Role of renal sympathetic nerve activity in hypertension induced by chronic nitric oxide inhibition.
Nitric oxide levels are diminished in hypertensive patients, suggesting nitric oxide might have an important role to play in the development of hypertension. Chronic blockade of nitric oxide leads to hypertension that is sustained throughout the period of the blockade in baroreceptor-intact animals. It has been suggested that the sympathetic nervous system is involved in the chronic increase in blood pressure; however, the evidence is inconclusive. We measured renal sympathetic nerve activity and blood pressure via telemetry in rabbits over 7 days of nitric oxide blockade. Nitric oxide blockade via N(omega)-nitro-L-arginine methyl ester (L-NAME) in the drinking water (50 mg x kg(-1) x day(-1)) for 7 days caused a significant increase in arterial pressure (7 +/- 1 mmHg above control levels; P < 0.05). While the increase in blood pressure was associated with a decrease in heart rate (from 233 +/- 6 beats/min before the L-NAME to 202 +/- 6 beats/min on day 7), there was no change in renal sympathetic nerve activity (94 +/- 4 %baseline levels on day 2 and 96 +/- 5 %baseline levels on day 7 of L-NAME; baseline nerve activity levels were normalized to the maximum 2 s of nerve activity evoked by nasopharyngeal stimulation). The lack of change in renal sympathetic nerve activity during the L-NAME-induced hypertension indicates that the renal nerves do not mediate the increase in blood pressure in conscious rabbits.
Ramchandra
Rohit
R
Circulatory Control Laboratory, Department of Physiology, University of Auckland, Private Bag 92019, Auckland, New Zealand.
Barrett
Carolyn J
CJ
Guild
Sarah-Jane
SJ
McBryde
Fiona
F
Malpas
Simon C
SC
D000818:Animals; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000139:chemically induced; D007668:Kidney / Q000187:drug effects / Q000294:innervation*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors*; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000378:metabolism*; D013686:Telemetry; D013997:Time Factors
D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester