GPe inhibition of the three PPN cell types.
(A) Experimental set up to identify red ChAT+, Vgat+, and Vglut2+ PPN neurons for whole-cell patch clamp while stimulating ChR2-filled GPe axons [N=6]. (B) Example trace of the first five oIPSCs in the 2-second 20 Hz train [blue] inhibited by GABA-a receptor blocker, GABAzine [green], while holding the cell at –50mV. (C) Left, Percent connected among patched neurons in the rostral and caudal regions and, right, cell mapping of patched locations with the first oIPSC amplitude represented by the color scale. Top to bottom, i. ChAT+, ii. Vgat+, and iii. Vglut2+ datasets. (D) Average oIPSC amplitude at each of 40 optogenetic light pulses in n=6 ChAT+, n=19 Vgat+, and n=15 Vglut2+ caudal PPN neurons. (E) Left, Individual cell data for the first oIPSC amplitude and, right, example current traces. (F) Normalized current amplitudes in C. (G) Left, Individual cell data for the PPR between the first two oIPSC amplitudes in the train; p=0.0206. Right, top, example current trace of short-term synaptic facilitation in VgAT+ neurons. Right, bottom, example current traces of short-term synaptic depression in Vgat+ and Vglut2+ neurons. (H) Percent of pre-optical stimulation firing frequency [%Pre-Opto Frq] during and post-stimulation in n=25 ChAT+, n=18 Vgat+, and n=29 Vglut2+ caudal PPN neurons. (I) Individual cell data for the absolute change in frequency during stimulation [ΔFrq During Opto]. (J) Correlation analysis for Vgat+ neurons, color scale representing Spearman r [-1,1] and size representing p-value [1,0]. (K) Negative correlation between the absolute change in frequency during stimulation and first oIPSC amplitude; r=-0.627, p=0.044. (L) Correlation analysis for Vglut2+ neurons. (M) Negative correlation between the absolute change in frequency during stimulation and the pre-stimulation firing frequency; r=-0.648, p=0.014. *p<0.05, **p<0.01; box plots show median line with boxes showing IQR and whiskers showing 9th and 91st percentiles.