A, averaged AHPs and calcium transients from recorded neurons in the presence of 5 mm Cs+ for comparison between lactating and virgin rats. B, the peak amplitude of AHP was significantly larger in OT neurons during lactation, while such alteration was not observed among VP neurons. C, the peak ΔF/F amplitude did not increase significantly. D, the slow time constant of ΔF/F became significantly faster during lactation in both OT and VP neurons.