Effects of gonadectomy and pain on interferon-gamma production in splenocytes of male and female rats

The role of gonadal hormones and persistent pain (formalin test) in the reg ulation of interferon-gamma (IFN-gamma) production in splenocytes was inves tigated in male and female rats. Animals were either sham-operated (Intact) or gonadectomized (GDX) and, 3 weeks later, were subcutaneously injected w ith formalin (50 mul, 10%) or only pricked with a syringe needle in the dor sal hind paw. Sixty minutes after treatment the animals were deeply anesthe tized and the spleens were dissected under aseptic conditions. Blood was co llected from the abdominal aorta for measurement of plasma steroids. IFN-ga mma production was determined in vitro in the splenocytes after Con A stimu lation. Splenocytes of Intact females showed higher IFN-gamma production th an those of Intact males, This sex difference disappeared in GDX animals be cause of the lower levels in GDX females. Formalin decreased IFN-gamma in b oth Intact and GDX groups. In females, there was a positive correlation bet ween IFN-gamma production in splenocytes and plasma estradiol levels. The p resent data demonstrate a sex difference in IFN-gamma production (due to th e immunostimulating effect of estradiol in females) and an immunodepressive role of pain in both sexes. (C) 2001 Academic Press.