Increased extracellular concentration of norepinephrine in the hypothalamus by sinoaortic denervation.

To determine whether baroreflex can affect the norepinephrine system in the hypothalamus, the extracellular concentration of norepinephrine were measured by the brain dialysis technique in sinoaortic denervated rats (SAD). Twenty-four hours after sinoaortic denervation, systolic blood pressure and heart rate were significantly elevated, and norepinephrine concentration in perfusate of the posterior hypothalamus was significantly higher in SAD rats than in sham-operated rats. These results suggest that baroreflex could modify the activity of noradrenergic neuron projecting to the posterior hypothalamus.