1. When the sino-aortic afferents are intact, desynchronized sleep causes a small decrease in the blood pressure, a vasodilatation in the mesenteric and renal beds, and a vasoconstriction in the external iliac bed.
2. After sino-aortic deafferentation desynchronized sleep causes a larger fall in the blood pressure, a greater vasodilatation in the mesenteric and renal beds, and a vasodilatation replaces the vasoconstriction in the external iliac bed.
3. The sino-aortic reflexes play an active role in controlling circulation during desynchronized sleep by opposing the centrally induced reduction in adrenergic sympathetic tone. This effect of sinoaortic reflexes is similar on both visceral and muscular vessels. In addition, the muscular bed, but not the visceral one, is regulated by a spinal reflex vasoconstriction mechanism which is apparent only when the sino-aortic reflexes are intact.