Detection of estradiol in rat brain tissues: Contribution of local versus systemic production.

•Developed and validated a UPLC–MS/MS method to measure estradiol levels in rat brain tissues.•Detected higher estradiol levels in specific regions of the brain than in serum in rats treated with different doses of estradiol benzoate.•Detected substantial levels of estradiol in specific regions of the brain in males even through serum estradiol levels were undetectable.•Letrozole treatment reversed differences between brain and serum estradiol levels, demonstrating that the differences were due to local estradiol production.