Servoanalysis of Carotid Sinus Reflex Effects on Peripheral Resistance

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Abstract
In vagotomized, anesthetized animals, the carotid sinus receptors were subjected to changes in maintained pressure and to sine waves and steps of pressure. The observed properties of the carotid sinus reflex are: During either maintained pressure changes or pressure sine waves,the amplification of the reflex has a prominent peak at a certain input pressure, and is less at higher or lower input pressures. Amplification ranged from +1 to +15 in the cat and from +0.8 to +8 in the dog. A step change in input pressure induces no response for about two seconds. The output then goes slowly to a new level; moving oppositely to the change in input, there is at times some early overshoot. The sine wave response to imposed sine waves of pressure is maximal and exactly out of phase with the input when the input waves are of low frequency (0.01 cycles/sec and slower). At higher input frequencies, the amplitude of the output decreases, and the output lags the input by a larger phase angle. At 0.08 to 0.10 cycles/sec the calculated phase lag increases by 90 degrees, and the amplitude of the output may be only one-tenth of the input (calculated phase lag is the measured lag corrected for delay). Beyond 0.08 to 0.15 cycles/ sec there is no sine wave response. As the frequency of the sine wave input to the carotid sinus is increased, the mean output pressure falls. This effect (rectification) continues after the output sine wave response disappears.