Journal: Journal of Neurophysiology

Article Title: Diverse physiological properties of hypoglossal motoneurons innervating intrinsic and extrinsic tongue muscles

doi: 10.1152/jn.00478.2019

Figure Lengend Snippet: Anatomic mapping of the hypoglossal (XII) motor nucleus. A: schematic of a transverse medullary slice through the XII motor nucleus. B: two-dimensional depiction of the slice in A shows the hypoglossal nucleus (XIIn) and the fourth ventricle (4V), inferior olive (IO), and spinal trigeminal nucleus (5SP) for orientation. C: confocal image from a brain stem slice obtained from an animal in which Texas Red was injected into the intrinsic longitudinal (IL) fibers and FITC into the genioglossus (GG) fibers. An adjacent slide was stained with 4′,6′-diamidino-2-phenylindole (DAPI) to highlight the cells that comprise the borders of the fourth ventricle. The image showing the back-labeled motoneurons was overlaid on the DAPI-stained image before the photograph was captured. Note that the IL motoneurons (red) are more medial and dorsal than the GG motoneurons (green). D: map showing the rostral-caudal position of the labeled hypoglossal motoneurons (XIIMNs) in the left and right hypoglossal nucleus. IL motoneurons (red; n = 150) are distributed throughout the rostral-caudal extent of the nucleus, although there is a heavier concentration roughly 1 mm caudal to the compact formation of the nucleus ambiguous. Extrinsic motoneurons are concentrated in more caudal regions of the nucleus, although a few were found more rostrally. E: a rostral-to-caudal view, looking down on the XII nucleus. This map confirms the ventrolateral location of extrinsic relative to intrinsic XIIMNs.

Article Snippet: To label GG motoneurons, we injected 14 μL of Dextran conjugated to fluorescein isothiocyanate (FITC; Invitrogen) into the GG ( n = 3 animals: 2 males, 1 female), with the injection site dorsal to the anterior tip of the mandible ( ).

Techniques: Injection, Staining, Labeling, Concentration Assay