title: Hypoglossal premotor neurons of the intermediate medullary reticular region express cholinergic markers.
abstract: The inspiratory drive to hypoglossal (XII) motoneurons originates in the caudal medullary intermediate reticular (IRt) region. This drive is mainly glutamatergic, but little is known about the neurochemical features of IRt XII premotor neurons. Prompted by the evidence that XII motoneuronal activity is controlled by both muscarinic (M) and nicotinic cholinergic inputs and that the IRt region contains cells that express choline acetyltransferase (ChAT), a marker of cholinergic neurons, we investigated whether some IRt XII premotor neurons are cholinergic. In seven rats, we applied single-cell reverse transcription-polymerase chain reaction to acutely dissociated IRt neurons retrogradely labeled from the XII nucleus. We found that over half (21/37) of such neurons expressed mRNA for ChAT and one-third (13/37) also had M2 receptor mRNA. In contrast, among the IRt neurons not retrogradely labeled, only 4 of 29 expressed ChAT mRNA (P < 0.0008) and only 3 of 29 expressed M2 receptor mRNA (P < 0.04). The distributions of other cholinergic receptor mRNAs (M1, M3, M4, M5, and nicotinic alpha4-subunit) did not differ between IRt XII premotor neurons and unlabeled IRt neurons. In an additional three rats with retrograde tracers injected into the XII nucleus and ChAT immunohistochemistry, 5-11% of IRt XII premotor neurons located at, and caudal to, the area postrema were ChAT positive, and 27-48% of ChAT-positive caudal IRt neurons were retrogradely labeled from the XII nucleus. Thus the pre- and postsynaptic cholinergic effects previously described in XII motoneurons may originate, at least in part, in medullary IRt neurons.
authors.affiliation: Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce St., Philadelphia, PA 19104-6046, USA.
authors.forename: Denys V
authors.initials: DV
authors.lastname: Volgin
authors.forename: Irma
authors.initials: I
authors.lastname: Rukhadze
authors.forename: Leszek
authors.initials: L
authors.lastname: Kubin
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002795:Choline O-Acetyltransferase / Q000032:analysis* / Q000235:genetics; D002799:Cholinergic Fibers / Q000737:chemistry*; D007002:Hypoglossal Nerve / Q000737:chemistry* / Q000166:cytology / Q000201:enzymology; D007150:Immunohistochemistry; D008297:Male; D008526:Medulla Oblongata / Q000737:chemistry* / Q000166:cytology / Q000201:enzymology; D009434:Neural Pathways / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D043585:Receptor, Muscarinic M2 / Q000032:analysis; D011976:Receptors, Muscarinic / Q000032:analysis* / Q000235:genetics; D012154:Reticular Formation / Q000737:chemistry* / Q000166:cytology / Q000201:enzymology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D015415:Biomarkers; D012333:RNA, Messenger; D043585:Receptor, Muscarinic M2; D011976:Receptors, Muscarinic; D002795:Choline O-Acetyltransferase
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