9458100 Bredt Nitric oxide (NO) is a noxious free radical gas which, remarkably, functions as an endogenous biological messenger molecule. Initially identified in mammalian macrophages and endothelial cells, NO appears to have prominent influences in diverse tissues throughout the animal kingdom. NO represents a major divergence from previously characterized cellular signals. While other transmitters reversibly interact with high affinity receptors in a "lock-and-key" manner, NO achieves signaling specificity not by its three dimensional shape but rather by its radical chemical reactivity. Under ambient conditions NO is a lipophilic gas; these properties allow it to rapidly diffuse into cells without being restrained by cellular barriers. The discovery of NO as a messenger has prompted a search for other small reactive biological mediators and already several have been found in organisms ranging from bacteria to primates. This laboratory is using molecular and genetic approaches to define the roles of NO in the functioning and development of the nervous system. Owing to its reactive free-radical structure, experimentally adding NO to a biological system may cause non-specific effects which are physiologically unimportant. Also, NO is technically difficult to deliver in a manner which resembles endogenous synthesis. To avoid these problems these studies will make use of transgenic NOS "knockout" mice generated by targeted disruption of the endogenous gene. These animals are viable and furtile and should serve as an excellent model to study the neuronal functions for NO. The PI will also develop a "dominant negative" genetic approach to delete NOS from specific cell types and during selected stages of development. These and other future studies of NO may help serve as a model for understanding signaling by other members of this new class of biological messengers.
