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A significant portion of Dbx1 neurons in the intermediate reticular formation are XII inspiratory premotoneurons
Author(s) -
Revill A,
Kottick A,
Akins V,
Vann N,
Gray P,
Del Negro C,
Funk G
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.1032.9
Subject(s) - glutamatergic , reticular formation , neuroscience , anatomy , chemistry , medicine , nucleus , biology , glutamate receptor , receptor
Reduced tonic and inspiratory drive to XII motoneurons (MNs) that innervate the genioglossus muscle (GG, a tongue protruder) is implicated in obstructive sleep apnea. Reduced excitability of glutamatergic inspiratory XII premotoneurons (preMNs) during sleep may contribute. Little is known about XII inspiratory preMNs due to their sparse distribution in the intermediate reticular formation (IRt). We hypothesized that ipsilaterally‐projecting XII inspiratory preMNs derive from Dbx1 progenitors, a transcription factor expressed in the IRt. Rhythmic, transverse medullary slices (550 μm) were produced from Dbx1 ERCreT2 ; R26 tdTomato neonatal mice (postnatal day 0‐5). Approximately 20% of the Dbx1 IRt neurons received inspiratory drive. In total we identified 29 inspiratory‐modulated Dbx1 IRt neurons via whole‐cell recording. 10 of 24 neurons were antidromically activated from the ipsilateral XII nucleus. Anatomical reconstruction of biocytin‐filled neurons revealed 10 commissural axons and 4 ipsilateral axons projecting to the XII nucleus. Using in situ hybridization, 57.3% (range 54.0‐58.9%) of Dbx1 IRt neurons were glutamatergic. Laser ablation of individual Dbx1 IRt neurons caused a significant (36 ± 3.6%) drop in ipsilateral, but not contralateral, XII inspiratory burst amplitude, and had no effect on inspiratory burst period. Thus, a subpopulation of Dbx1‐derived neurons in the IRt are XII inspiratory preMNs that contribute significantly to XII inspiratory output. This discovery will aid study of XII inspiratory preMNs. Funding: CIHR, NSERC, WCHRI, AIHS, CFI, NIH.