(A) Example traces from recordings of representative CA and IS VIP-INs from Scn1a. VIP-Cre.tdT mice, as well as a PV-IN and pyramidal neuron from a Scn1a.PV-Cre.tdT mouse, before and after bath application of 1 μM Hm1a at a 3X rheobase (near maximal) current injection for each cell. Note that the horizontal scale for the PV-IN is 100 ms instead of 200 ms, to facilitate visualization of individual APs. (B) Change in the max steady state firing frequency of n = 9 CA VIP-INs, 7 IS VIP-INs, 6 PV-INs, and three pyramidal neurons from a total of 5 Scn1a.VIP-Cre.tdT and 2 Scn1a.PV-Cre.tdT P18-21 mice, with p values and significance determined using a paired students’ t-test. (C) Spike amplitude of successive APs elicited at 3X rheobase for each cell. Line and shaded area represent mean ± SEM, and bar indicates significance at p<0.01 via a multivariate ANOVA and post-hoc Bonferroni correction. (D) Example traces from voltage clamp recordings of VIP-INs from acutely dissociated cortex of P18 WT.VIP-Cre.tdT mice. Light gray shows the initial transient sodium current recorded with a single voltage command step from −80 mV to 0 mV. Black shows the response following bath application of 500 nM Hm1a. The dashed line indicates the inset (shown on the right). There is no change in the peak amplitude, but clear slowing of inactivation. (E) Example differential interference contrast image of a dissociated VIP-IN, as well as the tdT signal imaged with epifluorescence. VIP-INs had small bipolar or rounded shapes. Scale = 5 μM. (F) Quantification of the effects of Hm1a on n = 3 VIP-INs from 2 P18 WT.VIP-Cre.tdT mice. Purple lines represent the change of each individual cell, with p values determined by a paired students’ t-test.