Most of virgin male mice do not care but attack the pups. Interestingly, father mice care the pups rather than attack. This means that the experience of mating, staying with female mice and derivery change the behavioral pattern of male mice. However, the neural mechanisms of the different behavioral pattern between virgin and father mice was not elucidated. Accumulated evidences indicate that the medial preoptic area (MPOA) plays important role in parental behavior. In addition, we recently reported that the decreased number of c-Fos positive neurons induced by pup exposure in the posterior division of bed nucleus of stria terminalis (pBNST) in father mice compared with those in virgin male mice. In this study, we compared the electrical property of the pBNST neurons between virgin and father mice. We performed whole cell patch clamp recording to monitor the amplitude of evoked postsynaptic potentials. We observed the increased amplitude of the evoked inhibitory postsynaptic potentials (eIPSPs) in the pBNST in father mice compared with virgin male mice. Next, we demonstrated pharmacological lesion of the MPOA. Afther 4-7 days after the surgery, we prepared brain slice. Although lesion of the MPOA did not affect the amplitude of eIPSP in pBNST derived from virgin male mice, increased inhibition in the pBNST derived from father mice was abolished. These data suggest that decreased activity of the pBNST neuron in father mice is due to the increased inhibition which is related to the MPOA activity.