Hormonal reactions to fighting in rat colonies: prolactin rises during defence, not during offence.

Male Wistar rats living in colonies of 4 males plus 4 females were compared to noncolony males, cohabitating with a female. Irreversible dominance relationships developed between one dominant male (D) and three subordinates (S). Dominants developed high basal testosterone levels and large preputial glands.

Effects of LHRH antagonist administration to immature male rats on sexual development.

Gonadotropin secretion in immature male rats was inhibited by administration of a potent LHRH antagonist (LHRH-A): from 6 to 15 days of age (early onset/short-term treatment), from 6 to 48 days of age (early onset/long-term treatment) or from 22 to 31 days of age (late onset/short-term treatment). Balano-preputial separation was retarded by 9 or 13 days (short-term treatments) or by about 40 days (long-term treatment). Adult testicular weight was lowered and plasma FSH was increased after early, but not after late onset of LHRH-A treatment.