NO-SYNTHASE - WHAT CAN RESEARCH ON INVERTEBRATES ADD TO WHAT IS ALREADY KNOWN

The present study attempts to review presently known data regarding th e distribution of nitric oxide (NO) synthase and the function of NO in invertebrate species. NO is synthesized from L-arginine by the enzyme NO synthase, and activates guanylate cyclase which in turn leads to a n increase in levels of cGMP in target cells. Major contributions to t he knowledge of NO as a messenger molecule in invertebrates have been made by NADPH-diaphorase histochemistry and biochemical assays. These techniques suggest the presence of a L-arginine/NO pathway in a variet y of tissues, thus implicating muliple roles for NO in invertebrates.