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Am J Physiol Regul Integr Comp Physiol 290: R1646-R1653, 2006. First published February 2, 2006; doi:10.1152/ajpregu.00801.2004
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NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Activation of subfornical organ neurons in rats through pre- and postsynaptic {alpha}-adrenoceptors

Eiko Honda, Kentaro Ono, Shinji Kataoka, and Kiyotoshi Inenaga

Department of Biosciences, Kyushu Dental College, Kokurakitaku, Kitakyushu, Japan

Submitted 29 November 2004 ; accepted in final form 26 January 2006

The effects of noradrenaline (NA) and its analogs 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 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 {alpha}1-agonist phenylephrine. The phenylephrine-induced inward currents were inhibited by the {alpha}1-antagonist prazosin. The {alpha}2-agonist clonidine decreased the frequency of spontaneous GABAergic inhibitory postsynaptic currents (4/10 neurons). In addition, RT-PCR assay and immunohistochemical staining showed the existence of {alpha}1-adrenoceptors in the SFO. The results suggest that SFO neurons in rats are activated postsynaptically through {alpha}1-adrenoceptors and that the activation is enhanced by suppressing GABAergic inhibitory synaptic inputs through presynaptic {alpha}2-adrenoceptors.

patch clamp; slice preparation; noradrenaline


Address for reprint requests and other correspondence: K. Inenaga, Dept. of Biosciences, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu 803-8580 Japan (E-mail: ine{at}kyu-dent.ac.jp)






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