Objective: To investigate the correlation between the behavioral performance and the expressions of substance P (SP) and neurokinin-1 receptor (NK-1R) in the posterior horn of the L5－S2 spinal cord in rats with chronic prostatitis (CP).
Methods: A CP model was made in 30 adult male SD rats by intraperitoneal injection of 0.5 ml dyphtheria pertussis tetanus (DPT) vaccine and mixed solution of 1 ml prostatein extract and complete adjuvant in a 1∶1 ratio, and another 10 rats were injected with the same volume of normal saline as controls. At 45 (n = 10), 60 (n = 10) and 90 days (n = 10) after modeling, the behavioral changes of the rats were observed by open-field and sucrose consumption tests, the prostatic indexes and levels of serum TNF-α, IL-1β, IL-2 and IL-10 were obtained, and the expressions of SP and NK1-R in the L5－S2 spinal cord were determined by immunohistochemistry.
Results: Compared with the controls, the CP model rats showed obviously decreased horizontal and vertical movement scores and sucrose consumption, particularly in the 90 d group (P < 0.05), significantly reduced prostatic indexes in the 45 d, 60 d and 90 d groups (all P < 0.05), even lower in the 90 d than in the 45 d and 60 d groups (P < 0.05). Edema and lymphocytes were increased in the prostatic tissue with the prolonged time of modeling. The levels of serum TNF-α, IL-1β, IL-2 and IL-10 were markedly elevated in all the CP rats as compared with those in the controls (P < 0.05), and so were the expressions of SP and NK-1R in the L5－S2 spinal cord (P < 0.05), even more significantly in the 90 d than in the 45 d and 60 d groups (P < 0.05).
Conclusions: Rats with chronic prostatitis are characterized by behavioral manifestation of depression, increased levels of serum TNF-α, IL-1β, IL-2 and IL-10, and a time-dependent upregulation of the expressions of SP and NK-1R in the posterior horn of the L5-S2 spinal cord, which suggests a correlation between the behavioral performance and the expressions of SP and NK-1R in the L5－S2 spinal cord of the rats.
Keywords: behavioristics; neurokinin-1 receptor; rat; substance P; chronic prostatitis.