Our previous single-unit recording studies (SFN Abstr. ’02, #482.16) showed that acute estrogens can potentiate the excitation of VMN neurons. To investigate underlying mechanisms, whole-cell patch voltage clamp was used to study VMN neurons in 300-µm hypothalamic slices prepared from 20 female juvenile (3-5 wks) rats. Voltage steps or ramp were applied every 5 min to evoke whole-cell currents. After baseline recording, the neuron was treated with estradiol (E2, 10 nM) or vehicle through bath for up to 15 min and then washed. In 13 of the 22 E2-treated cells, the peak inward currents were within the range of the vehicle group (n=8). In the remaining 9 units, the average peak inward current started to increase within 5 min and reached 149, 172 and 160% at 5, 10 and 15 min of E2 treatment, respectively. These values are significantly greater than the pretreatment level and the levels of either vehicle and or non-responsive cells at each time point (all p < 0.01). Opposite results were observed for outward cu...