Dose-dependent effects of propofol on renal sympathetic nerve activity, blood pressure and heart rate in urethane-anesthetized rabbits.
To evaluate the role of the autonomic nervous system in hemodynamic changes after propofol bolus injection, we used direct recordings of renal sympathetic nerve activity to examine the dose-dependent effects of propofol (2.5, 5, 10, and 20 mg/kg) on heart rate, mean blood pressure and renal sympathetic nerve activity in urethane-anesthetized rabbits. The animals were divided into four groups: animals with an intact neuraxis (intact group), cervical vagal nerve-sectioned animals (vagotomy group), carotid sinus and aortic-nerve sectioned animals (SAD group), and animals with SAD plus vagotomy (SADV group). Heart rate did not change significantly even after administration of 2.5 and 5 mg/kg but decreased markedly on 20 mg/kg injection in all groups. The intact and vagotomy groups had augmented renal sympathetic nerve activity with insignificant changes in mean blood pressure after 5 mg/kg injection of the agent. Insignificant changes of renal sympathetic nerve activity but a remarkable decrease of mean blood pressure appeared after 10 mg/kg propofol. Sustained hypotension in parallel with a profound depression of renal sympathetic nerve activity developed at the dose of 20 mg/kg. In SAD and SADV groups, however, dose-dependent depressions of renal sympathetic nerve activity were accompanied by decreases of mean blood pressure. These results suggest the following: (1) propofol-induced hypotensive effects are probably produced by the central-mediated sympathetic depression. (2) The baroreceptor reflex may be preserved at the lower dose of the agent. (3) Heart rate does not change significantly unless a large dose of propofol is used. The difference in effects on heart rate and on mean blood pressure may denote a greater inhibition of sympathetic vascular outflow than of the cardiac sympathetic outflow regulating cardiac rate and contractility. This hypothesis needs further clarification.
Xu
H
H
Department of Anesthesiology and Emergency Medicine, and Intensive Care Unit, Kagawa Medical University, 1750-1, Ikenobe, Miki, Japan.
Aibiki
M
M
Yokono
S
S
Ogli
K
K
D000758:Anesthesia; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D003714:Denervation; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects*; D007668:Kidney / Q000294:innervation*; D015742:Propofol / Q000494:pharmacology*; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000502:physiology; D014520:Urethane / Q000494:pharmacology; D014628:Vagotomy; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology / Q000601:surgery
D018686:Anesthetics, Intravenous; D014520:Urethane; D015742:Propofol