AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 1 34-R41, Copyright © 1996 by American Physiological Society

ARTICLES

Subcellular mechanisms of angiotensin II and arginine vasopressin activation of area postrema neurons

F. M. Consolim-Colombo, M. Hay, T. C. Smith, M. Elizondo-Fournier and V. S. Bishop
Department of Physiology, University of Texas Health Science Center at San Antonio 78284-7756, USA.

Angiotensin II (ANG II) and arginine vasopressin (AVP) act on area postrema (AP) neurons to modulate the baroreflex. Because activation of AP neurons by either ANG II or AVP increases intracellular free Ca2+ concentrations ([Ca2+]i), the goal of this study was to analyze the factors affecting the [Ca2+]i responses to ANG II and AVP. Neurons were recovered from 14- to 16-day old rats and studied after 8-14 days in culture by use of the microscopic digital image analysis for fura 2-loaded cells. The effects of ANG II (100 nM) and AVP (100 nM) on [Ca2+]i were determined in normal (2 mM) and low (< 10 nM) extracellular Ca2+ concentrations. In 143 of 240 neurons, ANG II increased [Ca2+]i 4.65-fold after 20 s, and a similar response was observed in the absence of extracellular Ca2+ (3.65-fold after 20 s). After 60 s of observation, steady-state levels of increased [Ca2+]i were still present under both conditions. Pretreatment with AT1 antagonist or pertussis toxin abolished the response to ANG II. AVP also increased [Ca2+]i (3.6-fold at peak, 20 s) in normal and low extracellular Ca2+. Pretreatment with AVP V1 antagonist or pertussis toxin abolished the response to AVP. This study indicates that ANG II-induced increases in [Ca2+]i are independent of extracellular Ca2+ concentrations and involve the activation of AT1 receptors and a pertussis toxin-sensitive G protein. Although AVP affects a fewer number of AP neurons, the mechanisms of activation are also independent of extracellular Ca2+ concentration and are mediated by a pertussis toxin-sensitive G protein.

This article has been cited by other articles:

				Q. Chen and H.-L. Pan Signaling Mechanisms of Angiotensin II-Induced Attenuation of GABAergic Input to Hypothalamic Presympathetic Neurons J Neurophysiol, May 1, 2007; 97(5): 3279 - 3287. [Abstract] [Full Text] [PDF]

				J. Pamidimukkala and M. Hay 17{beta}-Estradiol inhibits angiotensin II activation of area postrema neurons Am J Physiol Heart Circ Physiol, October 1, 2003; 285(4): H1515 - H1520. [Abstract] [Full Text] [PDF]

				B. Xue, H. Gole, J. Pamidimukkala, and M. Hay Role of the area postrema in angiotensin II modulation of baroreflex control of heart rate in conscious mice Am J Physiol Heart Circ Physiol, March 1, 2003; 284(3): H1003 - H1007. [Abstract] [Full Text] [PDF]

				M. Hay and K. A. Lindsley AMPA receptor activation of area postrema neurons Am J Physiol Regulatory Integrative Comp Physiol, February 1, 1999; 276(2): R586 - R590. [Abstract] [Full Text] [PDF]

				X. Ma, M. W. Chapleau, C. A. Whiteis, F. M. Abboud, and K. Bielefeldt Angiotensin Selectively Activates a Subpopulation of Postganglionic Sympathetic Neurons in Mice Circ. Res., April 27, 2001; 88(8): 787 - 793. [Abstract] [Full Text] [PDF]