SYMPATHETIC-NERVE TRAFFIC CORRELATES WITH THE RELEASE OF NITRIC-OXIDEIN HUMANS - IMPLICATIONS FOR BLOOD-PRESSURE CONTROL

1. Resting human sympathetic vasoconstrictor traffic displays large re producible interindividual differences which are similar in nerves to muscle, heart and kidney. In spite of this there is no correlation bet ween levels of blood pressure and sympathetic traffic. To test the hyp othesis that the pressor effect of the vasoconstrictor activity is cou nteracted by a circulating dilating factor we measured muscle nerve sy mpathetic activity (MSA) and an indicator of nitric oxide release (pla sma nitrate) in healthy young males. 2. Sympathetic activity was recor ded with the microneurographic technique in the peroneal nerve and a f orearm venous plasma sample was obtained in twenty-one normotensive ma les aged 21-28 years. Plasma nitrate was analysed by gas chromatograph y and mass spectrometry. 3. There was a positive linear correlation be tween the plasma nitrate concentration and the strength of MSA both wh en the nerve activity was expressed as bursts per minute and bursts pe r 100 heart beats (r = 0.51, P = 0.02 and r= 0.46, P = 0.04, respectiv ely). 4. The data suggest that the stronger the sympathetic activity t he higher the release of the dilating substance, nitric oxide. This wo uld be expected to counteract vasoconstrictor effects oi the nerve tra ffic and thereby contribute to the lack of relationship between restin g levels of MSA and blood pressure. We speculate that altered coupling between sympathetic traffic and nitric oxide release may cause abnorm al peripheral resistance, e.g. in hypertension.