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This Article Full Text Full Text (PDF) All Versions of this Article: 101/4/2134    most recent 91030.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map 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 Google Scholar Google Scholar Articles by Marchenko, V. Articles by Rogers, R. F. Search for Related Content PubMed PubMed Citation Articles by Marchenko, V. Articles by Rogers, R. F.

GABA_Aergic and Glycinergic Inhibition in the Phrenic Nucleus Organizes and Couples Fast Oscillations in Motor Output

Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware

Submitted 15 September 2008; accepted in final form 10 February 2009

One of the characteristics of respiratory motor output is the presence of fast synchronous oscillations, at rates far exceeding the basic breathing rhythm, within a given functional population. However, the mechanisms responsible for organizing phrenic output into two dominant bands in vivo, medium (MFO)- and high (HFO)-frequency oscillations, have yet to be elucidated. We hypothesize that GABA_Aergic and glycinergic inhibition within the phrenic motor nucleus underlies the specific organization of these oscillations. To test this, the phrenic nuclei (C₄) of 14 unanesthetized, decerebrate adult male Sprague-Dawley rats were microinjected unilaterally with either 4 mM strychnine (n = 7) or GABAzine (n = 7) to block glycine or GABA_A receptors, respectively. Application of GABAzine caused an increase in overall phrenic amplitude during all three phases of respiration (inspiration, postinspiration, and expiration), while the increases caused by strychnine were most pronounced during postinspiration. Neither antagonist produced changes in inspiratory duration or respiratory rate. Power spectral analysis of inspiratory phrenic bursts showed that blockade of inhibition caused significant reduction in the relative power of MFO (GABA_A and glycine receptors) and HFO (GABA_A receptors only). In addition, analysis of the coherence between the firing of the ipsi- and contralateral phrenic nerves revealed that HFO coupling was significantly reduced by both antagonists and that of MFO was significantly reduced only by strychnine. We conclude that both GABA_A and glycine receptors play critical roles in the organization of fast oscillations into MFO and HFO bands in the phrenic nerve, as well as in their bilateral coupling.