Variable colocalisation of GABAA receptor subunits and glycine receptors on neurons in the human hypoglossal nucleus.
The hypoglossal nucleus, the nucleus of the twelfth cranial nerve, is located dorsally in the midline of the medulla oblongata. The hypoglossal nucleus contains lower motor neurons which innervate the tongue muscles that control tongue movements involved in speech production, swallowing, mastication and associated respiratory movements. GABAA and glycine receptors are heteropentameric ionotropic receptors that facilitate fast-response, inhibitory neurotransmission in the mammalian brain and spinal cord. We investigated the immunohistochemical distribution of the GABAA receptor α1, α2, β2,3 subunits and glycine receptors as well as their relationship to the vesicular GABA transporter (VGAT) in the human hypoglossal nucleus at the light and confocal laser scanning microscope levels. The results showed that all of the GABAA receptor subunits as well as glycine receptor display punctate labelling indicative of synapses on the soma and dendritic membranes of large neurons within the hypoglossal nucleus. On average, approximately 50% of glycine receptors were co localised with GABAA receptor  α1 subunits. Also on average GABAA α2 and β2,3 subunits were colocalised with approximately 30% of glycine receptor subunits. VGAT positive terminals were associated with both GABAA and glycine receptor types. Both glycinergic and GABAergic positive puncta were found adjacent to VGAT terminal-like staining. These results suggest that inhibition of human hypoglossal motor neurons occurs not only through complex interaction of separated GABAAR and glycine receptor regions, but also through synapses containing both inhibitory receptor types co-existing at the same synaptic sites.
['Waldvogel|H J|HJ|', 'Biggins|F M|FM|', 'Singh|A|A|', 'Arasaratnam|C J|CJ|', 'Faull|R L M|RLM|']
D000328:Adult D000368:Aged D000369:Aged, 80 and over D005260:Female D006801:Humans D007002:Hypoglossal Nerve D008297:Male D008526:Medulla Oblongata D008875:Middle Aged D009046:Motor Neurons D009474:Neurons D011963:Receptors, GABA-A D018009:Receptors, Glycine
Receptors Subunits Glycine Hypoglossal nucleus GABA Confocal Antibodies Human brain Immunohistochemistry Microscopy XII cranial nerve nucleus