Correlations between edema and the immediate and prolonged painful consequences of inflammation: therapeutic implications? / 生理学报

The precise relationship between the degree of pain and the degree of inflammation in the individual remains debated. A quantitative analysis simultaneously applied to the immediate and prolonged painful consequences of inflammation has not yet been done. Thus, the correlations between edema, nociception and hypersensitivity following an inflammatory insult were assessed in rodents. To better understand the therapeutic value of modifying specific aspects of inflammation, the effects of an anti-inflammatory drug were compared to the results. Inbred strains of mice and outbred rats received an intraplantar injection of honeybee venom and the between-group and within-group correlations were calculated for spontaneous nociceptive measures, thermal and mechanical hypersensitivity, and edema and temperature. The effect of indomethacin on the pain and inflammation measures was examined. Edema correlated with spontaneous flinching, licking and lifting of the injected paw (P< or =0.003), and not with thermal or mechanical hypersensitivity. Indomethacin affected edema and spontaneous nociception dose-dependently, and affected hypersensitivity only at the highest dose tested (P< 0.05). These results suggest that edema may contribute only to immediate spontaneous nociceptive responses to an inflammatory insult, and not to the more clinically relevant prolonged hypersensitivity. This analysis represents a method for determining which inflammatory processes are the most promising therapeutic targets against the multiple painful consequences of inflammation.

Inhibitory effects of spinal propofol on the responses of spinal dorsal horn neurons in normal rats / 生理学报

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.