The use of NO-sensitive microelectrodes for direct detection of nitric oxide (NO) production in molluscs.

The endogenous production of nitric oxide (NO) from the CNS and a peripheral sensory structure (osphradium) of the pulmonate molluscs, Lymnaea stagnalis and Limax sp. as well as from the rat aorta was studied using two different types of NO-sensitive microelectrodes. Both NO-sensitive electrodes gave complementary, but comparable results. From our data it was possible to compile a hierarchy of tissues with respect to estimated NO production: the rat aorta (300-600 nM) > Lymnaea osphradium (100-300 nM) > Lymnaea buccal ganglia (30-100 nM) > Limax protocerebrum (10-50 nM). In the preparations tested the administration of L-arginine (10 nM) caused an increased level of the recorded signals. This effect was suppressed by NG-Nitro-L-arginine (10 nM), an inhibitor of NOS. It may be concluded that NO can be detected directly from the CNS and peripheral tissues of Lymnaea, and rat aorta, despite the limitations of the techniques used. The putative level of NO production in the osphradium is higher than that in areas of the mammalian CNS and can be compared with release from the aorta. The NO release from the buccal ganglia and the protocerebrum was comparable with that of the rat cerebellum. Such high levels of NO production lend themselves to further analysis of the biological role of this molecule in molluscs.