Cardiovascular responses induced by injection of endothelin-1 into the superior colliculus of rats

Microinjection of endothelin-1 (1-10-100 pmol) into the superficial layer of the superior colliculus of anaesthetised rats caused dose-dependent decreases in blood pressure. This is unlikely to be a non-specific effect, for angiotensin II (1 nmol) caused increases in blood pressure. Injection of endothelin-1 (10 pmol) into the superior colliculus also caused falls in renal blood flow as measured by an ultrasonic flow probe. Decreases in blood pressure and falls in renal blood flow induced by injection of endothelin-1 into the superior colliculus were unaffected by bilateral vagotomy suggesting that attenuations in the activity of the sympathetic nervous system were involved in these events.