“Recent evidence suggests that the ubiquitous excitatory neurotransmitter glutamate is dysregulated in OCD, and that this dysregulation may contribute to the pathophysiology of the disorder.” “Nevertheless, the evidence supporting some important perturbation of glutamate in the disorder is increasingly strong.” Glutamate abnormalities in obsessive compulsive disorder: neurobiology, pathophysiology, and treatment. https://www.ncbi.nlm.nih.gov/m/pubmed/21963369/

“The researchers found that, compared to regular mice, those that lacked Sapap3 tended to have an overactive direct pathway, which would appear to explain why they are so prone to repeating the same actions over and over. Looking more closely at the rodents’ neural activity, the authors discovered that a particular chemical receptor called mGluR5 was constantly activated in the brains of OCD mice. This, in turn, increased the excitability of direct SPNs, leading the team to suspect that mGluR5 may well be the guilty party behind OCD, as it appears to control the hyperactivity of the brain circuits that coordinate action. Based on this discovery, the researchers injected the mice with a chemical that deactivates mGluR5 receptors, and rather incredibly found that their OCD behavior disappeared within minutes. “The reversibility of the symptoms was immediate – on a minute time frame,” explained study co-author Nicole Calakos in a statement.” http://www.iflscience.com/brain/brain-receptor-responsible-ocd-identified/

“There is strong evidence from family and twin studies that genetic determinants play an important role in the etiology of obsessive-compulsive disorder (OCD). In the only genome scan of OCD to date that we are aware of, suggestive linkage was reported to the chromosomal region 9p24, a finding that was subsequently replicated. This region contains the gene encoding the neuronal glutamate transporter, SLC1A1. SLC1A1 represents an excellent candidate gene for OCD based on evidence from neuroimaging and animal studies that altered glutamatergic neurotransmission is implicated in the pathogenesis of this disorder.” http://jamanetwork.com/journals/jamapsychiatry/fullarticle/209779

“It is timely to review the growing evidence from animal models and clinical research (e.g., brain imaging, genetics) on the role of the glutamatergic system in OCD. Emerging evidence from both animal models and clinical research (including brain imaging, neurogenetics) supports the glutamatergic system as a potential target for pharmacotherapy in OCD.”
Obsessive compulsive disorder and the glutamatergic system. Available from: https://www.researchgate.net/publication/258854482_Obsessive_compulsive_disorder_and_the_glutamatergic_system [accessed Oct 05 2017].

A selective review of glutamate pharmacological therapy in obsessive–compulsive and related disorders. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425334/