Antidepressant-Like and Anxiolytic-Like Effects of ZBD-2, a Novel Ligand for the Translocator Protein (18 kDa)

Activation of translocator protein (18 kDa) (TSPO) plays an important role to mediate rapid anxiolytic efficacy in stress response and stress-related disorders by the production of neurosteroids. However, little is known about the ligand of TSPO on the anxiety-like and depressive behaviors and the underlying mechanisms in chronic unpredictable mild stress (UCMS) mice. In the present study, a novel ligand of TSPO, ZBD-2 [N-benzyl-N-ethyl-2-(7,8-dihydro-7-benzyl-8-oxo-2-phenyl-9H-purin-9-yl) acetamide] synthesized by our laboratory, was used to evaluate the anxiolytic and antidepressant efficacy and to elucidate the underlying mechanisms. ZBD-2 (3 mg/kg) significantly attenuated anxiety-like and depressive behaviors in the UCMS mice, which was blocked by TSPO antagonist PK11195 (3 mg/kg). Treatment of ZBD-2 reversed the decrease in biogenic amines (norepinephrine, dopamine, and serotonin) in the brain region of hippocampus in the UCMS mice. The decreases in TSPO, GluN2B-containing N-methyl-d-aspartate (NMDA) receptors, GluA1, p-GluA1-Ser831, p-GluA1-Ser845, PSD-95, and GABA(A)-a2 were integrated with the increases of CaMKII and iNOS levels in the hippocampus of the UCMS mice. ZBD-2 significantly reversed the changes of above proteins. However, ZBD-2 or PK11195 treatment did not affect the levels of GluN2A-containing NMDA receptors and the total levels of GAD67. Our study provides strong evidences that ZBD-2 has a therapeutic effect on chronic stress-related disorders such as depression and anxiety through regulating the biogenic amine levels and the synaptic proteins in the hippocampus.