Propofol directly depresses lumbar dorsal horn neuronal responses to noxious stimulation in goats.
OBJECTIVE
We tested the hypothesis that propofol, acting in the brain, would either enhance, or have no effect, on lumbar dorsal horn neuronal responses to a noxious mechanical stimulus applied to the hindlimb. We recorded the response of lumbar dorsal horn neurons during differential delivery of propofol to the brain and torso of goats.


METHODS
Goats were anesthetized with isoflurane and neck dissections performed which permitted cranial bypass. A laminectomy was made to allow microelectrode recording of lumbar dorsal horn neuronal activity. Isoflurane was maintained at 0.8+/-0.1% to both head and torso throughout the study. During cranial bypass propofol was separately administered to the torso (1 mg x kg(-1), n = 7; 3.75 mg x kg(-1), n = 8) or cranial (0.04 mg x kg(-1), n = 7; 0.14 mg kg(-1), n = 8) circulations.


RESULTS
Propofol administered to the torso depressed dorsal horn neuronal responses to noxious stimulation: low dose: 500+/-243 to 174+/-240 impulses x min(-1) at one minute post-injection, P<0.001; high dose: 478+/-204 to 91+/-138 impulses x min(-1) at one minute post-injection, P<0.05). Propofol administered to the cranial circulation had no effect: low dose: 315+/-150 to 410+/-272 impulses x min(-1), P>0.05; high dose: 462+/-261 to 371+/-196 impulses x min(-1), P>0.05.


CONCLUSIONS
These data indicate that propofol has a direct depressant effect on dorsal horn neuronal responses to noxious stimulation, with little or no indirect supraspinal effect.
Antognini
J F
JF
Department of Anesthesiology and Pain Management, University of California, Davis 95616, USA. jfantognini@ucdavis.edu
Wang
X W
XW
Piercy
M
M
Carstens
E
E
D000704:Analysis of Variance; D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects; D002492:Central Nervous System Depressants / Q000494:pharmacology; D002560:Cerebrovascular Circulation; D006041:Goats; D006614:Hindlimb / Q000294:innervation; D007267:Injections; D007530:Isoflurane / Q000008:administration & dosage; D007796:Laminectomy; D016014:Linear Models; D008839:Microelectrodes; D009434:Neural Pathways / Q000187:drug effects; D010146:Pain / Q000503:physiopathology*; D020671:Posterior Horn Cells / Q000187:drug effects*; D015742:Propofol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D013909:Thorax / Q000098:blood supply
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D002492:Central Nervous System Depressants; D007530:Isoflurane; D015742:Propofol