Extended Data Fig. 1: Lateral habenula input fails to recruit strong disynaptic inhibition onto 5-HT neurons located in the ventromedial portion of DRN.

a, Experimental setup for panels b-g. Schematic showing viral expression strategy (left), confocal images showing CHETA-YFP and tdTomato expression in DRN (middle), and schematic of whole-cell patch clamp recording setup from SOM neurons, related to panels B and C (right). b, Example trace from CHETA-YFP-expressing 5-HT neuron recorded in voltage clamp, demonstrating photostimulation-evoked inward current. c, Example trace from CHETA-YFP-expressing 5-HT neuron recorded in current clamp, demonstrating photostimulation-evoked spiketrains at 20 Hz. d, Schematic of whole-cell patch-clamp recording setup from 5-HT neurons, related to panels E-G. e, Trial-averaged traces from an example 5-HT neuron, recorded in voltage clamp, illustrating photostimulation-driven currents at two holding potentials. Inset depicts zoomed region. f, Latency to peak outward current response at Vm = −40 mV across all photostimulation events (n = 120 events) for one example neuron. g, I-V curve for photostimulation-driven currents from one example neuron. h, Experimental setup for panels i-o. i, Trial-averaged trace from an example SOM neuron, recorded in voltage clamp, illustrating photostimulation-driven inward currents. Inset depicts zoomed region. j, Latency to peak inward current response across all photostimulation events (n = 615 events, 8 neurons). k, Amplitude of peak current response across all photostimulation events (n = 615 events, 8 neurons). l-m, Current-clamp traces from two example SOM neurons showing subthreshold responses to photostimulation (l) and suprathreshold responses to photostimulation (m). n, Classification of SOM responses to photostimulation across the population of recorded neurons. o, Peak depolarization from baseline for SOM neurons exhibiting subthreshold responses (n = 7 biological replicates). Line and shaded area express mean +- S.D.

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