Fig. 5.

Synaptic triads are associated with both serotonin and nonserotonin neurons. (A) Quantitative analysis of VGLUT1–3 and GAD2 axons (paired with synapsin) related to TPOH-labeled processes. Both VGLUT2- and GAD2-containing axons are the most common types of axons in association with serotonin neurons, consistent with their overall abundance in the neuropil (n = 3 rats; *P < 0.001 vs. either VGLUT1 or VGLUT3). (B) The rate that VGLUT1–3–GAD2 pairs are adjacent to serotonin neurons is proportional to their overall abundance in the neuropil (*P < 0.001 vs. VGLUT1 or VGLUT3), and therefore triads appear to involve both serotonin and nonserotonin neurons. Bars represent SEM.