Réactions cardio-vasculaires du rat à I'hypercapnie ventilatoire

Abstract

1. Two populations of albino rats: normal and treated by phentolamine, or normal and vagotomized, have inhaled normoxic or hyperoxic mixtures with 3, 15 or 30 % CO₂ during 5 min.

2. Bradycardia is proportional to CO₂ concentration, from 3 % CO₂. It is not suppressed by vagotomy.

3. Systemic arterial pressures, both systolic and diastolic, are decreased by 15 % CO₂. This hypotension is long lasting. At 30 % CO₂, immediate hypotension is followed by progressive recovery. After phentolamine, the return to normal is abolished.

4. Bradycardia is caused by CO₂ or acidosis acting directly on the pace-maker cells. Variations of the systemic blood pressure are explained by an interference between a direct vasodilatation and a vasoconstriction due to sympathetic centres stimulation by CO₂.