Despite extensive characterization of sex differ-ences in the medial preoptic area(mPOA)of the hypotha-lamus,we know surprisingly little about whether or how male and female mPOA neurons differ electrophysiolog-ically,especially in terms of neuronal firing and behavioral pattern generation.In this study,by performing whole-cell patch clamp recordings of the mPOA,we investigated the influences of sex,cell type,and gonadal hormones on the electrophysiological properties of mPOA neurons.Notably,we uncovered significant sex differences in input resistance(male＞female)and in the percentage of neurons that displayed post-inhibitory rebound(male＞female).Fur-thermore,we found that the current mediated by the T-type Ca2+channel(IT),which is known to underlie post-inhibitory rebound,was indeed larger in male mPOA neurons.Thus,we have identified salient electrophysio-logical properties of mPOA neurons,namely IT and post-inhibitory rebound,that are male-biased and likely con-tribute to the sexually dimorphic display of behaviors.