Water deprivation (WD) activates vasopressinergic neurons located in the hypothalamic supraoptic nucleus (SON) increasing the levels of vasopressin (VP) into the blood, which acts promoting vasoconstriction and urinary water retention. Previous studies have shown that neurons of SON express members of the cyclic nucleotide-gated family of ion channels like the hyperpolarization-activated and nucleotide-gated cation (HCN) channel that contribute to their electrical excitability and VP release. However, the contribution of hyperpolarization-activated inward current (IH) for excitatory drive of vasopressinergic SON neurons after WD have not been studied previously. Therefore, we will evaluate the role of IH in the control of electrical activity of vasopressinergic SON neurons after WD. Electrophysiological recordings will be performed through the patch-clamp technique using transgenic rats expressing enhanced green fluorescent protein (eGFP) under the control of VP promoter (VP-eGFP rats). Control (euhydrated) rats will have continuous access to water and food, whereas WD rats will have the water but not food removed for 48 h before initiating the experiments. The IH will be evaluated using the IH blocker ZD 7288.
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