The Techniques to Continuously Measure the Cardiac Functions (Electrocardiogram and Arterial Blood Pressure) of the Conscious Rats

Use for the Studies during Exposurc to Air Pollutants

Abstract

We devised techniques to continuously record heart rate (HR) and blood pressure (BP) of the conscious and unrestrained rats in order to study effects of environmental pollutant on the cardiac functions. Essentially, BP was measured by means of a polyethylene catheter which was inserted into the femoral artery, and HR was calculated from electrocardiogram which was recorded with chest bipolar lead. Operations to insert the catheter into the artery and attach the electrodes were done 1 day before the recordings, and rats could move freely in their cages during the recordings.
The following were observed in the rats of Wistar strain wiht these techniques:(1) Age difference was almost evident in HR, but not in BP, in normotensive rats of 4-28 weeks old, and evident in both HR and BP in spontaneously hypertensive rats of 4-16 weeks old.(2) Reproducibility of the measurements was fairly good within 3 days after the operation, although HR tended to slightly decrease.(3) HR and BP were found to be almost constant during 3-hr exposure to filtered air in an exposure chamber.(4) Anesthesia with pentobarbital sodium was found to produce profound effects of HR and BP.
We concluded from the above results that effects of environmental pollutants on the cardiac functions of rats should be studied in the unrestrained condition without the anesthesia, and the present techniques were suitable for such studies during short-time exposure. With these techniques, we preliminarily found the depressive effects of ozone of 1 ppm on HR and BP of the rats.