Responses to Carotid Stimuli in Humans

SUMMARY Angiotensin II is a potent vasoconstrictor and has profound effects on autonomic neural mechanisms in experimental animals. Human carotid baroreflex control of arterial pressure and heart period was examined before and after acutely decreasing angiotensin II levels by adminis-tering 50 mg of oral captopril, an angiotensin converting enzyme inhibitor. Carotid baroreceptor stimuli were delivered by a neck chamber worn by 14 normotensive volunteers. Four subjects received placebo. Arterial pressure responses to carotid distent ion and tachycardia in response to carotid compression were not changed in captopril or placebo groups; however, there was an augmented bradycardie response to carotid stretch in captopril-treated subjects. These results indicate that captopril has an asymmetrical effect on carotid baroreflex function and suggest that enhanced barore-flex mediated bradycardia is due to a reduction in central nervous system angiotensin II levels by captopril, which augments vagal-cardiac responses to carotid stimuli. (Hypertension 7: 602-606, 1985) KEY WORDS • angiotensin • baroreceptor • blood pressure • carotid sinus A NGIOTENSIN II is a potent vasoconstrictor / \ agent that has been shown to have an impor