Extended Data Figure 2. TRIO applied to rat primary motor cortex.
a, Schematic of injection sites used for TRIO in rat MC (see Fig. 1c for details of the viruses). Two different C regions were tested: striatum or contralateral MC (cMC). b, c, Coronal section of rat MC stained with DAPI (blue). Starter pyramidal neurons projecting to contralateral MC (b) or striatum (c) (yellow, a subset indicated by arrowheads) can be distinguished from neurons receiving CAV-Cre and AAV-FLExloxP-TC (red) or GFP from RVdG (green). Bottom insets, coronal sections showing representative presynaptic GFP+ cells in somatosensory cortex (SC) or thalamus (Th). These data indicate that callosal-projecting neurons and striatum-projecting neurons in rat MC both receive direct synaptic input from somatosensory cortex and thalamus (n=2 for cMC C region; n=3 for striatum C region). d, e, Omitting CAV-Cre for TRIO in the rat also resulted in local non-specific infection of RVdG. On average ~200 cells were observed (n=4) within 800 μm from the injection site in these control experiments. By comparison, 1392 GFP+ neurons were counted in the same region of a TRIO sample that has the lowest starter cells among the 5 brains analyzed. Scale, 100 μm. Error bars, s.e.m.