Ramp rate of blood pressure changes does not affect aortic afferent sensitivity in anesthetized rats |
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| Authors: | Hidefumi Waki Tsuyoshi Shimizu Masao Yamasaki Kiyoaki Katahira Shinichiro Katsuda Jaimie W. Polson Masanobu Maeda |
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| Affiliation: | 1. Department of Physiology-II, Wakayama Medical University School of Medicine, 811-1, Kimiidera, Wakayama City 641-8509, Japan;2. Shimizu Institute of Space Physiology, Suwa Maternity Clinic, 112-13, Shimosuwa-machi, Nagano 393-0077, Japan;3. Cellular and Integrative Physiology, Fukushima Medical University, 1 Hikari-ga-oka, Fukushima 960-1247, Japan;4. Experimental Animal Center, Fukushima Medical University, 1 Hikari-ga-oka, Fukushima 960-1247, Japan;5. Department of Clinical Science at South Bristol, Bristol Heart Institute, School of Medical Sciences, University of Bristol, Bristol BS2 8HW, UK |
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| Abstract: | To investigate whether the rate of change in blood pressure affects the sensitivity of the aortic baroreceptor afferent response, the change in aortic nerve activity (ANA) to two different rates of ramp increase in mean blood pressure (MBP), elicited by phenylephrine administration, was determined in the rat under urethane (1.5 g kg−1) anesthesia. The sensitivity of the increase in ANA following a rapid (average ramp rate, 9.14 ± 0.60 mmHg s−1, n = 11) or gradual (1.78 ± 0.24 mmHg s−1, n = 11) increase in MBP was 2.03 ± 0.14% and 1.81 ± 0.20% of baseline mmHg−1, respectively. These values were not significantly different from each other (P = 0.16). Furthermore, we found no correlation between the rate of ramp increase in MBP and the sensitivity of the increase in ANA (r = 0.24, P = 0.29, n = 22). These results suggest that, at least within the normal physiological range of MBP, the rate of the ramp change in blood pressure does not affect aortic baroreceptor afferent sensitivity in the anesthetized rat. |
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| Keywords: | Aortic nerve activity Baroreceptors Baroreceptor reflex Blood pressure Rat |
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