The Role Of Atp-sensitive Potassium Channel In Allodynia Associated With Neuropathic Pain And Chronic Postthoracotomy Pain

Objective:To evaluate the role of spinal dorsal horn neural ATP-sensitive potassium channel in allodynia associated with neuropathic pain and chronic postthoracotomy pain.Methods:1. 15 adult male Sprague-Dawley rats, weighing 220 ~ 300g, were randomly divided into two groups (10 for CCI group and 5 for sham group). Behavioral test: All of the rats were measured mechanical withdrawal threshold (MWT) the day before surgery. Then from the first day post-surgery, all animals were tested for 14 days for MWT using calibrated Von Frey filaments applied to the incision site. The results were compared between two groups. Immunohistochemical studies: The L4-5 spinal cords of hyperalgesic rats from CCI group and rats from sham group (both obtained at 14 day post-surgery) were transversely sectioned, then were evaluated by immunohistochemistry. The expression densities of KATP in the membrane of spinal dorsal horn neurons were compared between two groups. 2. 15 adult male Sprague-Dawley rats, weighing 220 ~ 300g, were randomly divided into two groups (10 for CPTP group and 5 for Sham group). Behavioral test: All of the rats were measured mechanical threshold the day before surgery. Then from the first day post-surgery, all animals were tested for 14 days for mechanical allodynia using calibrated Von Frey filaments applied to the incision site. The results were compared between two groups. Immunohistochemical studies: The thoracic spinal cords of hyperalgesic rats from CPTP group and rats from Sham group (both obtained at 14 day post-surgery) were transversely sectioned, then were investigated by KATP immunohistochemistry. The expression densities of KATP in the membrane of spinal dorsal horn neurons were compared between two groups.Results:1. Behavioral test: There was no difference in mechanical allodynia between each group before surgery. Compared to the preoperative baseline, from the 5 day post-surgery, mechanical allodynia was developed, and was kept to the 14 day post-surgery in all of the CCI group animals (P<0.05) , but none in sham animals (P>0.05). Compared to the preoperative baseline, from the 5 day post-surgery, mechanical allodynia was developed, and was kept to the 14 day post-surgery in 7 of 10 CPTP group animals (P<0.05), but none in sham animals (P>0.05).2. Immunohistochemical studies: At the day 14 after surgery, the expression densities of KATP in spinal dorsal horn neurons was decreased significantly both in CCI group and in CPTP group, compared to the sham group respectively (P<0.05).Conclusion:In both models of chronic constriction injury in sciatic nerve pain and chronic postthoracotomy pain, the expression densities of KATP in the membrane of spinal dorsal horn neurons were significantly decreased, compared to the sham group respectively. It is suggested that the change of expresion of KATP channel may play a role in the pathogenesis of allodynia associated with neuropathic pain and chronic postthoracotomy pain, and KATP channel could be a potential therapeutical target for these kinds of pain.