sex difference and effects of gonadal hormones on thermal pain thershold in rat

Abstract

Various clinical and experimental studies indicate that gonadal hormones exert modulatory effects on nociception and analgesia.The aim of the present study was to investigate the role of gonadal hormones in the response by male and female rats to thermal nociceptive stimulation.Materials and Methods. 7 week old albino (Wistar) rats were used in our study. Animals were randomly divided into control, sham and ovariectomised or orchidectomised groups. Thermal pain threshold was measured through tail immersion test before and 10, 20 or 40 days after gonadectomy. The pain threshold was measured as the time required to elicit a flick of the tail called analgesia time. Serum testosterone, estradiol, progesterone or prolactin levels were measured simultaneously.The results showed that analgesia time was higher in female (5.11 min) than in male (4.93 min) intact animals (p<0.05) indicating sex difference in response to thermal nociception. Serum testosterone, estradiol or progesterone level as well as analgesia time were not significantly reduced 10 days after gondectomy. In male animals, analgesia time was significantly decreased (p<0.01) 20 or 40 days after orchidectomy (2.25 or 2.14 min, respectively) compared with control rats (4.93 min). Serum testosterone concentration was significantly reduced (p<0.05) 20 or 40 days after orchidectomy (0.08 or 0.09 ng/mL, respectively) compared with control serum testosterone level (2.14 ng/mL). In female rats, analgesia time was significantly decreased (p<0.001) 20 or 40 days after ovariectomy (2.87 or 2.66 min, respectively) compared with control rats (5.11 min). Serum estradiol concentration was significantly reduced (p<0.001) 20 or 40 days after ovariectomy (3.17 or 0.87 ng/mL, respectively) compared with control serum estradiol level (19.95 ng/ml). Serum progesterone level was also decreased (p<0.001) 20 or 40 days after orchidectomy (5.27 or 0.55 ng/mL, respectively) compared with control serum estradiol level (17.66 ng/mL). Serum prolactin level was not significantly enhanced during experiment indicating that there was not heat stress influencing the procedure.Conclusively, our findings clearly indicate that depletion of gonadal hormones 20 or 40 days after gonadectomy modulates the pain-induced behavioral responses related to thermal nociception.

Painful Diabetic Neuropathy in Type II Diabetic Patients: Evaluation with Different Diagnostic Modalities

“…Previous experimental and clinical studies have confirmed a close relationship between sex steroids and pain modulation. (32,33,34). Neuropathic pain has been found more prevalent in women than in men in representative samples of general population (35,36).…”