GABA_A receptor partially mediated propofol-induced hyperalgesia at ventrolateral periaqueductal gra Article Abstract
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Published: February 28, 2006
Aim To observe the effects of propofol on nociceptive response at ventrolateral periaqueductal gray(vlPAG) of rats and the possible role of GABA_A receptor in this prosses.Methods Sprague-Dawley(SD) female rats were randomized into each group.Bicuculline and propofol were microinjected into ventrolateral periaqueductal gray(vlPAG).The noxious response was evaluated by hot plate and formalin test.Fos-like immunoreactivity(FLI) neurons expressed in spinal dorsal horn(DH) induced by formalin intraplantar injection(sc) of one hindpaw were used as a neuroactive marker to observe the effects of propofol on the noxious transmission in DH.Results In hot-plate test,the hyperalgesia induced by propofol(10 g·L~(-1)) vlPAG microinjection was significantly antagonized about(70%),(71%) at 10 and 20 min after (bicu-)culline(25 mg·L~(-1)) vlPAG microinjection(P<0.01).In formalin test,the increased formalin pain scores induced by propofol vlPAG microinjection were antagonized about 57%(P<0.05) after bicuculline(25 mg·L~(-1)) vlPAG microinjection at 60 min after formalin injection.In immunohistochemistry test,the number of formalin-induced FLI neurons,which were induced by formalin intraplantar injection sc of one hindpaw in same lateral superficial layer of DH,was significantly enhanced by propofol vlPAG microinjection(10 g·L~(-1),P<0.01).This effect was antagonized(P<0.01) by bicuculline pretreatment at same site.Conclusion GABA_A receptor partially mediates propofol-induced hyperalgesia at vlPAG in rats.The effects of propofol on the number of formalin-induced FIL in DH superficial layer are in accordance with the effects in the praxiology test.