Abstract
Previously, the fine structure of the carotid body, the experimental sclerosis of the carotid sinus wall, circulatory effects of carotid occlusion and adrenergic blocking agents effects for the carotid baroreceptor, were studied in this clinic. This time, circulatory changes due to carotid sinus reflex by electrical stimulation (square wave; 8v., 20-50cps) of the carotid sinus wall in situ canine carotid artery were investigated
(1) Systolic arterial blood pressure was lowered by 33.7mm.Hg from average 143mm.Hg. Diastolic arterial pressure was decreased by 21.0mm.Hg from the level of 74.8mm.Hg. P-value was less than 0.001. Coronary blood flow was also decreased 5.5ml./min. from average mean flow 30.4ml./min. (P less than 0.001). Coronary resistance was decreased 0.27mm.Hg/ml./min. from average 3.22mm.Hg/ml./min. (P less than 0.001). Cardiac output was decreased insignificantly. Left intracardiac pressure was reduced by 8.9mm.Hg (P less than 0.01). Its max dp/dt was decreased (P less than 0.01). The dp/dt/IIT was reduced by 0.06 (per cent change, 18.18%) from average 0.33. The change of the left ventricular tension measured by the straingauge arch was insignificant. The R-R and P-R intervals were slightly prolonged in the second lead of the electrocardiogram (P less than 0.001). The myocardial oxygen consumption was altered to decrease. Arterial blood catecholamine was apt to decrease.
(2) After the administration of propranolol (0.2mg./Kg.), carotid sinus reflex by the electrical stimulation did not cause the changes of intracardiac pressure and max dp/dt but those of arterial blood pressure and coronary blood flow. Cervical vagotomy inhibited these changes.
(3) It should be noted here that these decreases of cardiac work, myocardial oxygen requirement and diastolic coronary resistance are effective for the angina pectoris through the adrenergic and the cholinergic nerves with catecholamine change.
