Transfer function analysis of carotid sinus baroreceptor transduction

The carotid sinus baroreflex is one of the most important negative feedback systems that regulate arterial pressure. The neural arc transfer function from carotid sinus pressure (CSP) input to efferent sympathetic nerve activity shows a gain increase of approximately 10 dB when input frequency increases from 0.01 to 0.5 Hz. The transfer gain of the neural arc decreases in the frequency range above 0.8 Hz. The aim of the present study was to elucidate the extent of contribution of the carotid sinus baroreceptor transduction to the determination of the neural arc dynamic characteristics. In 7 anesthetized rabbits, we isolated the right carotid sinus and controlled CSP while recording afferent nerve activity (ANA) from the carotid sinus nerve. CSP was randomly assigned to either 80 or 120 mmHg with a switching interval of 50 ms according to a binary white noise signal for 15 min. The transfer function from CSP to ANA was estimated in the frequency range from 0.01 to 3 Hz. The transfer function showed a gain increase of approximately 4.6 dB when input frequency increased from 0.01 to 0.3 Hz. The transfer gain remained relatively constant up to 3 Hz. These results suggest that the carotid sinus baroreceptor transduction partly contributes to the gain increase of the baroreflex neural arc in the frequency range from 0.01 to 0.5 Hz but not the gain decrease above 0.8 Hz.