Reduction of depolarization-induced glutamate release by heme oxygenase inhibitor: possible role of carbon monoxide in synaptic transmission.

The effects of carbon monoxide on the release of glutamate were studied in synaptoneurosomal preparations using a fluorometric system. Zinc protoporphyrin IX, an inhibitor of the heme oxygenase that produces carbon monoxide, reduced depolarization-induced glutamate release in a calcium-dependent manner, but had no effect on calcium-independent glutamate release. On the basis of this finding, we suggest that carbon monoxide plays a pivotal role in glutamate release in synapses, and may be a retrograde messenger in long-term potentiation.