[The possible mechanism of the noradrenaline enhancement of the arterial baroreceptor reflex].

In anaesthetized cats intravenous infusion of norepinephrine induced the increase in arterial pressure and suppression of renal nerve electrical activity. The latter followed the infusion was stopped and arterial pressure returned toward control. The baroreflex suppression of sympathetic activity associated with norepinephrine increased in the case of preliminary mechanical damage to blood-brain barrier. Duration and intensity of the sympathetic activity suppression following norepinephrine infusion depended on the magnitude of hypertensive reaction and the rate of elevating in arterial pressure under the action of norepinephrine. Norepinephrine at the similar concentrations did not depress sympathetic activity if the arterial pressure was stabilized on the resting level. These data support the supposition that the elevation of arterial pressure due to norepinephrine infusion increases the ability of catecholamine to enter brain and in this way activates the central limb of arterial baroreceptor reflex.