Circuits in the Ventral Medulla That Phase-Lock Motoneurons for Coordinated Sniffing and Whisking

Figure 3

Facial motoneurons and sniffing. (a, b) Recording of facial motoneurons in alert head-restrained rats reveals respiration-related cells that fire preferentially during sniffing. (c) Electromyographic recording of NLP motor units during basal respiration and sniffing. Note that the small unit is active during both basal respiration and sniffing, while the large unit only fires during sniffing. (d) Raster plots of the activity of NLP motor units relative to the onset of inspiration (black lines). Black and red dots represent spikes of the small and large motor units shown in (c), respectively. Individual breaths are ordered by the duration of the breath. The green line indicates the transition between basal respiration and sniffing. Note that the small unit is active during inspiration at all breathing frequencies, while the large unit is preferentially active during sniffing. (e) Sindbis-GFP injection in the retrofacial region leads to anterograde labeling in the facial nucleus. (f) Confocal microscopy reveals a majority of labeled boutons that are immunopositive for type 2 vesicular glutamate transporter (VGluT2). Framed areas A and B are enlarged in the corresponding inserts. (g) Example of respiration-related neurons of the retrofacial region that are principally recruited during sniffing. Data in panels (a) to (d) are adapted from [20], while data in panels (e) to (g) are unpublished results.

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