RESUMEN
Objective To investigate the expression of γ-aminobutyric acid A receptor α1 subunit (GABAAα1) in the ventrolateral periaqueductal gray (vLPAG) in rats with formalin-induced acute pain. Methods The rats were randomly divided into two groups:control group(group C) and formalin-induced pain group(group F),12 rats in each group:0.9% sodium chloride solution or 2% formaldehyde 50 μL was injected into the ventral surface of right hind paw respectively. The pain scores were recorded for every 5 minutes and the mechanical pain threshold were recorded for every 10 minutes until 1 h. The expression levels of GABAAα1in vLPAG were determined by Western blot analysis in each group.Results The rats in formalin group showed significant nociceptive behaviors immedi-ately, such as paw withdrawal and/or paw licking. Results demonstrated that the rats exhibited a biphasic response to pain. The pain behavior scores in group F were significantly higher than that in group C (P<0.05),and the mechanical pain threshold in group F was decreased after injection compared with group C(P<0.05). The expression of GABAAα1 protein in group F was significantly higher than that in group C (P<0.05).Conclusions The up-regulation of GABAAα1 expression in ventrolateral periaqueductal gray is associated with the decrease of pain threshold in rats with acute pain.
RESUMEN
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