I believe you're referring to glutamate, not glutamine though the two can be converted into the other. Glutamine is an amino acid though the two are so similar.
This neurotransmitter is something of a possible next frontier in psychopharmacological treatments. It's involved in all the mental illnesses but no one has yet been able to make a medication that exploits it for depression, psychosis, OCD, among other disorders.
I sat through a lecture with a notable researcher (and darnit I forgot his name) on future treatments for depression and he mentioned that he believes SSRIs have reached a saturation point where the market forces don't warrant pharmaceutical companies to make new ones. With equal efficacy with all SSRIs, several SSRIs available now for $4 a month, a good choice among them and other antidepressants, it's not cost-effective. Many of the upcoming meds for depression are merely planned to be a combination of buspirone (that costs $4 a month) with an existing SSRI that will likely cost a few hundred dollars a month, be given a flashy new name (Sexagasm, Benecrack, Cocajuana, Lucioushotbab) and be prescribed by doctors not bright enough to figure out it's just two $4 meds put into one.
This researcher mentioned that glutamate is the next obvious choice in developing a new antidepressant but the trick whenever a med was developed that worked on this NT, not one yet was been found to provide a benefit. Ketamine works on this NT and there is data suggesting it can provide psychiatric benefits though it's potential for abuse will make using it for such like holding the wolf by the ears.
In effect, the success of SSRIs may put an unintended roadblock to research new meds since the costs are expensive and the profit margins will not be as high.
