Baroreceptor function and changes in strain sensitivity in normotensive and spontaneously hypertensive rats.
Year: 1980
Type: article
Abstract: Baroreceptor resetting during hypertension has been attributed to a reduction in the distensibility of the vessel wall in which the receptors are located.According to this hypothesis, a simple increase in pressure is all that is required to overcome the increase in vessel wall stiffness.However, previous work from our laboratory suggested a more complicated situation.Measurements of both vessel wall mechanical properties and baroreceptor discharge characteristics in spontaneously hypertensive rats (SHR) showed that distortion thresholds for the receptors also undergo changes.Here we have examined the time course of resetting, measuring both aortic distensibility and baroreceptor properties in SHR and mormotensive Wistar-Kyoto rats (WKY) from 5 to 30 weeks in age.An in vitro aortic arch-aortic nerve preparation was used.We found that for a given pressure the aortic radii of WKY were increasing much more rapidly than the aortic radii for SHR and, beyond 5 weeks of age, were much more distensible.The lower distensibility in SHR was accompanied by increased wall thickness.The discharge characteristics of single baroreceptors were expressed in terms of both pressure and distortion or circumferential wall strain.The change in distensibility of WKY aortas from 5 to 30 weeks was suitably matched by an increase in the strain threshold for discharge of WKY baroreceptors resulting in a constant pressure threshold for discharge.The lower distensibility of SHR aortas was accompanied by lower threshold strains in SHR baroreceptors, but the changes were not suitably matched, and progressive resetting of SHR baroreceptors to higher threshold pressures occurred.The two sets of receptors appear to be different as early as 5 weeks of age when blood pressures are similar and, futhermore, these differences are accentuated by age and hypertension.CircRes 47: 821-828, 1980 ARTERIAL baroreceptor function is abnormal in all forms of established hypertension; greater distending pressures are required to activate the receptors, and the suprathreshold sensitivity to pressure changes is reduced (McCubbin et al., 1956).Since distensibility of the vessel wall in which the receptors are located is reduced at this time, the resetting of baroreceptor function to higher operating pressures has been attributed to the confinement or "splinting" of receptors within a stiffer vessel (Angell-James, 1973;Nosaka and Wang, 1972;Sapru and Wang, 1976; Kedzi, 1976;Jones, 1977).Investigations of the time course of baroreflex resetting during experimental renal hypertension indicate that the threshold pressure and/or sensitivity for reflex activation can shift within hours to days of the onset of hypertension (Krieger, 1970; Jones and Floras, in press).These changes are
Source: Circulation Research
Authors: M C Andresen, S Kuraoka, A M Brown
Institution: The University of Texas Medical Branch at Galveston
Language: English
Subfield: Cardiology and Cardiovascular Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
Funder: National Institutes of Health
OpenAlex ID: W2119664363