Fig. 3. Requirement of SERT expression in TCAs not SERT in cortical neurons for 5-HT uptake in the barrel cortex.

A. SERT (grayscale) and Vglut2 (green) double immunostaining of coronal sections of somatosensory cortex from P7 mice. Control SERT^fl/fl mice displayed two distinct classes of SERT+ fibers: fibers that were relatively thin, smooth and co-labeled with Vglut2+ TCA patches at layer 4 (L4) (strongly) and layer 6 (L6) (weakly), and fibers that were thick, punctated, randomly distributed as shown in enlarged views in third row images. No SERT immunostaining was discernible in SERT^Null mice. SERT immunostaining in Vglut2+ patches was not detectable in SERT^GluΔ but undiminished in SERT^CortexΔ and SERT^RapheΔ mice. SERT immunostaining in the thick fibers was dramatically reduced in SERT^RapheΔ, but undiminished in SERT^GluΔ and SERT^CortexΔ mice. B. 5-HT (grayscale) and Vglut2 (green) double immunolabeling of coronal sections of P7 somatosensory cortex. 5-HT immunostaining of Vglut2+ patches but not the thick fibers was dramatically reduced in SERT^GluΔ. 5-HT immunostaining of both the thick fibers and Vglut2+ patches in SERT^CortexΔ was indistinguishable from that in SERT^RapheΔ and control littermate mice. For each brain sample, SERT and Vglut2 double immunostaining (A) and 5-HT and Vglut2 double immunostaining (B) represent adjacent sections. Third row images show an enlarged view of SERT immunohistochemistry (A) or 5-HT immunohistochemistry (B) in areas outlined by red boxes on images in respective second row. Images for SERT^Null, SERT^RapheΔ and SERT^GluΔ cortices are reproduced from our previous study (Chen et al., 2015) for comparison of SERT and 5-HT immunostaining patterns in age-matched SERT^CortexΔ mice. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)