Circulatory responses to acute hypoxia in spontaneously hypertensive and normotensive rats

Experiments were carried out on 6-7 months old spontaneously hypertensive rats (SHR) (NIbm) of the Okamoto-Aoki strain and age matched normotensive control rats (NCR) of the same age group. Acute hypoxia produced bradycardia and a fall of blood pressure in artificially ventilated NCR and a biphasic heart rate response (acceleration-deceleration) in SHR. After bilateral vagotomy or atropine administration a pressor response to hypoxia occurred in NCR and SHR. We conclude that adult SHR exhibit reduced sensitivity of the cardio-vagal component of the arterial chemoreflex.