Abstract: Aim To realize the regulatory actions of nitric oxide (NO) on supraoptic nucleus (SON) neurons by observing the effects of NO donor sodium nitroprusside (SNP) on SON neurons. Methods The cell electrophysioloical properties were obtained by the intracellular recording techniques from the SON neurons in adult rat hypothalamic slices. Results In 11 silent cells, superfusion of SNP(1 m mol·L^-1) for 3?5 min resulted in the depolarization response with a decrease of membrane resistance and time constant CP <0.05) in 55 % of cells while hyperpolarization with an increase of membrane resistance in 45% of neurons. In 73% of tested cells, SNP also decreased the amplitude, overshoot, firing frequency and slope of current voltage curve and increased the after hyperpolarization of action potentials evoked by intracellular depolarizing current pulses (P <3.05).However, SNP enhanced the spontaneous firing in 67% of 6 tested cells with spontaneous activities. Conclusion SNP presents an inhibitory or excitatory effect on SON neurons in a neuron type-and functional state-dependent manner, which suggests that NO may exhibit adverse regulatory actions on SON neurons.

Key words: sodium nitroprusside, supraoptic nucleus, nitric oxide, electrophysiology