Evaluation of Blood Pressure Measured by Tail-Cuff Methods (without Heating) in Spontaneously Hypertensive Rats

Abstract

Generally, blood pressure (BP) in rats and mice is measured using the tail-cuff method after heating the animal. However, this method yields an indirect measurement of BP, and the requirement for animal heating and restraint may cause stress-induced changes in BP. [1][2][3][4] To overcome these limitations, a radiotelemetric monitoring system was developed to continuously measure cardiovascular parameters in freely moving rats.5) Bazil et al. 6) compared the cardiovascular parameters of spontaneously hypertensive rats (SHR) recorded by different methods (e.g., radiotelemetry device, cannulated arterial catheters, and indirect tail-cuff) and suggested that telemetric monitoring was a useful method of cardiovascular study that did not cause stress-induced changes in blood pressure. However, telemetric monitoring requires the implantation of a radiotransmitter in the abdomen, and the apparatus is expensive.Recently, a novel device was developed for the tail-cuff method that does not require animal heating if the ambient temperature is greater than 23°C. The goal of this study was to assess the validity of this novel tail-cuff method without animal heating (method A) when compared with the conventional heating tail-cuff method (method B; unanesthetized rats with heating), telemetry method (method C; unanesthetized restrained rats without heating), or carotid arterial catheter method (method D; anesthetized rats, carotid arterial cannulation). MATERIALS AND METHODS Animals and Operative ProceduresExperiments were performed in accordance with the Guiding Principles for the Care and Use of Laboratory Animals approved by the Japanese Pharmacological Society and Mukogawa Women's University. Male rats at 11-12 weeks of age were used, and BP and heart rate (HR) were always measured between 13:00-17:00 h.Tail-Cuff Method without Heating (Method A) Rats (SHR/Izm, Japan SLC, Inc., Shizuoka, Japan) were placed in plastic restrainers. A cuff with a pneumatic pulse sensor was attached to the tail. Rats were allowed to habituate to this procedure for 7 d before experiments were performed. BP and HR values were recorded on a Model MK-2000 (Muromachi Kikai Co., Ltd., Tokyo, Japan) without heating and were averaged from at least three consecutive readings obtained from each rat.Tail-Cuff Method with Heating (Method B) In this experiment, we measured the blood pressure and heart rate of rats used in the experiment of method A. Rats were preheated in a chamber at 35°C for 10 min, then placed in plastic restrainers. A cuff with a pneumatic pulse sensor was attached to the tail. Rats were allowed to habituate to this procedure for 7 d before experiments were performed. BP and HR values were recorded on a Model MK-2000 with heating and were averaged from at least three consecutive readings obtained from each rat.Telemetry Method (Method C) Rats (SHR/NCrj, Charles River Japan, Yokohama, Japan) were implanted with a radio transmitter (TA11PA-C40, Data Sciences, St. Paul, MN, U.S.A.). Individual rats were placed in a plastic cage on top o...

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“…Mean arterial BP (MAP, mmHg) and heart rate (HR, beats min -1 ) were measured in conscious rats using the noninvasive tail-cuff system (model BP 2000 Blood Pressure Analysis System; Visitech Systems, Apex, NC, USA) (Kubota et al, 2006;Rinaldi et al, 2013). MAP and HR were measured before, during (week 4) and at the end of the study in all rats after placing the animals on a restraint platform maintained at 33-34°C.…”

“…Four and 15 weeks postoperatively, echocardiography was performed to monitor HF. At the same time points, the BP was evaluated by use of the tail-cuff method (Kubota et al, 2006;Rinaldi et al, 2014).…”

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“…The rats were habituated to the restraint conditions by placing each into the restraint tubes three or more times in the days prior to blood pressure measurement, until the rats remained calm in the tubes. Blood pressure was measured using an inflatable tail cuff system in combination with a Model 179 Blood Pressure Analyzer (IITC Life Sciences, Woodland Hills, CA, USA; Kubota et al 2006). The average of two or three sequential blood pressure measurements was used.…”

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“…This system uses a tail cuff coupled to a mercury column. 9,10,11 In order to optimize the process, rats were restrained and placed in an incubator for five minutes with a 100W incandescent lamp, previously heated for thirty minutes.…”