The Role of Nitric Oxide in Nonadrenergic Noncholingergic Neural Relaxation of Mammalian Airway Smooth Muscle

Abstract

Extensive evidence accumulated over the past two decades has documented the existence of an inhibitory nervous system in the airways of most mammalian species, including man, that is neither adrenergic nor cholinergic. Because the neurotransmitter of this system has not been identified with certainty, the system continues to be referred to as the nonadrenergic noncholinergic (NANC) inhibitory system. Most recently, attention has been focused on nitirc oxide (NO) as a possible transmitter of NANC inhibitory responses in the airways. This paper will succinctly review relevant background information regarding the airway NANC inhibitory system as well as current evidence advocating or disputing a role for NO in NANC inhibitory nerve-mediated relaxation of airway smooth muscle. Results from our own laboratory will be integrated with data reported by other investigators in an effort to present the reader with a balanced perspective on this intriguing, yet controversial topic.