Evidence of differential control of renal and lumbar sympathetic nerve activity in conscious rabbits.
We have explored the possibility that renal sympathetic nerve activity (RSNA) and vasomotor sympathetic nerve activity are differentially regulated. We measured sympathetic nerve activity (SNA) to the kidney and the hind limb vasculature in seven conscious rabbits 6-8 days after the implantation of recording electrodes. Acute infusion of N(G)-nitro-L-arginine methyl ester (L-NAME) (6 mg.kg(-1).min(-1) for 5 min) led to an increase in blood pressure (from 66 +/- 1 to 82 +/- 3 mmHg) and a decrease in heart rate (from 214 +/- 15 to 160 +/- 13 bpm). L-NAME administration caused a significantly greater decrease in RSNA than lumbar sympathetic nerve activity (LSNA) (to 68 +/- 14% vs. 84 +/- 4% of control values, respectively). Volume expansion (1.5 ml.kg(-1).min(-1)) resulted in a significant decrease in RSNA to 66 +/- 7% of control levels but no change in LSNA (127 +/- 20%). There was no difference in the gain of the baroreflex curves between the LSNA and RSNA [maximum gain of -7.6 +/- 0.4 normalized units (nu)/mmHg for LSNA vs. -7.9 +/- 0.75 nu/mmHg for RSNA]. A hypoxic stimulus (10% O2 and 3% CO2) led to identical increases in both RSNA and LSNA (195 +/- 40% and 158 +/- 21% of control values, respectively). Our results indicate tailored differential control of RSNA and LSNA in response to acute stimuli.
Ramchandra
Rohit
R
Circulatory Control Laboratory, Department of Physiology and Bioengineering Institute, University of Auckland, Private Bag 92019, Auckland, New Zealand.
Barrett
Carolyn J
CJ
Guild
Sarah-Jane
SJ
Malpas
Simon C
SC
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003243:Consciousness / Q000502:physiology; D005246:Feedback / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D007668:Kidney / Q000294:innervation* / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D011817:Rabbits; D012018:Reflex / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D014666:Vasomotor System / Q000502:physiology*
D009569:Nitric Oxide