1. Rabbits received intracisternal injections of 5,6-dihydroxytryptamine (5,6-DHT) in order to ablate central serotonergic nerves and deplete central serotonin stores. Depletion was most marked in the spinal cord where serotonin concentration was reduced to less than 50% of that in rabbits given control injections.
2. In normal rabbits, intracisternal 5,6-DHT caused a transient reduction in arterial pressure, which was maximal 1 week after injection.
3. Intracisternal 5,6-DHT completely prevented the neurogenic hypertension produced by sinoaortic denervation in control animals and reversed it when given after sustained neurogenic hypertension had developed in denervated animals. These studies suggest that central serotonergic neurons participate in the baroreceptor reflex arc.
4. Intracisternal 5,6-DHT did not modify the renal hypertension that follows bilateral renal wrapping.