Isoflurane preconditioning neuroprotection in experimental stroke is male-specific. The role of androgens in the ischemic sensitivity of isoflurane preconditioned male brain and whether androgen effects are androgen receptor dependent were assessed. Male C57BL/6 mice were implanted with flutamide (androgen receptor antagonist), or castrated and implanted with testosterone, dihydrotestosterone, flutamide, letrozole (aromatase inhibitor), or vehicle 7-13 days before preconditioning. P450 estrogen aromatase wild-type and knockout mice were also evaluated. All mice were preconditioned for 4 h with 0% (sham preconditioning) or 1% isoflurane (isoflurane preconditioning) and recovered for 24 h. Mice then underwent 2 h of middle cerebral artery occlusion and were evaluated 22 h later for infarct volume. For neurobehavioral outcomes, sham and isoflurane preconditioned castrated male±dihydrotestosterone groups underwent 1 h of middle cerebral artery occlusion followed by 9 days of reperfusion. Isoflurane preconditioning neuroprotection relative to infarct volume outcomes were testosterone and dihydrotestosterone dose-specific and androgen receptor-dependent. Relative to long-term neurobehavioral outcomes, front paw sensorimotor function improved in isoflurane preconditioned mice regardless of androgen status while androgen replacement independently improved sensorimotor function. In contrast, isoflurane preconditioning improved cognitive function in castrates lacking endogenous androgens, but this improvement was absent in androgen replaced mice. Our findings suggest that androgen availability during isoflurane preconditioning may influence infarct volume and neurobehavioral outcomes in male mice following experimental stroke. Keywordsandrogens; testosterone; dihydrotestosterone; androgen receptor; neuroprotection; preconditioning Prior brain exposure to minor insults, chemicals, or pharmacological agents can "precondition" or increase the brain's tolerance to future, more injurious events. Anesthetics in particular may play an important and unique role as brain preconditioning agents because of their clinical use and relevance during the perioperative period for cardiovascular procedures and neurosurgical interventions. Perioperative stroke is a serious complication that can occur during or following * Corresponding author. Tel: +1-503-494-5735; fax: +1-503-494-3092. murphyst@ohsu.edu (S. J. Murphy). 1 Present address: Department of Neurology, The Affiliated Nanjing Benq Hospital of Nanjing Medical University, Nanjing, P R China 210019. 2 Present address: Department of Neurology at the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, P R China 210008. 3 These authors contributed equally to this work. NIH Public Access Author ManuscriptNeuroscience. Author manuscript; available in PMC 2010 August 1. (Selim, 2007). Clinically, there is much interest in pharmacologically preconditioning the human brain with anesthetics and its impact on perioperative stroke, as anesthetic agents are kno...