The effect of sodium nitroprusside on resting membrane potential of the leech Retzius nerve cells

We have investigated the effect of sodium nitroprusside (SNP) on the membrane resting potential of the leech (Haemopis sanguisuga) Retzius nerve cells (RNC). The membrane potential of RNC of isolated ganglia was recorded in Ringer solution, in SNP solution during the next 30 minutes and after washing out with Ringer solution. We used 1 mmol/L, 2 mmol/L and 5 mmol/L solutions of SNP. Kruskal-Wallis ANOVA test was used to compare the fall of membrane potential of the leech Retzius nerve cells when different SNP concentrations were used. There was no change in the membrane resting potential of the leech Retzius nerve cells with 1 mmol/L concentration of SNP whilst 2 mmol/L concentration of SNP induced hyperpolarization during the first 20 minutes. The highest concentration of 5 mmol/L SNP induced hyperpolarization in 50% of cells during the first minute and during the next 10 minutes in the other 50%. The significant fall of membrane potential was recorded with 5mmol/L SNP concentration (p<0.05). The SNP induced hyperpolarization of RNC might be the effect of this NO donor on the potassium channels of leech RNC