Neural elements subserving pulmonary stretch receptor-mediated facilitation of phrenic motoneurons.

The neural elements responsible for facilitation of phrenic nerve activity by lung inflation were investigated in cats by the simultaneous recording of individual pulmonary stretch receptor afferents, respiratory neurons of the ventrolateral nucleus of the tractus solitarius and phrenic nerve activity. Monosynaptic excitation of I beta neurons by slowly adapting pulmonary stretch receptors was demonstrated by cross-correlational analysis. It was also demonstrated that the majority of these same I beta neurons projected to the contralateral C5 phrenic motoneuron pool. Thus, this study has shown that I beta neurons can act as central neural elements to mediate the facilitatory effect of lung inflation upon phrenic nerve activity.