Upregulation of heme oxygenase-1 expression may facilitate memory and learning in mice

Heme oxygenase (HO)-1 is highly expressed in the hippocampus. Its expression is induced by many factors including hemes, whose metabolites play an important role in neuron protection and learning development. In the present study, the correlation between HO-1 and learning ability was investigated in mice. Behavioral tests were used to evaluate the effects of altering HO-1 on learning ability in mature mice. In order to determine the function of HO-1 in the immature mice, a dark-reared model was constructed. Either the HO-1 inducer hemin or the HO-1 inhibitor Zn protoporphyrin IX (ZnPPIX) was injected into the left lateral ventricle prior to a behavior test. Results showed that neither hemin nor ZnPPIX affected the learning ability of adult mice reared in normal conditions. The hippocampal HO-1 of dark-reared mice was decreased while it was increased in the behavioral training group. In general, HO-1 had no effect on established learning ability but it may be upregulated by behavioral training and is beneficial for the development of memory and learning ability in neonatal mice.