Effects Of Transection Of The Cervical Sympathetic Trunk On The Depression-like Behaviors In A Rat Model Of Chronic Unpredicted Mild Stress And The Tryptophan Metabolism Related Mechanism

The World Health Organization reports that the incidence of depression in the world is17%. Depression is a serious threat to human health, easily leading to suicide, and hasbecome the third largest disease burden in the world. The current clinical antidepressantshave a long onset time with low efficiency and more side effects.Stellate ganglion block (SGB) is a neuromodulation therapy with simple operationand mild side effects. Studies have shown that SGB exerts a good therapeutic effect forinsomnia, post-traumatic stress disorder, etc. however it remains unclear whether SGB alsohas a good therapeutic effect for depression. Chronic unpredictable mild stress (CUMS)model is a recognized animal model of depression research. Transection of cervicalsympathetic trunk (TCST) for rats can simulate SGB for human. This study aimed toobserve the changes in depression-like behaviors and tryptophan metabolism in thehippocampus and prefrontal cortex after TCST in CUMS rats.Part one Establishment of the rat model of chronicunpredictable mild stressObjective To establish and evaluate the rat depression model of CUMS.Methods Sixteen male SD rats, weighing200-220g, were randomly divided intocontrol group (C group) and stress group (CUMS group)(n=8). The rats in the C group didnot receive relevant stress and the rats in the CUMS group received two differentunpredictable stressors daily for28d. Rats’ body weight were recorded weekly and thesucrose preference test was performed weekly. The forced swimming test was performedafter CUMS for28d. Results Compared with the C group, the weekly body weight gain and sucrosepreference percentage were significantly decreased in the CUMS group (P<0.05). Theimmobility time was significantly increased in the forced swimming test after CUMS for28d (P<0.05).Conclusion The CUMS can establish a rat depression model. Part two Effects of transection of the cervical sympathetictrunk on the depression-like behaviors in the ratmodel of chronic unpredictable mild stressObjective To observe the effects of TCST on the depression-like behaviors in therat model of CUMS.Methods Thirty-two male SD rats were randomly divided into four groups: controlgroup (C group), CUMS group, CUMS+sham group (Sham group) and CUMS+transection group (TCST group). Rats in the C group did not receive relevant stress, andrats in the CUMS group, Sham group and TCST group received two differentunpredictable stressors daily for28d. Then the cervical sympathetic trunk was exposedwithout transition in the Sham group, but with transection in the TCST group. Ratsreceived the forced swimming test on days1,7,14and21after operation; received theopen field test on days1and21; and received the sucrose preference test on day21.Results There was no significant difference in the total horizontal movementdistance among the four groups (P>0.05). Compared with the CUMS group, there was nosignificant difference in the sucrose preference percentage in the Sham group (P>0.05).Compared with the Sham group, the sucrose preference percentage in the TCST group wassignificantly increased on day21(P<0.05). Compared with the CUMS group, theimmobility time in the forced swimming test had no significantly difference in the Shamgroup on days1,7,14and21(P>0.05). Compared with the Sham group, the immobilitytime in the forced swimming test had no significantly difference in the TCST group on day1(P>0.05), and was significantly decreased on days7,14and21(P<0.05).Conclusion The TCST can ameliorate the depression-like behaviors in the CUMS rats. Part three Effects of transection of the cervical sympathetictrunk on the brain tryptophan metabolism in the ratmodel of chronic unpredictable mild stressObjective To observe the effects of transection of the cervical sympathetic trunk onthe brain tryptophan metabolism in the rat model of chronic unpredictable mild stress.Methods On day21after TCST, the rats were sacrificed and the hippocampus andprefrontal cortex were departed from brain. The levels of tryptophan (TRP), kynurenine(KYN) and serotonin (5-HT) in the hippocampus and prefrontal cortex were detected byenzyme linked immunosorbent assay.Results Compared with the CUMS group, there was no significant difference in thelevels of TRP,5-HT and KYN in the hippocampus and prefrontal cortex in the Sham group(P<0.05). Compared with the Sham group, the TRP and5-HT levels were significantlyincreased and the KYN level was significantly decreased in the TCST group (P<0.05).Conclusion The TCST affects the TRP metabolism that probably exerts itsantidepressant effects. Part four Preliminary observation of the efficacy of the stellateganglion block for depression treatmentObjective To observe the efficacy of SGB on the depressive patients.Methods Seven depressive patient with disease course of2-20years received1-4kinds of antidepressants for2-20years. The patients received SGB treatment combinedwith general antidepressants. The drug description for SGB included1%lidocaine,0.5% 15-20times. The efficacy of SGB was evaluated by self-rating depression scale (SDS).Valid is regarded as SDS <50.Results The total treatment was118times for7patients, including Horner’ssyndrome or hoarseness and dysphagia appeared102times demonstrating the success ofSGB. No obvious adverse reaction occured. The SDS was significantly lower after thetreatment than that before the treatment. Among these, the use of antidepressant wasstopped without recurrence within three months in1case, the use of antidepressant wasreduced with recurrence within three months in2cases, the use of antidepressant was notchanged in3cases, and the follow-up was lost in1case.Conclusion SGB can effectively relieved the symptoms of patients with depression.