Dogs under chloralose anesthesia show augmented reflex responses of systolic arterial pressure, mean arterial pressure, diastolic arterial pressure, and pulse rate to bilateral occlusion of the common carotid arteries over the responses of these same parameters before any anesthesia. Hyporeflexia, as indicated by these parameters, is observed when the anesthetic is chloralose and urethan, pentobarbital, or thiobarbital. Less variance in the responses as a result of alteration of the anesthetic level is observed with chloralose or pentobarbital anesthesia than with chloralose and urethan or thiobarbital anesthesia. If either chloralose or pentobarbital is to be used in studies involving the carotid sinus reflex, due consideration must be given to the 8% increase in response of mean arterial pressure under chloralose anesthesia as well as the 9% decrease in response of this same parameter under pentobarbital anesthesia.

The quantitative changes in systolic pressure, diastolic pressure, mean pressure and pulse rate produced by 128 bilateral occlusions of the common carotid arteries in nine conscious dogs are reported. The average of the values measured before occlusion were: systolic pressure, 176 mm Hg; diastolic pressure, 80 mm Hg; mean pressure, 117 mm Hg; pulse rate, 101 pulses/min. Increases of 28%, 50%, 39%, and 28%, respectively, were obtained as a result of the occlusions.

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