Summary—In anaesthetized animals, systemic injection of ET1at doses from 3 to 100 ng·kg−1provoked only a transient hypotensive effect. At 300 ng·kg−1we observed the classical biphasic effect, consisting of a transient lowering of the arterial pressure followed by a long‐lasting hypertensive effect. Direct injection of the peptide into the vertebral artery of anaesthetized animals only affected arterial pressure (AP) when the blood‐brain barrier was permeabilised. Under these conditions, a dose‐dependent decrease in AP was observed, which was not associated with a significant effect on the heart rate. Micro‐injections of the peptide in the medullary nucleus reticularis lateralis area (NRL), a medullary vasopressive centre, at doses of 30 to 60 ng·kg−1led to a significant reduction in mean arterial pressure (MAP) (17 ± 4% and 36.5 ± 6%) respectively without a significant change in heart rate. These effects lasted less than 2 hours. These results suggest a possible role of ET1as a neuromodulator involved in the central regulation of vasomotor ton
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