Effect of Psychosocial Stress on the Testosterone Concentration and Pain Perception in Male Rats

Animal models of psychosocial stress are a good model for studying stress-related behavioral and endocrinological disorders in humans. The aim of present study is to investigate the effect of psychosocial stress on plasma testosterone level and pain perception. In this experiment 74 male rats (200-250 g) and 20 female rats (200-300 g) were used. In experimental groups (S1,S2), subjects were exposed to the attacks of stimulus (dominant) rats once a day for 5 consecutive days (30 min VS 4 hr). In control groups, subjects and stimulus rats were housed in different rooms (C1) or in adjacent cages in a room (C2). Pain perception was assessed by means of the Tail flick test. Testosterone was measured by radio-immunoassay. SPSS V.11 statistical software was used for data analysis. One way ANOVA was used to evaluate the results. Psycho-social stress reduced testosterone concentration in subject groups (S1, S2). Tail flick latency decreased significantly in S2 subject group (TFL: 4.2±0.4 s) and C2 control group (TFL: 4.2±0.2 s) as compared to C1 control group (TFL: 5.9 ± 0.8s). In addition there was significant difference between two subject groups (p<0.01). There was no significant difference between subject group (S1) and control groups. This study shows that psychosocial stress decreases plasma testosterone concentration and this effect is independent of length of daily encounters. But the pain perception depends on the length of daily encounters (30 min encounters did not, whereas 4 hr daily encounters did result in hyperalgesia).