DUAL EFFECT OF SODIUM-NITROPRUSSIDE ON POTENTIALS RECORDED FROM MOUSEHIPPOCAMPAL SLICES

The purpose of this research was to estimate the usefulness of sodium nitroprusside (SNP) as a donor of nitric oxide (NO) in the study of sy naptic plasticity. The influence of SNP, K3Fe(CN)(6) and K4Fe(CN)(6) o n the evoked potential recorded from mouse hippocampal slices was eval uated. When slices were exposed to 1 mM SNP for no longer than 15 min, a facilitation of the population spike was observed following perfusi on. Longer, 60 min exposure of the slices to 1 mM SNP prevented this p erfusion-induced amplification of the potential and blocked the induct ion of LTP by subsequently applied high frequency stimulation (HFS). S NP at lower concentrations (0.2 mM) had no effect. SNP (1 mM) suppress ed the NMDA component of the population spike. Light inactivated, 1.0 mM SNP, when applied for 15 min, reduced the potential and subsequentl y induced LTP. However, longer exposure of the slices to the light ina ctivated 1 mM SNP made the potential unstable and blocked induction of LTP. K3Fe(CN)(6) and K4Fe(CN)(6) molecules structurally related to SN P but unable to generate NO, transiently amplified the population spik e and its NMDA component. We suggest that SNP, which is often used as nitric oxide donor, exerts a dual inhibitory and facilitatory action o n hippocampal evoked potentials. The possible mechanisms of these acti ons are discussed.