Sympathetic and parasympathetic nervous control of airway resistance in dog lungs

We studied autonomic nervous control of central (Rc), peripheral (Rp), and extremely peripheral (Rep) airway resistances using a combination of a retrograde catheter method and a pleural capsule method. Airflow through the pleural capsule enabled us to measure Rep, which mainly reflected the resistance of local bronchioles less than 0.6 mm in diameter. Rp of the airways less than about 2 mm in diameter was not negligibly small at any lung volume (VL). With vagi intact, Rc increased at high as well as low VL, whereas Rp and Rep increased sharply as VL decreased. Vagal stimulation increased Rp more markedly than Rc, and Rep least of all. Propranolol augmented total airway resistance (Rtot) two to four times as much as vagal stimulation, mainly because of increased Rp. Stimulation of stellate ganglia inhibited up to half the increase of Rtot elicited by vagal stimulation; most of the inhibition occurred in Rp, but little in Rc and Rep. Our data suggest that both sympathetic and parasympathetic control is more extensive for Rp than for Rc or Rep.