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This Article Full Text Full Text (PDF) All Versions of this Article: 297/3/R699    most recent 00041.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Minoura, Y. Articles by Kobayashi, Y. PubMed PubMed Citation Articles by Minoura, Y. Articles by Kobayashi, Y.

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Electrophysiological responses of sympathetic preganglionic neurons to ANG II and aldosterone

Departments of ¹Medicine Division of Cardiology and ²Physiology, Showa University School of Medicine, Tokyo Japan; and ³Department of Internal Medicine, Keio University School of Medicine, Tokyo Japan

Submitted 16 January 2009 ; accepted in final form 11 June 2009

The intermediolateral cell column (IML) of the spinal cord is an important area where sympathetic impulses propagate to peripheral sympathetic organs. ANG II and aldosterone are important components of the renin-angiotensin-aldosterone system (RAAS), which activate the sympathetic nervous system. Each is partly synthesized in the brain and plays a paracrine role in the regulation of blood pressure independently of RAAS in the periphery. Our purpose in the present study was to clarify the contributions of sympathetic preganglionic neurons in the IML (IML neurons) and the effects of ANG II and aldosterone on the sympathetic nervous system. To examine responses to ANG II and aldosterone, we intracellularly recorded 104 IML neurons using a whole cell patch-clamp technique in spinal cord slice preparations. IML neurons were classified into two types: silent and firing. Both neuron types were significantly depolarized by ANG II, and candesartan inhibited this depolarization. After pretreatment with TTX, firing neurons (but not silent neurons) were significantly depolarized by ANG II. Aldosterone significantly increased the number of excitatory postsynaptic potentials (EPSPs) in both neuron types, but this response disappeared after pretreatment with TTX. ANG II and aldosterone had no synergistic effects on the IML neurons. The silent neurons had large cell soma, and many more dendrites than the firing neurons. These results suggest that ANG II acts presynaptically and postsynaptically in IML neurons, while aldosterone acts mainly presynaptically. Thus, the physiological effects of these substances are likely to be transmitted via specific membrane receptors of IML and/or presynaptic neurons.

sympathetic preganglionic neuron; intermediolateral cell column