NANC responses — role in control of airway tone

Abstract

Since the first reports on neurally mediated nonadrenergic, non-cholinergic (NANC) contractile and relaxant smooth-muscle responses in mammalian airways, impressive efforts have been made in order to characterize these NANC responses in vitro and in vivo (l-l 1). There is now evidence that both types of NANC responses are present not only in the airways of lower mammals but also in the airways of primates, including man (7,9,12-16). In spite of the large number of studies on NANC responses, however, little is known about the role of these neurally mediated smooth-muscle responses in the control of airway smooth-muscle tone. The present review therefore focuses on the main findings in a series of recently performed studies evaluating the functional role of NANC responses in the control of airway smooth-muscle tone. The main aims of the reviewed studies were to characterize the relationship between the level of airway smooth-muscle tone prior to NANC activation, the basal tone, and the direction and magnitude of the NANC neural response as well as the influence of simultaneous adrenergic and cholinergic activation on this relationship.