Relationship between the Plasma Testosterone Level and Pain Reaction Times in Male Rats

Male prepubertal (about 4 weeks old) Wistar rats were used to estimate the pain reaction times using the tail-flick and hot-plate models; the testosterone concentration in the blood plasma was measured in all the animals before the tests. The same sets of animals were kept for the next 4 weeks under standard conditions; the experiment was repeated, and pain reaction times were also evaluated in the 8-week-old rats with blood samples collected to determine the plasma testosterone level. The results showed significant (P < 0.01) increases in the pain reaction times in both pain models in pubertal animals observed in a parallel manner with a corresponding significant (P < 0.01) increase in the plasma testosterone level. Therefore, age and sex are important factors in the choice of animals in pain experiments.