The pre-Botzinger complex is necessary for the expression of inspiratory and post-inspiratory motor discharge of the vagus

The mammalian three-phase respiratory motor pattern of inspiration, post-inspiration and expiration is expressed in spinal and cranial motor nerve discharge and is generated by a distributed ponto-medullary respiratory pattern generating network. Respiratory motor pattern generation depends on a rhythmogenic kernel located within the pre-B & ouml;tzinger complex (pre-B & ouml;tC). In the present study, we tested the effect of unilateral and bilateral inactivation of the pre-B & ouml;tC after local microinjection of the GABA(A) receptor agonist isoguvacine (10 mM, 50 nl) on phrenic (PNA), hypoglossal (HNA) and vagal nerve (VNA) respiratory motor activities in an in situ perfused brainstem preparation of rats. Bilateral inactivation of the pre-B & ouml;tC triggered cessation of phrenic (PNA), hypoglossal (HNA) and vagal (VNA) nerve activities for 15-20 min. Ipsilateral isoguvacine injections into the pre-B & ouml;tC triggered transient (6-8 min) cessation of inspiratory and post-inspiratory VNA (p < 0.001) and suppressed inspiratory HNA by - 70 +/- 15% (p < 0.01), while inspiratory PNA burst frequency increased by 46 +/- 30% (p < 0.01). Taken together, these observations confirm the role of the pre-B & ouml;tC as the rhythmogenic kernel of the mammalian respiratory network in situ and highlight a significant role for the pre-B & ouml;tC in the transmission of vagal inspiratory and post-inspiratory pre-motor drive to the nucleus ambiguus.