AimsPreconditioning is promising for treating cerebral ischemic stroke. Annexin A1 (ANXA1) is a homeostatic antiinflammatory mediator that participates in countering against ischemic injuries. We investigated whether chloral hydrate preconditioning (CH) exerts neuroprotection via regulation of ANXA1 in stroke. MethodsAdult male C57BL/6J mice or ANXA1 knockout (ANXA1(-/-)) mice were randomly allocated to control (NCH) and CH groups [2%, 6%, and 10% chloral hydrate (i.p.) 1h before the middle cerebral artery occlusion (MCAO)]. Neurological performances were evaluated by modified 7-point neurological scales and rotarod test. Cerebral infarction was analyzed by triphenyltetrazolium chloride (TTC) staining and MRI. The expression of ANXA1, pro-inflammatory (TNF-, IL-1, IL-6), and antiinflammatory (IL-4, IL-10, TGF-) cytokines was investigated by RT-PCR, western blot, and immunofluorescence. ResultsChloral hydrate preconditioning significantly improved the neurological outcomes and reduced the infarction and brain edema after ischemia. In addition, CH increased the expression of ANXA1 in the microglia, decreased the levels of TNF-, IL-1, and IL-6, while elevated the levels of IL-4, IL-10, and TGF- in the MCAO mice. Furthermore, both ANXA1 blocker Boc1 (5mg/kg, i.c.v.) or ANXA1 gene deficiency restrained the protective effects of CH against stroke. ConclusionsChloral hydrate preconditioning protects against ischemic injuries through upregulating the expression of ANXA1, and the followed antiinflammatory mechanisms.