FCPR03 Ameliorates CUMS-induced Depressive-like Behaviors In Mice Without Affecting The Dopaminergic System In Medulla

Objective:To evaluated the antidepressant-like effect of FCPR03 in the mice exposed to CUMS,and investigated the underlying mechanism.Rolipram was used as a positive control to assess the emesis effect and the underlying mechanism of FCPR03.We expected to discover a safe and effective PDE4 inhibitor to prevent and cure depression.Methods:(1)Behavioral tests included sucrose preference test(SPT),forced swim test(FST),tail suspension test(TST)and open field test(OFT)were carried out to evaluate the antidepressant-like effect of FCPR03 in the CUMS-treated mice.(2)After behavior tests,all mice were sacrificed and the tissue samples(especially hippocampus)were collected for biochemical assay.cAMP content in hippocampus were detected by ELISA,and protein expression of p-CREB,CREB,BDNF,p-Akt,Akt,p-GSK3?,GSK3?,DCX,PSD95 and Synapsinl were detected by Western-blot.The dendritic complexity and spine density in the hippocampus were analyzed by Golgi staining.(3)Combined injection of ketamine and xylazine to mice alternative model was performed to observe the duration of anesthesia,which was regarded as an endpoint to reflect the emetic effect betweem rolipram(1.0 mg/kg)and FPR03(1.0 mg/kg).Beagle dogs were treatment with different doses of FCPR03(1.0 mg/kg)and rolipram(1.0 mg/kg)to further validate the emesis effect.And the antagonistic effect of metocloxypramide(0.3 mg/kg)on the emesis induced by rolipram was studied.After chronic administration of drugs(14 days),all beagle dogs were sacrificed and tissue samples(especially medulla oblongata)were collected for biochemical assay.The contents of monoamines in the medulla of beagle dogs were detected by HPLC-ECD.The mRNA expression of 5-hydroxytryptamine(5-HT)and tyrosine hydroxylase(TH)in medulla was assessed by qPCR.The activity and content of TH in medulla was detected by ELISA,and protein expression of TH and dopamine transporter(DAT)was investigated using Western-blot.(4)Behavioral tests included SPT,FST,TST and OFT were carried out to evaluate the antidepressant-like effect of rolipram(1.0 mg/kg)+metoclopramide(0.3 mg/kg)in the mice exposed to CUMS.Results:(1)FCPR03 ameliorated CUMS-induced depressive-like behaviors in mice as demonstrated by increased sucrose preference index in SPT(p<0.01),and decreased the immobility time in the TST and FST(p<0.01),and FCPR03 produced no significant difference in the total locomotor activity number in the OFT(p>0.05).(2)The chronic treatment with FCPR03 increased cAMP(p<0.01)concentration in the hippocampus of CUMS-treated mice,then increased p-CREB,BDNF,p-Akt,p-GSK3?,DCX,PSD95 and Synapsinl(p<0.01)expression,but did not affect CREB,Akt,GSK3? and GAPDH expression,FCPR03 was effective in reversing CUMS-induced decreases of dendritic complexity(p<0.01)and spine density(p<0.01)as examined by Golgi staining.(3)Rolipram significantly shorten the duration of anesthesia in mice as compared with vehicle treatment,FCPR03 exhibited the same anesthesia effect with vehicle.The results of beagle dogs further showed that rolipram caused emesis in all beagle dogs,and reduced food intake(p<0.01)and body weight(p<0.01),but metoclopramide(0.3 mg/kg)antagonized the effect of rolipram.However,FCPR03 and vehicle had no significant emetic effects during 180 min observation period.FCPR03 without affecting the dopaminergic system in medulla.Rolipram and rolipram+metoclopramide also increased dopamine concentration(p<0.01),the mRNA expression,activity and content(p<0.01)of TH in medulla of beagle dogs,and decreased the protein expression of DAT.Compared with rolipram,rolipram+metoclopramide reduced mRNA and protein(p<0.05)expression of TH and dopamine concentration(p<0.05)in medulla of beagle dogs.(4)Rolipram+metoclopramide ameliorated CUMS-induced depressive-like behaviors in mice as demonstrated by increased sucrose preference index in SPT(p<0.01),and decreased the immobility time in the TST and FST(p<0.01,p<0.01,respectively),and mice treated with rolipram and metoclopramide displayed no difference in the total locomotor activity number in the OFT(p>0.05).Conclusion:FCPR03 produces antidepressant-like effect in mice exposed to CUMS.FCPR03 mainly increased synaptic plasticity,regulate and control depression emotion through activating cAMP/CREB/BDNF and cAMP/Akt/GSK3?signal pathway.FCPR03 without effected the dopaminergic system in medulla,but rolipram increased the activity and content of TH,and increased the content of dopamine in medulla.Metoclopramide antagonized the emesis effect of rolipram,and reversed the changes of dopaminergic system in medulla induced by rolipram.Rolipram+metoclopramide still produces antidepressant-like effect in mice exposed to CUMS.