Effects and Therapeutic Use of TMS in Psychiatric Disorders: An Evidence-Based Review

Objective Recently we found that chronic immobilization stress (CIS) induced low levels of glutamate (Glu) and glutamine (Gln) and hypoactive glutamatergic signaling in the mouse prefrontal cortex (PFC), which was closely related with Glu-Gln cycle. Moreover, Gln-supplemented diet ameliorated CISinduced deleterious changes. In the present study, therefore, we investigated the effects of CIS and Gln supplementation on Glu-Gln cycle-related proteins to understand underlying mechanisms. Methods Using CIS-induced depression mouse model, we confirmed depressive behaviors caused by CIS and antidepressant property of Gln-supplementation with behavioral test and blood corticosterone assay. We examined expression of eleven proteins involving Glu-Gln cycle in the PFC. Results CIS decreased glutamate transporter 1 (GLT1), sodium-coupled neutral amino acid transporter (SNAT) 3, SNAT5, and mature SNAT2, suggesting excitotoxicity in synaptic cleft and shortage of Glu and Gln in astrocytes and neurons. Gln-supplementation did not affect non-stressed group, but significantly increased SNAT1 and SNAT3, which are the major Gln transporter in neurons and astrocytes respectively, as well as the mature SNAT2, implicating increasing transportation of Gln into neurons. Conclusion As a result, we confirmed that CIS disturbed Glu-Gln cycle toward shortage of Glu and Gln levels in astrocytes and neurons, but Gln supplementation changed Glu-Gln cycle toward facilitating translocation of Gln into neurons for glutamatergic signaling. Moreover, these results also supported the antidepressant property of Gln.