The effects of noradrenaline (NA) and its analogues on subfornical organ (SFO) neurons in rat slice preparations were investigated by using whole cell patch clamp recording. In the current-clamp mode, the application of NA at 10-100 µM produced membrane depolarization (63%, 17 responsive neurons /27 neurons tested) and hyperpolarization (22%, 6/27 neurons). In the voltage-clamp mode, NA application at 1-100 µM produced inward currents (69%, 42/61 neurons) and outward currents (23%, 14/61 neurons). These currents were remained in the presence of TTX or both glutamate and GABA receptor antagonists. In most of the neurons (25/31 neurons) showing inward currents in the presence of NA, the membrane conductance was not changed by voltage ramps or hyperpolarizing pulse stimulation. Similar responses were obtained by the application of the 1 agonist phenylephrine. The phenylephrine-induced inward currents were inhibited by the 1 antagonist prazosin. The 2 agonist clonidine decreased the frequency of spontaneous GABAergic inhibitory postsynaptic currents (4/10 neurons). In addition, RT-PCR assay and immunohistochemical staining showed existence of 1 adrenoceptors in the SFO. The results suggest that SFO neurons in rats are activated postsynaptically through 1 adrenoceptors, and that the activation is enhanced by suppressing GABAergic inhibitory synaptic inputs through presynaptic 2 adrenoceptors.