Serotonin hyperpolarizes the dorsal raphe nucleus neurons of mice by activating G protein-coupled inward rectifier potassium channels

Serotonin (5-HT) has an important role in the pathophysiology of the mood disorders like major depression and anxiety disorders in central nervous system. On the one hand, dorsal raphe nucleus (DRN) neurons send serotonergic projections to almost all brain regions. On the other hand, they affect themselves through 5-HT1A autoreceptors. Many electrophysiological studies have investigated the ionic mechanism of the 5-HTs effect on the DRN neurons of the rat. However, there is no study characterizing the current that mediates the 5-HTs effect on mouse DRN neurons. In the present electrophysiological study, the whole-cell patch-clamp technique was used in the neurons of the DRN from one-month-old Balb/c mice to investigate the effect of 5-HT on the DRN neurons of mice and its ionic mechanism of action. The application of 5-HT resulted in a 14.3 +/- 3.1 mV hyperpolarization (n= 9,P< 0.01) of resting membrane potential and 25.7 +/- 3.5 pA outward current (n= 7) in the DRN neurons. The reversal potential (E5-HT) of the current induced by 5-HT was close to the potassium equilibrium potential (E-K). This current had an inward rectification feature and was blocked by quinine pretreatment (n= 5,P< 0.05). In conclusion, 5-HT inhibits the DRN neurons of mice by inducing a current that is carried by potassium ions through G-protein-coupled inward rectifier potassium channels.