Effects of hydrogen peroxide and nitric oxide (NO) on neuronal discharges and intracellular calcium concentration in the molluscan CNS

Abstract

In the isolated brain of the freshwater pulmonate snail, Lymnaea stagnalis, application of H2O2 (0.003-0.0003%) activated specific discharge patterns both in neurones of the respiratory and feeding networks, as well as in other identified central neurones and these observed effects were different from the effects of NO or NO-donors. At least part of these effects could be mediated by changes in intracellular calcium concentration, [Ca2+]i, because both the NO-donor, sodium nitroprusside (10(-6)-10(-4) M) and H2O2 (0.003-0.0003%) increased [Ca2+]i in a concentration-dependent manner in isolated neurones in culture. The level of increased [Ca2+]i depended on the drug tested and was characteristic of the identified neurone investigated. We suggest that both NO and H2O2 may be functionally different components of the same neuronal signalling system associated with NO synthase or related enzyme(s).