Three to four-week-old mice were anesthetized (1.5 % isoflurane) and then placed on a rodent stereotactic apparatus supplied with a mouse adapter (Stoelting, Wood Dale, IL). To identify STTn, a retrograde tracer (1% FAST-DiI in 10% ethanol; Invitrogen, Carlsbad, CA) was injected into the ventrobasal thalamus using a 5 μL Hamilton syringe needle. Coordinates of the injection site relative to bregma were: 1.48 mm posteriorly, 1.37 mm laterally, and 3.3 mm deep into the brain using the adjusted ratio of bregma-lambda distance specific for young mice (4.5 mm)14 (link). Dye was allowed 5-7 days post injection to be transported to the lumbar spinal cord, after which the mice were euthanized for spinal cord slicing and patch clamp recording.