Severe childhood stress, such as child maltreatment, has been suggested to be a risk factor for depression and other psychiatric disorders in later life. In addition, women are statistically more likely than men to develop depression and anxiety disorders, suggesting a gender difference in stress sensitivity. However, the molecular mechanisms involved in stress-induced changes in neural activity during childhood and adulthood and the sex differences in these changes remain unclear. In the present study, we used a patch-clamp technique to analyze the effects of electric current stimulation of the foot at 3 weeks of age (3-week foot-shock, 3wFS) on membrane potential changes in pyramidal cells of the mature medial prefrontal cortex (mPFC) in mice. Analysis of female mice revealed no differences in resting membrane potential, input resistance, or action potential firing thresholds of mPFC pyramidal cells between the 3wFS and nonFS (no foot-shock) groups. The firing frequency of action potentials in mPFC pyramidal cells evoked by depolarizing current injection was increased in the 3wFS group compared to the nonFS group. Analysis of male mice showed no significant differences in any of the above parameters. Similarly, analysis of membrane potential changes in neurons of the dorsal raphe nucleus (DRN), one of the serotonergic primitive nuclei, showed no significant changes in either male or female mice. mPFC is an inhibitory regulator of the DRN, suggesting that in female mice subjected to juvenile stress, overexcitation of mPFC pyramidal cells may result in DRN inhibition. DRNs are strongly suppressed in female mice exposed to juvenile stress, which may contribute to sex differences in the onset of depression.