Objective To investigate the effect of caspases-3 on doxepin-induced apoptosis in rat neurons.Methods The PC12 cells seeded in culture plates were randomly divided into 4 groups (n =10 each) using a random number table:normal control group (group C);doxepin group (group D);caspase-3 inhibitor Z-DEVD-FMK group (group Z);doxepin + Z-DEVD-FMK group (group DZ).In group C,the cells were continuously incubated for 24 h.In group D,doxepin was added with the final concentration of 120 μmol/L,and the cells were continuously incubated for 24 h.In group Z,Z-DEVD-FMK was added with the final concentration of 10 μmol/L,and the cells were continuously incubated for 24 h.In group DZ,doxepin and Z-DEVD-FMK with the final concentrations of 120 and 10 μmol/L,respectively,were added,and the cells were continuously incubated for 24 h.After 24 h of incubation,the cell viability was detected by methyl thiazolyl tetrazolium assay,the cell morphology was observed under inverted microscope,and the neuronal apoptosis was measured by flow cytometry.Apoptosis rate was calculated.Results Compared with group C,the cell viability was significantly decreased,and apoptosis rate was increased in D and DZ groups (P＜0.01),and no significant change was found in the parameters mentioned above in group Z (P ＞ 0.05).Compared with group D,the cell viability was significantly increased,and apoptosis rate was decreased in group DZ (P＜ 0.01).The morphological changes were significantly mitigated in group DZ as compared with group D.Conclusion Caspases-3 may mediate doxepin-induced apoptosis in rat neurons.

Objective To evaluate the effect of doxepin on the expression of p38 mitogen-activated protein kinase (p38 MAPK) in the spinal cord of rats with neuropathic pain (NP).Methods Sixty clean-grade male Wistar rats in which intrathecal catheters were successfully implanted,weighing 200-250 g,were divided into 3 groups (n =20 each) by a random number table method:sham operation group (S group),NP group and doxepin group (D group).NP was induced by chronic constriction injury (CCI) to sciatic nerve.Doxepin 20 mmol/L (10 μl) was intrathecally injected at 3,7,14 and 21 days after CCI (T1-4) in group D.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 1 day before CCI (T0) and at T1-4.The rats were sacrificed after measurement of pain threshold at T4,and L4-6 segments of the spinal cord were removed for determination of the expression of p38MAPK protein by Western blot.Results Compared with S group,MWT was significantly decreased and TWL was shortened at T2-4,and the expression of p38MAPK protein was up-regulated in NP and D groups (P＜0.05).Compared with NP group,MWT was significantly increased and TWL was prolonged at T2-4,and the expression of p38MAPK protein was down-regulated in D group (P＜0.05).Conclusion The mechanism by which doxepin mitigates NP is related to down-regulating p38MAPK expression in the spinal cord of rats.