Figure 3.

Age‐related changes in synaptic inputs to lumbar spinal cord motoneurons (MNs). (A–P2) Sections were immunostained to identify cholinergic [vesicular acetylcholine transporter (VAChT)], glutamatergic [vesicular glutamate transporter 1 (VGluT1) and vesicular glutamate transporter 2 (VGluT2)], and GABAergic [vesicular GABA transporter (VGAT)] afferent synapses (green) and counterstained with fluorescent Nissl staining (blue) to visualize MN cell bodies. Graphs show the average density [(A, E, I, and M) number of puncta per 100 μm soma perimeter and (B, F, J, and N) size (in μm²)] of the different types of afferent terminals analysed. Representative confocal micrographs of (C1–D2) VAChT, (G1–H2) VGluT1, (K1–L2) VGluT2, and (O1–P2) VGAT terminals contacting (C1–C2, G1–G2, K1–K2, and O1–O2) adult and (D1–D2, H1–H2, L1–L2, and P1–P2) old MNs are shown. Data in the graphs are expressed as the mean ± SEM, ^* P < 0.05, ^** P < 0.01, and ^**** P < 0.0001 vs. adult (Student's t‐test); 50–60 MNs were analysed per animal (4–6 animals per age group). Scale bar in (P2) = 20 μm [valid for (C1–D2, G1–H2, K1–L2, and O1–P1)].