Carbon Monoxide: a Putative Neural Messenger

TLDR

Carbon monoxide, produced by heme oxygenase, activates guanylyl cyclase. Neuronal localization of heme oxygenase mRNA, mirroring soluble guanylyl cyclase, together with inhibition studies showing reduced cGMP, indicates that carbon monoxide may act as a neurotransmitter regulating cGMP.

Abstract

Carbon monoxide, an activator of guanylyl cyclase, is formed by the action of the enzyme heme oxygenase. By in situ hybridization in brain slices, discrete neuronal localization of messenger RNA for the constitutive form of heme oxygenase throughout the brain has been demonstrated. This localization is essentially the same as that for soluble guanylyl cyclase messenger RNA. In primary cultures of olfactory neurons, zinc protoporphyrin-9, a potent selective inhibitor of heme oxygenase, depletes endogenous guanosine 3′,5′-monophosphate (cGMP). Thus, carbon monoxide, like nitric oxide, may be a physiologic regulator of cGMP. These findings, together with the neuronal localizations of heme oxygenase, suggest that carbon monoxide may function as a neurotransmitter.