Carotid sinus baroreceptor responses to recurrent trapezoidal pressure pulses

Abstract

Recurrent trapezoidal pressure pulses were applied to the carotid sinus of cats while recording from single fibers. Steady-state responses to these recurrent pressure pulses were studied. The salient features of the response were (i) a near linear rise to a dynamic peak overshoot, (ii) an adaptive fall from the peak with two distinct phases, an early rapid fall followed by a slow decay and (iii) immediate cessation of firing at the onset of the falling portion of the trapezoidal pressure pulse for all pressure velocities tested, i.e., dp dt ranging from 375 mm Hg/sec to 1850 mm Hg/sec. For positive pressure velocities, the slope of the linear rise of the steady-state response was found to be a power function of the pressure velocity, i. e., slope = K (pressure velocity) α. It was observed that α and K varied with the size of the pressure step and its initial level. The effect was such that as the magnitude of the pressure step increased, the slope decreased. These results indicate that the baroreceptor has the property of adjusting itself to steady input conditions.