Evidence that the preBotzinger complex does not participate in cough rhythmogenesis in the anesthetized cat.

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The nucleus tractus solitarius (NTS) participates in cough phase timing in the anesthetized cat. The preBotzinger complex (preBotC) is key for breathing rhythmogenesis, but the role of this area in regulating cough rhythmogenesis is still unknown. We hypothesized that excitation of neurons in the preBotC would modulate shorten the duration of the inspiratory cough, consistent with the effects during breathing. To test this hypothesis, we unilaterally microinjected 5 mM DL‐Homocysteic acid (DLH) into the preBotC in anesthetized, spontaneously breathing adult cats (n=7). In 3 of these animals, 15 mM DLH also was injected into the preBotC. Criteria for data inclusion were multi‐unit inspiratory neuron recording at the injection site, apneusis or tachypnea as a result of DLH injection, and histological verification of the injection site. We recorded esophageal pressure (EsPr) and electromygrams (EMG) from inspiratory (parasternal and diaphragm) and expiratory (internal oblique) muscles. Tracheobronchial cough was induced via mechanical stimulation of the intrathoracic trachea. DLH microinjection significantly altered the breathing response: breathing frequency increased (18.0±1.4 to 46.9±7.4 bpm) due to changes in both inspiratory time (TI − 1.04±0.5 to 0.75±0.76 s) and expiratory time (TE −2.34±0.19 to 0.63±0.16 s). Diaphragm EMG magnitude did not change significantly. Microinjection of DLH (5 mM) into the preBotC did not alter cough phase timing (cough frequency: 23.3±4.0 to 22.9±4.4 coughs per minute; TI − 1.27±0.13 to 1.31±0.10 s; TE1 −0.26±0.7 to 0.26±0.07 s; TE2 − 1.35±0.24 to 1.29±0.49 s). While the magnitude of cough pressures and diaphragm EMGs were not altered (EsPr – control 49.4±5.8 to DLH 35.7±5.2 ; EMG amplitude ‐ control 70.8±3.5 to DLH 65.1±6.5), cough expiratory motor drive was significantly lower (abdominal – control 62.1±5.5 to DLH 40.0±5.9%, p <0.04). Microinjections of 15 mM DLH into the preBotC eliminated cough. In the 3 animals that had both 5 and 15 mM DLH injections, there was a trend for a longer recovery time for cough with the higher concentration of DLH (5 mM – 33.8±10.4 s; 15 mM – 66.8±27.5 s). Unlike for breathing, excitation of neurons via DLH in the region of the preBotC does not affect phase timing for cough, although DLH appears to exhibit a dose‐dependent cough suppression.Support or Funding InformationSupported by NIH HL 103415 and 1OT20D001983.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.