RESUMO
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.