Carotid sinus reflex in cat: effect of prior external carotid artery clamping

Intrasinusal and systemic arterial pressure changes resulting from occlusion of the common carotid arteries (CCO) in vagotomized cats were recorded and compared with those in which the external carotid arteries were previously clamped. The CCO responses were similar under chloralose and pentobarbital anesthesia, and were unaltered by positive-pressure respiration. Prior bilateral external carotid artery clamping (ECC) significantly reduced the initial fall in intrasinusal pressure and the reflex pressor response. Injections of acetic acid into the sinus region reduced the reflex pressor response despite a greater fall in intrasinusal pressure after CCO. Following acid treatment, prior ECC generally reduced the reflex pressor response to a lesser degree than before treatment. It is concluded that in vagotomized cats, there is no difference between chloralose and pentobarbital anesthesia or positive-pressure and spontaneous respiration on the CCO response. The magnitude of the reflex pressor response apparently depends on the degree of baroreceptor deactivation and chemoreceptor activation. The results are discussed further in terms of differences between the cat and the dog.