Supplementary Figure 4: Synaptic interactions between BF cell types measured in brain slices.
a. ChAT → VGLUT2 connections. Left, responses of an example VGLUT2+ neuron to activation of ChAT+ neurons by a single 5-ms pulse of blue light (cyan dot) and a train of 5 pulses (10 Hz). Right, responses of another VGLUT2+ neuron (same as in Fig. 5c) before (blue) and after successive blockade of GABAA receptors (brown), mAChRs (red), and nAChRs (black). These pharmacological experiments indicated that the large, prolonged inhibitory response was mediated not by GABAA receptors but by mAChRs, and the small transient excitatory response was mediated by nAChRs.
b. Diversity of ChAT → SOM connections. Left, an example SOM+ neuron exhibiting fasting spiking in response to depolarizing current injection and fast excitatory response evoked by light activation of ChAT+ neurons. Right, another SOM+ neuron with low-frequency spiking evoked by current injection and slow inhibitory response to ChAT+ neuron activation.
c. Lack of PV → ChAT input. Left, confocal image of BF slice showing presynaptic PV+ neurons expressing ChR2-mCherry (red) and postsynaptic ChAT+ neurons expressing eGFP (green). Upper right, reliable spiking of an example PV+ neuron evoked by a light pulse (5 ms) or light step (200 ms), recorded with cell-attached recording. Lower right, whole-cell recording from an example ChAT+ neuron showing many spontaneous IPSCs but no light-evoked response. The recording was made under voltage clamp at 0 mV.
