Involvement of inhibitory innervation in reflex tracheal dilatation induced by lung inflation

We investigated the involvement of inhibitory innervation in reflex tracheal dilatation (RTD) induced by inflating the lungs in dogs. RTD was inhibited about 50% by 100 micrograms propranolol injected into the cranial thyroid artery, but was unaffected by adrenalectomy. Residual RTD under beta-blockade was abolished by sections of both the bilateral superior laryngeal nerves and spinal cord at the C1 level. These findings suggest that RTD may be mediated by adrenergic innervation and partly by nonadrenergic inhibitory innervation.