Muscarinic receptor-mediated activation of nitric oxide synthase

The potent vasodilator factor released from endothelial cells upon activation of muscarinic acetylcholine receptors has recently been identified as nitric oxide (NO). This discovery has sparked intensive research efforts aiming at understanding the functional role of this short-lived, highly reactive free radical. As a result, it has been shown that NO is a very important second messenger involved in a wide spectrum of physiological functions. One important aspect that differentiates NO from other second messengers is that NO is a 'traveling' messenger that diffuses out of the cells of its origin to produce marked effects in neighboring cells. This paper provides a synopsis of the diverse biological roles of NO and the mechanisms of its generation upon activation of muscarinic acetylcholine receptors.