Fig 1.
M084 exhibits antidepressant-like effects in mice.
(A) The chemical structure of M084. (B&C) M084 reduced immobility time in forced swim test (FST, B) and tail suspension test (TST, C). Amitriptyline, a known antidepressant, was used as a positive control (10 mg/kg, 2 hrs). (D-F) In locomotor activity test, mice treated with vehicle and M084 (10 mg/kg, 2 hrs) showed no difference over the average speed (D), distance in central area and total distance traveled (E), and time in central area (F). Results are presented as mean ± SEM. N = 10–12/group, * p < 0.05, ** p < 0.01.
Fig 2.
M084 exhibits anxiolytic-like effects in mice.
(A) In the light/dark transition test, M084 treatment (10 mg/kg, 2 hrs) resulted in an increase in the number of entries in the light chamber. (B&C) In elevated plus maze (EPM) test, animals treated with M084 had more entries in all areas (B) and spent more time in the open arms and central area and less time in the closed arms (C) as compared to those treated with vehicle. Diazepam, a known antianxiety agent, was used as a positive control (1.5 mg/kg, 2 hrs). Results are shown as mean ± SEM. N = 12/group, * p < 0.05, ** p < 0.01.
Fig 3.
Distribution of M084 in serum, brain and CSF of mice.
Serum, brain, and CSF samples were collected at 2 hours after treatment of M084 or vehicle. Concentrations of M084 were determined with LC-MS/MS analysis. (A) M084 can efficiently cross the blood-brain barrier at pharmacologically relevant doses (10 mg/kg, 2 hrs). Results are shown as mean ± SEM. (B) M084 calibration curve. Correlation coefficient = 0.999654, weighting factor = 1/x. (C-F) Representative LC–MS/MS chromatogram of blank brain sample, serum, brain and CSF, respectively.
Fig 4.
M084 treatment reverses the CUS-induced pathological behaviors.
(A) M084 (10 mg/kg, 2 hrs) and amitriptyline (10 mg/kg, 7 days) treatment decreased immobility time in the FST of CUS-exposed mice. (B) In novelty suppressed feeding test (NSFT), CUS increased the latency to feed, while M084 treatment reversed such an effect. (C-E) In locomotor activity test, mice subjected CUS displayed moderate changes over the average speed (C), distance traveled in central area and the total distance traveled (D), and time in central area (E). M084 treatment had no effect on these changes induced by CUS. Results are showed as mean ± SEM. N = 12/group, * p < 0.05, ** p < 0.01, *** p < 0.001.
Fig 5.
M084 treatment enhances BDNF-TrkB signaling in the prefrontal cortex (PFC).
(A&B) mRNA levels of BDNF and c-fos in hippocampus (A) and PFC (B) of vehicle and M084-treated mice. Amitriptyline was used as a control for known antidepressant. (C&D) mRNA levels of BDNF and c-fos in hippocampus (C) and PFC (D) of vehicle and M084-treated mice subjected to CUS. Control animals were treated with vehicle only without CUS. (E&G) Representative western blots for mature BDNF, p-AKT (S473), total AKT, p-ERK1/2 (T202/204), and total ERK1/2 of PFC (E) and hippocampus (G). (F&H) The statistical results of protein levels of mature BDNF (normalized to that of GAPDH), p-AKT (S473)/total AKT, p-ERK1/2 (T202/204)/total ERK1/2 in PFC (F) and hippocampus (H). For all bar graphs, results are normalized to the control group with only the vehicle treatment and shown as mean ± SEM. N = 6/group,* p < 0.05, ** p < 0.01.