Fig. 3
Direct excitation, but no disinhibition by ChAT-VIP neurons. a Example traces of postsynaptic responses in a rat L2/3 pyramidal neuron upon ChR2-mediated activation of ChAT-VIP interneurons with blue light (470 nm, 10 ms, 25 Hz, top trace). The postsynaptic responses were blocked by nAChR antagonists (MLA 100 nM and MEC 10 µM, grey trace). The majority of L2/3 pyramidal neurons did not show a response to ChAT-VIP neuron activation (light blue trace). Pie chart showing the percentages of L2/3 pyramidal neurons with nAChR-mediated postsynaptic response (dark blue) and without (light blue). b Example traces of L2/3 pyramidal neurons recorded at 0 mV receiving spontaneous GABAergic IPSCs. Five blue-light pulses were applied (25 Hz, 10 ms). c Comparison of spontaneous IPSC frequency in L2/3 pyramidal neurons before and after ChR2-mediated activation of ChAT-VIP interneurons with five blue-light pulses (25 Hz, 10 ms), (IPSC frequency pre-stimulus: 1.809 ± 0.389 Hz, post stimulus: 1.732 ± 0.411 Hz, p = 0.2310, paired t-test, two-tailed, t = 1.245, df = 16; n = 17; mean ± SEM). d AP profile of a rat mPFC L2/3 FS interneuron in response to somatic step current injection (+200 pA and −150 pA). e Left: Example traces (average of single 10 traces) of postsynaptic responses in an FS interneuron upon ChAT-VIP interneurons with blue light (470 nm, 10 ms, 25 Hz, top trace). Middle trace: example trace recorded at 0 mV showing absence of an IPSC (n = 0/6). Bottom traces: light-evoked postsynaptic currents (n = 4/6) in absence (blue trace) or presence of nAChR blockers (MLA 100 nM and MEC 10 µM, grey trace). Right: Summary plot of the postsynaptic current amplitudes and blocked by nAChR blockers. f AP profile of a L2/3 LTS interneuron. g As in (e) but for a rat mPFC L2/3 LTS interneuron. No GABAergic IPSCs at 0 mV were observed following light-evoked activation of ChAT-VIP interneurons (n = 0/8). A subgroup of LTS neurons showed light-evoked postsynaptic currents (n = 5/8) at −70 mV (blue trace) that was blocked by nAChR antagonists (MLA 100 nM and MEC 10 µM, grey trace). Right: Summary plot of the postsynaptic current amplitudes. Summary plots show averages ± SEM.
