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This Article Full Text Full Text (PDF) All Versions of this Article: 579/2/515    most recent jphysiol.2006.121889v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Chamberlin, N. L. Articles by Malhotra, A. Search for Related Content PubMed PubMed Citation Articles by Chamberlin, N. L. Articles by Malhotra, A. Related Collections Respiratory

¹ Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA
² Divisions of Sleep Medicine and Pulmonary/Critical Care Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, 02115 USA

Reflex increases in genioglossus (GG) muscle activity in response to negative pharyngeal pressure are important for maintenance of upper airway patency in humans. However, little is known of the central circuitry that mediates this negative pressure reflex (NPR). We used two approaches to determine which GG premotoneurons relay negative pressure-related information to the hypoglossal motor nucleus. First, to identify GG premotoneurons, we injected pseudorabies virus (PRV152) into the GG muscle. We found that medullary GG premotoneurons were concentrated mainly in the reticular formation adjacent to the hypoglossal motor nucleus. Second, in order to determine whether these perihypoglossal neurons were involved in the NPR, we quantified GG EMG responses to negative pressure applied to the isolated upper airway in anaesthetized rats before and after microinjection of muscimol (9 nl; 0.25 mM), a GABA-A receptor agonist, into the perihypoglossal premotor field. Pressures as low as –4 cmH₂O increased inspiratory phase-related GG activity. The NPR was abolished following bilateral injections of muscimol into the perihypoglossal premotor field at and up to 500 µm rostral to the obex. Muscimol in this location also increased the amplitude of basal, unstimulated phasic GG activity. By contrast, inhibition of neurons caudal to the obex decreased phasic GG activity but had no impact on the NPR. These results suggest that perihypoglossal GG premotoneurons near the obex mediate the NPR and those caudal to the obex are important mediators of respiratory-related GG activity but are not involved in the NPR.

(Received 27 September 2006; accepted after revision 20 December 2006; first published online 21 December 2006)
Corresponding author N. L. Chamberlin: Department of Neurology, Beth Israel Deaconess Medical Center, 77 Ave. Louis Pasteur, Boston, MA 02115, USA.  Email: nchamber{at}bidmc.harvard.edu

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