Extended Data Fig. 1: Somatostatin cells form a shell around a calbindin-rich central core of the somatosensory TRN; nearly all neurons in the somatosensory TRN express parvalbumin.
From: Two dynamically distinct circuits drive inhibition in the sensory thalamus
a, Epifluorescence images showing serial sections of live tissue expressing AAV9-DIO-GFP (9 days of expression) through the TRN of two P23 SOM-Cre mice. Anterior-posterior (AP) positions of the sections relative to bregma are indicated. Notice how the SOM cells form a shell-like structure surrounding the central core of the somatosensory TRN (centred ~ −1.4 mm from bregma) (experiment replicated 12 times). b, Top, dot plots showing the locations of the genetically or immunohistochemically labelled TRN cell types for sections at different AP distances from bregma. Bottom, proportion of cells expressing PV, CB, SOM-Cre × tdT, and combinations of the markers. Quantification was restricted to the boxed regions shown in the top panels (cell counts: left, 947; middle, 1,075; right, 843; 3 sections from 3 mice). The proportion of CB cells was highest in the middle section of the somatosensory TRN (−1.4 mm), whereas the proportion of SOM-Cre × tdT cells was lowest in the middle section and higher in the more anterior and posterior sections (P < 0.001, χ2 test with Yates’ correction). Data are mean ± s.e.m. c, Left, confocal images of the somatosensory sector of TRN in a PV-Cre × tdT mouse (red) stained for NeuN (green). Right, quantification of expression. In PV-Cre × tdT mice, 98.09% of TRN neurons were double positive for tdT and NeuN, 0.73% were positive only for tdT, and 1.18% were positive only for NeuN (1,218 neurons, 2 sections, 1 mouse). d, Same as c but tissue was stained immunohistochemically for parvalbumin. In PV-Cre × tdT mice, 98.66% of TRN neurons were double-positive for tdT and PV, 0.34% were positive only for tdT and 0.34% were positive only for PV (1,177 neurons, 2 sections, 1 mouse). e, DIC-IR (left) and tdT fluorescence (right) images of TRN in a live slice from a PV-Cre × tdT mouse. Asterisk indicates a soma that did not express tdT. During such live imaging, tdT-negative somata were relatively rare in TRN (>80% of somata visualized in DIC-IR expressed tdT; n = 5 slices, 3 mice; right panel). f, All tdT-negative cells targeted for recording (n = 8/8) had physiological properties of glia. Left, TRN glial cells had hyperpolarized resting potentials (typically less than −85 mV) and no action potentials even during large depolarizations.
