Figure 8.

Schematic of excitatory microcircuits in the GL. A, Three glomerular output pathways are driven by ETCs. We have shown ETCs forming direct excitatory synapses onto lateral dendrite-bearing STCs, hSTCs. Asterisks indicate the other two output pathways mediated by ETCs found by previous studies: MCs are driven by the OSN-ETC-MC circuit (Hayar et al., 2004a,b, 2005; Murphy et al., 2005; De Saint Jan et al., 2009; Najac et al., 2011; Fukunaga et al., 2012; Gire et al., 2012), and TCs are excited by VGLUT3⁺ ETCs (Tatti et al., 2014). B, Two intraglomerular circuits are mediated by ETCs. In agreement with other studies, we find that ETCs form excitatory connections onto other ETCs (Hayar et al., 2005). Furthermore, we have shown direct excitatory synapses of ETCs onto UGCs. C, Two intraglomerular circuits are mediated by lateral dendrite-bearing STCs, hSTCs. We found excitatory microcircuits of hSTCs onto MCs and UGCs, indicating that, next to ETCs, hSTCs are a second excitatory element of the glomerulus.