Modulators of BK and SK Channels Alter Electrical Activity in Vitro in Single Vasopressin Neurons Isolated from the Rat Supraoptic Nucleus

Release of arginine vasopressin (AVP) from magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) is controlled by the electrical activities of the MNCs. Ca(2+)-activated K(+) channels, such as the BK and SK channels, are K(+)-selective ion channels that are activated in response to increased intracellular calcium concentrations. Intrinsic affinities for Ca(2+) permit these channels to exert a negative feedback effect on cellular excitability. In the present study, we used the whole-cell patch-clamp technique to examine the effects of BK or SK channel modulators on neuronal activity in single isolated rat SON MNCs that express an AVP-enhanced green fluorescent protein (eGFP) transgene. Application of BK or SK channel activators abolished the action potentials and induced hyperpolarization. In contrast, the number of action potentials was significantly increased after application of BK or SK channel blockers. Our results suggest that BK and SK channels in AVP neurons may play a role in the regulatory mechanisms of neural activity.