ObjectiveTo investigate the expressions of substance P (SP) and neurokinin-1 receptor (NK-1R) in the posterior horn of the L5－S2 spinal cord in the rat model of chronic nonbacterial prostatitis (CNP) at different time points of modeling.

METHODSForty adult male SD rats were randomly divided into four groups of equal number, control, 45 d model, 60 d model, and 90 d model, and proteins were obtained from the prostatic tissue of another 30 rats. The CNP model was made by intraperitoneal injection of 0.5 ml DPT vaccineand intradermal injection of mixed solution of 1 ml prostatein extract and complete adjuvant at a 1∶1 ratio, while the control rats were injected with the same volume of normal saline. At 45, 60, and 90 days after modeling, we measured the paw withdrawal threshold (PWT) of the rats, determined the levels of TNF-α, IL-1β, IL-2, and IL-10 in the prostate tissue by ELISA, observed the histomorphological changes in the prostate by transmission electron and light microscopy, and detected the expressions of SP and NK1-R in the L5－S2 spinal cord by immunohistochemistry.

RESULTSThe model rats showed significantly increased sensitivity to pain, with remarkably lowered PWT at 45, 60, and 90 days after modeling. The levels of TNF-α, IL-1β, IL-2, and IL-10 in the prostate tissue were markedly elevated in the CNP models as compared with those in the controls (all P<0.05), most significantly at 90 days (all P<0.05). Immunohistochemistry showed that the expressions of SP and NK-1R were remarkably higher in the CNP model groups than in the control (all P<0.05), the highest at 90 days. Light microscopy revealed no inflammatory cell infiltration in the prostate tissue of the control rats, and obvious edema and increased lymphocytes were observed with the prolonged time of modeling.Transmission electron microscopy showed inflammatory changes in the prostate tissue of the model rats and that peritubular interstitial edema was most obvious at 90 days, with widened intervals between peritubular cells and the epithelial base and increased numbers of fibroblasts and collagen fibrils.

CONCLUSIONSThe synthesis of SP and the level of NK-1R were increased in the posterior horn of the L5－S2 spinal cord in the rat model of CNP.