Figure 3: Sox14⁺ interneurons contribute to phasic and tonic inhibition in the dLGN.

(a) Flex switch strategy for delivering ChR2-EYFP into Sox14^cre/+ neurons illustrating the injection strategy. Image of ChR2-EYFP distribution in the LGN of an acute slice preparation. (b) Voltage (black) and current traces (grey) shown in response to brief 1 ms blue light pulses (blue) in a ChR2-expressing Sox14⁺ neuron. (c) The voltage trace obtained during current injection is from the cell shown in b. The plot on the left demonstrates the ChR2-evoked AP frequency at all LED stimulation rates with black filled symbols highlighting data from the cell shown in b. The doublet elicited with the initial photocurrent raised the expected AP frequency for this cell. The scatter plot compares the maximum AP frequency measured during current injection with the maximum AP frequency elicited by photocurrents. (d) Image showing a ChR2-eYFP-expressing cell (green) adjacent to a filled thalamic relay neuron (red). Scale bar, 30 μm. (e) Current traces recorded from a thalamic relay neuron during optogenetic stimulation. The black traces show light-evoked IPSCs. The bottom grey trace is recorded with all GABA_A receptors blocked. (f) Average ChR2-evoked IPSC recorded before (grey trace) and after DS2 application (black trace). The scatter plot illustrates the relationship between IPSC rise and decay for evoked IPSCs recorded from a thalamic relay neuron. (g) The top current traces were recorded from a thalamic relay neuron during optogenetic stimulation at 5 and 20 Hz. The current traces recorded from the same thalamic relay neuron are shown in the presence of 10 μM DS2. The bottom grey trace shows the gabazine block at 20 Hz stimulation rates. (h) Quantification of tonic conductance and IPSC response probability in the presence and absence of DS2. The shaded areas show s.e.m. (i) Voltage trace from a thalamic relay neuron during brief light pulses (blue) delivered at 1 and 20 Hz. Scatter plot quantifies the change in membrane voltage during 20 Hz optogenetic stimulation in all cells examined.