OBJECTIVE Histamine H3 receptor (H3 R) was reported important in regulation of central nervous system disea ses.But less study was carried on cerebral ischemia.Here we demonstrated that inhibition of H3 R was protective against ische mia reperfusion injury through reinforcement of protective autoph agy.METHODS Transient focal cerebral ischemia model (MCAO) in mice and OGD/reperfusion injury on cultured rat cortical neurons were carried out.RESULTS Histamine H3R was upregulated after ischemia reperfnsion injury, and eitherinhi bition of H3 R by three antagonists (thioperamide, clobenpropit and A331440) or H3 R knock out attenuated ischemia repeffusion induced injury in mice, evidenced by lower cell injury and anti apoptosis in vivo and in vitro, which was rcversed by H3R agonist immepip in WT mice.Given that autophagy may inhibit cell ap optosis, we surprisingly found that autophagy was further activa ted by both H3 R knock out and inhibition after ischemia, and the neureprotective effects were significantly reversed by administra tion of 3-MA which is an autophagy inhibitor.Both siRNA of Atg7 gene on neurons and knock out of Atg5 gene on MEF cell lines were carried out to make sure again the importance of auto phagy in protection of H3 R inhibition.To explore the mechanism of regulation of H3 R induced neuroprotection, interestingly, we found that histamine was not involved in H3 R action.Further studies indicated that CLIC4 which was reported that lower ex pression led to up-regulated autophagy level interacted with H3R C-terminal tail consisting of amino acid 414-436 (H3RCT) was involved in the protection of H3 R inhibition through suppressing Akt/GSK3/mTOR signaling.Because inhibiting of H3R and CLIC4 interaction presented neuroprotection in cultured neurons against OGD reporfusion injury.CONCLUSION Taken to gether, the study demonstrated that upregulated H3 R expression during ischemia reperfusion was autophagy inhibitory through ac tivating Akt/GSK3/mTOR signaling.Inhibiting H3R inactivated the signaling by suppressing H3R and CLIC4 interaction, and then led to autophagy upregulated to protect cells against ische mia reperfusion injury, suggesting that H3 R may be an attractive clinical therapeutic target.