Objective

2

To observe the behavioral and pain threshold alterations， as well as the changes in indexes related to depression and pain in the serum and central system in mice stressed by maternal separation and chronic neuropathic pain， and explore the underlying mechanism of Wenyang prescription （WY）， Jieyu prescription （JY）， and Wenyang Jieyu prescription （WYJY） in improving depression and pain sensitivity.

Method

2

The birth date of mice was recorded as PD0. After birth， the mice were divided into a blank group and an experimental group. The neonatal mice in the experimental group underwent maternal separation in PD5-14 at 8 h·d

-1

. After ablactation， the mice were divided into a maternal separation group， a WY group （Erxian decoction， 5.84 g·kg

-1

）， a JY group （Xiaoyaosan， 12.00 g·kg

-1

）， a WYJY group （16.68 g·kg

-1

）， and a fluoxetine group （2.60 mg·kg

-1

）， with 15 mice in each group. Meanwhile， 15 male mice of the same age without maternal separation were assigned to the normal control group. Mice in the blank group and the maternal separation group were fed on a regular chow diet in PD21-PD90， while the remaining groups were fed on the corresponding drugs. In PD91， sciatic nerve ligation was performed to induce a model of maternal separation and chronic neuropathic pain. The open field test was used to observe the depression-like behaviors of mice in each group， and the mechanical and temperature pain thresholds were measured to detect the pain sensitivity of mice in each group. The serum levels of corticosterone （CORT）， substance P， and

β

-endorphin （

β

-EP） were determined by enzyme-linked immunosorbent assay （ELISA）， and the expression of the glucocorticoid receptor （GR） in the amygdala and

β

-EP protein in the hypothalamus was detected by immunohistochemistry. The mRNA expression levels of amygdala GR gene （Nr3c1）， FK506 binding protein 5 gene （FKBP5）， metabolic glutamate receptor 5 gene （GRM5）， and brain-derived neurotrophic factor （BDNF） were detected by real-time fluorescence quantitative polymerase chain reaction（Real-time PCR）.

Result

2

Compared with the blank group， the maternal separation group showed reduced stay time and total distance traveled in the 5-min open field test （

P

<

0.01）， reduced mechanical pain threshold （

P

<

0.01）， increased serum CORT and

β

-EP （

P

<

0.01）， declining FKBP5 mRNA expression （

P

<

0.01）， and increased hypothalamic

β

-EP expression （

P

<

0.05）. Compared with the maternal separation group， the groups with drug intervention showed prolonged stay time （

P

<

0.05，

P

<

0.01） and up-regulated pain thresholds to different degrees. The total distance traveled in the 5-min open field test increased in the WY group， the WYJY group， and the fluoxetine group （

P

<

0.05，

P

<

0.01）. The JY group showed decreased serum CORT （

P

<

0.01）， reduced

β

-EP ， and increased BDNF mRNA （

P

<

0.01）. Nr3c1 and GRM5 mRNA decreased in the WY group （

P

<

0.05，

P

<

0.01）. The WYJY group showed decreased serum CORT （

P

<

0.05）and decreased Nr3c1， GRM5， and BDNF

mRNA （

P

<

0.05，

P

<

0.01）. The levels of

β

-EP expression were elevated to different degrees in the groups with drug intervention， but the differences were not significant. The levels of GR expression in the WY group， the JY group， and the WYJY group increased （

P

<

0.05）.

Conclusion

2

WYJY can inhibit central pain sensitization and regulate hypothalamic-pituitary-adrenal gland （HPA） axis function by enhancing the expression of GR in the amygdala and inhibiting neuroplasticity and excitability in the amygdala to relieve depression-like behaviors and improve somatic hyperalgesia.