Inhibitory effects of spinal propofol on the responses of spinal dorsal horn neurons in normal rats.
Spinal dorsal horn neurons play an important role in the processing of sensory information and are also targets of modulation by both endogenous and exogenous drugs. Propofol is an intravenous anesthetic and whether it has direct modulatory actions on sensory neuronal responses of the spinal cord dorsal horn has not been well studied. In the present study, a single dose (0.5 micromol) of propofol dissolved in dimethyl sulfoxide (DMSO) was directly applied onto the dorsal surface of the spinal cord and its effect was evaluated in 25 wide-dynamic-range (WDR) neurons and 10 low-threshold mechanoreceptive (LTM) neurons by using extracellular single unit recording technique in sodium pentobarbital anesthetized rats. Compared with the DMSO treatment, propofol produced a significant inhibition of WDR neuronal activity evoked by both noxious heat (45, 47, 49 or 53 degrees C, 15 s) and mechanical (pinch, 10 s) stimuli applied to their cutaneous receptive fields (cRF) on the ipsilateral hind paw skin. To investigate whether propofol exerts a modulatory effect on non-nociceptive afferent-mediated activity, the responses of WDR or LTM neurons to non-noxious brush and pressure were also evaluated. The non-noxious mechanically-evoked responses of both WDR and LTM neurons were significantly suppressed by propofol. The present results indicate that propofol has direct actions on the dorsal horn neurons of the spinal cord in rats. However, since both non-nociceptive and nociceptive afferent-mediated activity can be suppressed, the spinal effects of propofol are not likely to be specifically associated with anti-nociception.
Pain Research Center, Institute of Neuroscience, Fourth Military Medical University, Xi'an, Shaanxi 710032, China.
Yan-Yan
YY
Sun
Kai-Cheng
KC
Li
Jun
J
Chen
D018686:Anesthetics, Intravenous; D000818:Animals; D004121:Dimethyl Sulfoxide; D004594:Electrophysiology; D008297:Male; D008465:Mechanoreceptors / Q000187:drug effects*; D009619:Nociceptors / Q000502:physiology*; D020671:Posterior Horn Cells / Q000502:physiology*; D015742:Propofol / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000502:physiology*
D018686:Anesthetics, Intravenous; D015742:Propofol; D004121:Dimethyl Sulfoxide