Nitric Oxide Physiology and Pharmacology

Stephen M. Stahl, M.D., Ph.D.

Issue: Nitric oxide gas (NO) is an unconventional neurotransmitter that is synthesized upon demand. In the brain, it may allow postsynaptic elements to talk back to presynaptic neurons. In peripheral tissues it mediates smooth muscle relaxation. Various pharmacologic agents can enhance or reduce the actions of NO. (J Clin Psychiatry 1998;59:101-102)

Figure 1
During neurotransmission in the brain, some postsynaptic elements form nitric oxide gas (NO) in response to nerve stimulation. The enzyme nitric oxide synthase (NOS) synthesizes NO1-4 by converting the amino acid arginine into both NO and the by-product citrulline. This free NO is then able to diffuse ("talk back") to the presynaptic neuron, which could be how 2-way communication between presynaptic and postsynaptic elements occurs in some CNS synapses.

Brainstorms aims to provide updates of novel concepts emerging from the neurosciences that have relevance to practitioners.

From the Clinical Neuroscience Research Center in San Diego and the Department of Psychiatry at the University of california San Diego.