tourette Syndrome
The primary neurotransmitters implicated in Tourette syndrome are dopamine, glutamate, and gamma-aminobutyric acid (GABA), with emerging evidence for serotonin, norepinephrine, histamine, and acetylcholine involvement. 1
Core Neurotransmitter Systems
Primary Neurotransmitters
The most consistent evidence points to three major neurotransmitter systems:
Dopamine: The most extensively studied neurotransmitter in TS, with evidence showing reduced tonic extracellular dopamine levels alongside hyperresponsive spike-dependent dopamine release following stimulation 2. This dopaminergic dysfunction forms the basis for why dopamine-receptor antagonists (antipsychotics) effectively alleviate tics.
Glutamate: The major excitatory neurotransmitter shows significant alterations in TS. Recent high-field MRI spectroscopy at 7T demonstrated significantly elevated glutamate levels in the premotor cortex of children with TS compared to controls 3. Interestingly, increased premotor cortex glutamate was associated with improved selective motor inhibition in TS patients 3.
GABA: The primary inhibitory neurotransmitter is implicated in the pathophysiology, though findings are less consistent than for dopamine and glutamate 1, 3. The balance between glutamate and GABA within cortico-striatal-thalamo-cortical circuits appears critical.
Secondary Neurotransmitter Systems
Beyond the primary three, multiple other neurotransmitter systems contribute to TS pathophysiology:
- Serotonin: Genetic and gene expression studies support involvement of the serotonergic system 2
- Norepinephrine: Evidence from molecular genetic and functional imaging studies 4
- Histamine: Genetic work on a two-generation pedigree has opened new research pointing to histamine's role, representing a previously neglected neurotransmitter with potential for new treatment development 2
- Acetylcholine, endocannabinoids, and corticoids: Also implicated but with less robust evidence 4
Clinical Implications
The neurotransmitter profile directly informs treatment selection. The dopaminergic system's dominant role explains why antipsychotics remain the most efficacious medications 5, while alpha-2 agonists (affecting norepinephrine) provide a less potent but viable alternative 1, 5.
Important Caveats
- Dysfunction in dopamine metabolism during early development may lead to counter-regulations in other neurotransmitter systems, or vice versa 4
- The different neurotransmitter systems consist of multiple receptor subtypes that may mediate different effects on motor activity, explaining why patients respond differentially to selective agonists or antagonists 4
- Effects may be dose-dependent, adding complexity to treatment optimization 4
Anatomical Context
These neurotransmitter abnormalities occur within the cortico-striatal-thalamo-cortical (CSTC) circuits 1, 6, 3, which represent the neuroanatomical substrate for tic generation and the sensory premonitory urges that precede them.