ABSTRACT
Objective To investigate the role of GABAAα3and GABAB receptors in the ventrolateral periaqueductal gray in the development of paw acute pain in rats.Methods Twelve male SD rats, weighing 280~320 g, were randomly divided into two groups: normal saline group (group NS), formaldehyde-induced pain group (group F), 6 rats in each group.In group F, rats were subcutaneously injected with 2% formaldehyde 50 μl into the ventral surface of right hind paw to induce periphery inflammatory pain.In group NS, rats were subcutaneously injected with normal saline into the ventral surface of right hind paw.Mechanical threshold was assessed using von Frey hairs for every ten minutes.The rat pain behavior scores were recorded for every five minutes.The thickness of skin and skin temperature were recorded for every fifteen minutes.Results Mechanical hyperalgesia were induced in group F after formalin injection into right hind paw.Compared with group NS, rat pain behavior scores were increased significantly in group F at all time points after injection, mechanical threshold were decreased significantly in group F at 10-60 min after injection, the temperature of the skin and the skin thickness were increased significantly in group F at 15-60 min after injection (P<0.05), the levels of the expression of GABAAα3 and GABAB were significantly increased in group F (P<0.05).Conclusion GABAAα3and GABAB receptors mediates formalin-induced hyperalgesia at ventrolateral portion of the PAG (vlPAG) of rats.