Key result
The authors argue that while some physiological variables can be studied in humans, complex mechanisms like baroreceptor reflexes and vascular capacitance often require animal models to control confounding variables.
Design
Editorial
The authors argue that while some physiological variables can be studied in humans, complex mechanisms like baroreceptor reflexes and vascular capacitance often require animal models to control confounding variables.
LETTERS TO THE EDITORCommentary on Viewpoint “Human experimentation: No accurate, quantitative data?”R. Hainsworth, and M. J. DrinkhillR. Hainsworth, and M. J. DrinkhillPublished Online:01 Mar 2007https://doi.org/10.1152/japplphysiol.01360.2006MoreSectionsPDF (25 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations To the Editor: We entirely agree with Rowell (Ref. 5, this issue) that many physiological variables can indeed be studied accurately and quantitatively in humans. However, for the study of mechanisms, particularly where complex preparations are needed to control confounding variables, it is often necessary to resort to the use of experimental animals. We give examples to illustrate this.Baroreceptor reflexes can be studied in humans by intravenous injections of vasoactive substances or by applying pressures to the carotid regions. While this gives useful information, it fails adequately to describe the reflex, because, in the “open loop” situation, any response would quickly be altered (“buffered”) by other reflexes affected by the stimulus, the response, or both. In animals, both the reflexogenic area and the effector organs can be isolated, thereby avoiding this problem (2).We described, in anesthetized dogs, a powerful baroreceptor reflex from the coronary arteries (6). The complex experimental preparation necessitated isolating the stimulus site and other reflexogenic areas. All this is clearly impossible in people, but we have shown in humans undergoing cardiac surgery that the reflex does exist, at least qualitatively, but certainly not accurately or quantitatively (3).Rowell referred to our Counterpoint article on vascular capacitance. Capacitance is the volume of blood (in a region) at constant distending pressure (1). Both arterial inflow and venous pressure must be controlled or passive volume changes would occur (4). Responses in humans, at present therefore, must be inferred from animal data, taking into account known species differences such as the absence of a large contractile spleen in people.REFERENCES1 Hainsworth R. Vascular capacitance: its control and importance. Rev Physiol Biochem Pharmacol 105: 101–173, 1986.Crossref | PubMed | ISI | Google Scholar2 Hainsworth R, Karim F. Responses of abdominal vascular capacitance in the anaesthetized dog to changes in carotid sinus pressure. J Physiol 262: 659–677, 1976.Crossref | ISI | Google Scholar3 Kincaid K, Ward M, Nair U, Hainsworth R, Drinkhill M. The coronary baroreflex in humans. J Extra Corpor Technol 37: 306–310, 2005.Google Scholar4 Noble BJ, Drinkhill MJ, Myers DS, Hainsworth R. Reflex control of splanchnic blood volume in anaesthetized dogs. J Physiol 513: 263–272, 1998.Crossref | PubMed | ISI | Google Scholar5 Rowell L. Human experimentation: No accurate, quantitative data? J Appl Physiol. In press.Google Scholar6 Wright C, Drinkhill MJ, Hainsworth R. Reflex effects of independent stimulation of coronary and left ventricular mechanoreceptors in anaesthetized dogs. J Physiol 528: 349–358, 2000.Crossref | PubMed | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: R. Hainsworth, Institute for Cardiovascular Research, Univ. of Leeds, Leeds LS2 9JT, UK (e-mail: [email protected]) Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 102Issue 3March 2007Pages 1293-1293 Copyright & PermissionsCopyright © 2007 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.01360.2006PubMed17341742History Published online 1 March 2007 Published in print 1 March 2007 Metrics
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Hainsworth et al. (2007) reported a letter. The authors argue that while some physiological variables can be studied in humans, complex mechanisms like baroreceptor reflexes and vascular capacitance often require animal models to control confounding variables.
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