[Effect of cervical sympathetic stimulation on the carotid sinus reflex in rabbits].

Effects of electrical stimulation of cervical sympathetic nerves(CSN)on thecarotid sinus baroreflex were examined in 36 anesthetized rabbits.The resultsobtained were as follows:(1)Electrical stimulation of CSN abolished or reversedthe carotid-occlusion pressor reflex,as indicate by decrease of △ BP from+39.5±3.6 to-0.31±5.4 mmHg(P0.001).(2)The carotid sinus baroreceptor-heartrate reflex induced by intravenous injections of phenylephrine was augmentedby CSN stimulation.(3)By distending isolated carotid sinuses bilaterally underdifferent levels of pressure(50—200mmHg),the curve relating carotid sinus pressure(CSP)to systemic mean arterial pressure(MAP)was constructed.Stimulationof CSN always resulted in a downward shift of CSP—MAP curve(P0.01),thussuggesting an increase in the activity of carotid sinus baroreceptor(CSB).(4)Following the bilateral section of CSN,arterial pressure was definitely increased,which might be explained by the loss of tonically regulatory effect of CSN on theCSB activity.Our findings suggested that CSN might modulate the CSB activityindirectly by increasing the tension of sinus wall.