Sympathetic nerves innervate the airways of most species but their reflex regulation has been essentially unstudied. Here we demonstrate sympathetic nerve-mediated reflex relaxation of airway smooth muscle measured in situ in the @entity840 @entity825 . Retrograde tracing, immunohistochemistry and electrophysiological analysis identified a population of substance P-containing @entity2951 -sensitive spinal afferent neurones in the upper thoracic (T1-T4) dorsal root ganglia (DRG) that innervate the airways and lung. After bilateral vagotomy, @entity3897 pretreatment and pre-contraction of the trachealis with @entity112 , nebulized @entity2951 (10-60 microm) evoked a 63+/-7% reversal of the @entity112 -induced contraction of the trachealis. Either the beta-adrenoceptor antagonist @entity1169 (2 microm, administered directly to the @entity825 ) or bilateral sympathetic nerve denervation of the @entity825 essentially abolished these reflexes (10+/-9% and 6+/-4% relaxations, respectively), suggesting that they were mediated primarily, if not exclusively, by sympathetic adrenergic nerve activation. Cutting the upper thoracic dorsal roots carrying the central processes of airway spinal afferents also markedly blocked the relaxations (9+/-5% relaxation). Comparable inhibitory effects were observed following intravenous pretreatment with neurokinin receptor antagonists (3+/-7% relaxations). These reflexes were not accompanied by consistent changes in heart rate or blood pressure. By contrast, stimulating the rostral cut ends of the cervical vagus nerves also evoked a sympathetic adrenergic nerve-mediated relaxation that were accompanied by marked alterations in blood pressure. The results indicate that the @entity2951 -induced reflex-mediated relaxation of airway smooth muscle following vagotomy is mediated by sequential activation of @entity4756 -containing spinal afferent and sympathetic efferent nerves innervating airways. This sympathetic nerve-mediated response may serve to oppose airway contraction induced by parasympathetic nerve activation in the airways.

Reflex regulation of airway sympathetic nerves in XXXX .

@entity825 :: ('MESH:D055090', 'Disease') :: ['trachea'] @entity1169 :: ('MESH:D011433', 'Chemical') :: ['propranolol'] @entity2951 :: ('MESH:D002211', 'Chemical') :: ['capsaicin'] @entity840 :: ('10141', 'Species') :: ['guinea-pig'] @entity3897 :: ('MESH:D001285', 'Chemical') :: ['atropine'] @entity112 :: ('MESH:D006632', 'Chemical') :: ['histamine'] @entity4756 :: ('MESH:D015320', 'Chemical') :: ['tachykinin']
@entity840 :: (10141,Species) :: ['guinea-pigs']
