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¹ Department of Physiology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan

It is recognized that brain contains all the components of the renin–angiotensin systems (RAS). The nucleus of the tractus solitarius (NTS) is known to play a major role in the regulation of cardiovascular, respiratory, gustatory, hepatic and swallowing functions. Voltage-dependent Ca²⁺ channels (VDCCs) serve as crucial mediators of membrane excitability and Ca²⁺-dependent functions such as neurotransmitter release, enzyme activity and gene expression. The purpose of this study was to investigate the effects of angiotensin II (Ang II) on VDCC currents (I_Ca) in the NTS using patch-clamp recording methods. An application of Ang II caused facilitation of L-type I_Ca in a concentration-dependent manner with an EC₅₀ of 167 nM and a Hill coefficient of 1.73. AT₁ receptor antagonist losartan antagonized the Ang II-induced facilitation of I_Ca. Intracellular dialysis of the G_i-protein antibody attenuated the Ang II-induced facilitation of I_Ca. Both Src tyrosine kinase inhibitor and mitogen-activated protein kinase (MAPK) inhibitor attenuated the Ang II-induced facilitation of I_Ca. p38 MAPK inhibitor also attenuated the Ang II-induced facilitation of I_Ca. These results indicate that Ang II facilitates L-type VDCCs via G_i-proteins involving Src tyrosine kinase and p38 MAPK kinase mediated by AT₁ receptors in NTS.

(Received 25 July 2005; accepted after revision 23 August 2005; first published online 25 August 2005)
Corresponding author T. Endoh: Department of Physiology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan. Email: tendoh{at}tdc.ac.jp

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