NITRIC-OXIDE AND CARBON-MONOXIDE - PARALLEL ROLES AS NEURAL MESSENGERS

Nitric oxide is now appreciated to be a molecule with important signal ing functions in the body, The purification and cloning of the first N O synthesizing enzyme, NO synthase (NOS), from brain has led to the ch aracterization of the roles of NO in normal physiology and in pathogen ic states. NO synthesis is regulated in a complex manner, involving th e association of activatory and inhibitory proteins. The body appears to use at least one other, highly related gas in a signaling function, carbon monoxide (CO). The enzyme responsible for CO biosynthesis in b rain, heme oxygenase-2 (HO2), is rapidly regulated by neurotransmitter stimulation. The role for CO as neurotransmitter is suggested by the altered intestinal motility in mice harboring a genomic deletion of HO 2. (C) 1998 Elsevier Science B.V. All rights reserved.