Expression of GDNF Receptors Within Nucleus Ambiguus During Rat Development

ABSTRACT Objective Upregulation of GDNF and its receptors is observed during laryngeal reinnervation after nerve injury. In contrast, little is known regarding the expression of GDNF receptors in the formation of the nucleus ambiguus (NA) and its innervation of the larynx during embryogenesis. Differences may suggest therapeutic targets after nerve injury. Study Design Laboratory experiment. Methods Rat brainstems at E14, E16, E18, E20, adult (4 animals/timepoint) were sectioned and stained for GDNF receptors: GFRα-1, GFRα-2, GFRα-3, and Ret. Islet1 and ChAT were used as markers for motoneuron cell bodies. Sections were observed using Zeiss Axio Imager M2 Microscope and quantified using Image J. Results Expression of all four GDNF receptors was identified within the nucleus ambiguus, as well as hypoglossal and facial nuclei of the adult rat brainstem. During rat development, GFRα-3 and Ret exhibited upregulation within the nucleus ambiguus at E14 whereas GFRα-1 began showing upregulation at E20. GFRα-2 exhibited no upregulation at embryonic timepoints. Conclusion: Upregulation of the GDNF receptors within the nucleus ambiguus occur after laryngeal muscles innervation during development and may associated with maturation and maintenance of the neuromuscular synapses of the larynx before and after birth. No differences among ambiguus, hypoglossal, and facial nuclei was observed.