Cardiac receptors with non-medullated vagal afferents in the rat

Publisher Website
Google Scholar
Abstract
The characteristics of 22 atrial receptors in 15 normotensive adult male Wistar rats were studied. All receptor afferents were included in the C-fiber group with conduction velocities from 0.4-1.2 m/s. No atrial medullated receptors or ventricular C-fiber endings were found. Two receptors were located in right atrium and 2 receptors throughout left atrium. Upon elevation of the left atrial pressure the receptor discharge was markedly elevated with thresholds from 2.5-9 mmHg in mean left atrial pressure. Of the atrial receptors 10 displayed a clear cardiac rhythmicity upon activation and the discharge correlated with the v-wave, indicating distension as the cause of receptor activation. The maximal firing rate in most receptors was very high (up to 70 Hz) but 8 receptors had maximal firing rates below 25 Hz. The low frequency receptors had higher threshold and showed a more irregular firing. There is a substantial population of atrial receptors with vagal non-medullated afferents in the rat heart and the thresholds for many receptors are so low that they tend to be active during normal conditions.