Additional studies using (+)-naltrexone to block Toll-like receptor 4 (TLR4) or a PPARΥ (peroxisome proliferator-activated receptor gamma) agonist, rosiglitazone, have also been reported to enhance M2 microglial polarization, leading to enhanced neuroprotection and improved cognitive outcome after cardiac arrest and intracerebral hemorrhage [84, 85]. This evidence concerns the gene TLR4 and cardiac arrest.