Fig. 5.

Apoptosis in spinal cord from Kir4.1−/− mice.A–C, Double-labeling of a spinal cord section of a Kir4.1−/− mouse (at P9) with Nissl (red;A) and TUNEL (green;B). Nissl strongly labels cytoplasm of large motoneurons located in the gray matter, contrasting the nuclei staining of glial cells in gray as well as in white matter. Note in the overlay (C) that predominantly small nuclei (glial nuclei) are TUNEL-positive. Additionally, most TUNEL-positive cells are located in white matter areas. D–F, Higher power magnification (inset of A) of part of the ventral horn of the gray matter shows that most large motoneurons are TUNEL-negative (arrows; closed arrowheadpoints to two weakly positive motoneurons), whereas small nuclei are strongly TUNEL-positive (open arrowheads), indicating that glial cells predominantly are undergoing apoptosis.G–I, Comparable WT section of the gray matter of the ventral horn. Sections were pretreated with DNase to induce DNA breakage. Small glial nuclei as well as large nuclei of motoneurons are strongly TUNEL-labeled (H).I, Overlay (arrows point to double-labeled large motoneurons). Scale bars: A–C, 200 μm; D–I, 50 μm.