Adult rats chronic unpredictable stress model of depression (CUS) was adopted to elucidate the antidepressant pharmacological activity and related neurogenesis protective effect of the total flavonoids extract (licorice flavonoids, LF) from the Glycyrrhiza uralensis Fisch. cultivated locally in Ningxia. The rats were exposed to 9 kinds of unpredictable sequence of stressors and were given flavonoids (300 mg x kg(-1), 100 mg x kg(-1) and 30 mg x kg(-1)) for 28 days. The antidepressant effect was elucidated by open field test, forced swimming test and tail suspension test. The level of serum corticosterone was detected by radioimmunoassay. 5'-Bromo-2'-deoxyuridine (BrdU) labeling experiments was employed to study the neurogenesis protective activities. The flavonoids can increase the sum of line crosses and number of rears, and decrease the number of fecal boli produced in the open field test of the CUS rats. Also the flavonoids can decrease the immobility time in forced swim test as well as in the tail suspension test. In addition, the flavonoids (300 mg x kg(-1)) can decrease the serum corticosterone level of the CUS rats, and increase the number of the new born BrdU positive progenitor cells at the subgranular zone (SGZ) of dentate gyrus (DG) region in hippocampus. The results demonstrated that the total flavonoids extract from the cultivated Glycyrrhiza uralensis Fisch. could produce the anti-depressive effect on chronic unpredictable stress of depression model rats and its mechanism may be associated with its neurogenesis protective effect.

OBJECTlVE To investigate the antidepressant effect and reIated mechanism of the totaI fIavonoids extract parts( Iicorice fIavonoids,LF)from Glycyrrhiza uralensisFisch. cuItivated IocaIIy in Ningxia. METHODS Forced swimming test( FST)and taiI suspension test( TST)were adopted to study the antidepressant pharmacoIogicaI effect in the acute stress-induced depression modeI in mice. The Km mice were intragastricaIIy administered with LF(5,30 and 180 mg·kg-1 )once daiIy,for 21 con-secutive days. One hour after the first,seventh and Iast administrations,the mice were submitted to FST by recording the immobiIity period within the Iast 4 min of the totaI 6 min in both tests and the resuIts were expressed as decrease in immobiIity period with respect to vehicIe controI. In TST,the other group of Km mice was used to evaIuate the antidepressant effect in same protocoI. In the antagonism of reserpine-induced symptoms test( ART),ICR mice were administered intragastricaIIy with LF( 50,150 and 400 mg·kg-1 )once daiIy for 7 consecutive days. One hour after the Iast administration,the mice received reserpine(4 mg·kg-1 ,ip),and ptosis or akinesia was measured 1 h after reserpine injection whiIe rectaI temperature was measured 4 h after the reserpine injection respectiveIy. The same protocoI was adopted in yohimbine toxicity potentiation test(YTT)as in ART. Thirty minutes fter the Iast adminis-tration,the mice received the threshoId IethaI dosage of yohimbine(30 mg·kg-1 ,sc)respectiveIy,and the death number of the mice was caIcuIated in 24 h after the yohimbine administration. In the 5-hydroxy-L-tryptophan(5-HTP)induced head-twitches test(HTT)in mice,after being administered intragastricaIIy with LF(50,150 and 400 mg·kg-1 )once daiIy for 7 consecutive days,the mice received pargiIine (100 mg·kg-1 ,ip)the next day,and 30 min Iater,5-HTP(10 mg·kg-1 ,ip)was intraperitoneaIIy injec-ted to induced the head twitch respectiveIy,and the times of head twitch in a 30 min period after 5-HTP treatment were observed at 6 time points. After HTT,the mice were sacrificed quickIy,and the mono-amine oxidase(mAO)activity in the brain cortex,hippocampus and thaIamus was examined to evaIuate the antidepressant effect of fIavonoids with mAO inhibition. RESULTS Compared with the vehicIe controI,LF significantIy decreased the immobiIity period in both FST and TST(P﹤0.05). LF(50,150 and 400 mg·kg-1 )antagonized the ptosis and akinesia symptoms respectiveIy in 1 h after reserpine administration( P ﹤ 0. 05 ), but faiIed to antagonize hypothermia produced 4 h after reserpine administration. AIso,at the same dosage,LF did not synergeticaIIy produce the enhancement of death by subcutaneous injection of yohimbine at the threshoId IethaI dosage. LF(150 and 400 mg·kg-1 )couId significantIy and synergeticaIIy increase 5-HTP induced head-twitches response(P﹤0.05),but LF couId not promote mAO activity in the cortex,hippocampus and thaIamus at the same dosage. CONCLUSlON LF exerts antidepressant-Iike effect on the modeI of acute despair test. The mechanism might be reIated to direct enhancement of the serotonergic neuraI function in the brain.