Role of Stargazin in trafficking of GluRl-containing AMPA receptors from cytoplasm to cell membrane in spinal dorsal horn in rats with incisional pain

Abstract

Objective To evaluate the role of Stargazin in trafficking of GluR1-containing AMPA receptors from cytoplasm to cell membrane in the spinal dorsal horn in rats with incisional pain.Methods Forty-five adult male Sprague-Dawley rats,aged 6-8 yr,weighing 280-300 g,were randomly divided into 5 groups (n =9 each):control group (group C),sham operation group (group S),incisional pain + normal saline group (group P),incisional pain + Stargazin small interference RNA (siRNA) group (group Ⅰ),and incisional pain + non-sense siRNA group (group N).In P,I and N groups,normal saline 10 μl,20 μmol/L siRNA and 20 μmol/L non-siRNA 10 μl were injected intrathecally,respectively,twice a day for 3 consecutive days.A 1 cm long incision was made in the plantar surface of right hindpaw.Cumulative pain score (CPS) and paw-withdrawal threshold to yon Frey stimuli (PWT) were measured at 3 h after incision.The animals were sacrificed after pain behavior assessment.Their lumbar segments of the spinal cord (L3-6) were removed.The expression of GluR1 and GluR2 in cell membrane and cytoplasm in spinal cord dorsal horn was determined by Western blot analysis.The co-expression of Stargazin with GluR1 and GluR2 in the spinal dorsal horn was examined by co-immuno-precipitation.Results Compared with group C,the CPS was significantly increased,the PWT was decreased,the expression of GluR1 in cytoplasm was down-regulated and the expression of GluR1 in cell membrane was up-regulated in N and P groups,and the CPS was increasedin group Ⅰ (P ＜ 0.05 or 0.01).Compared with group P,the CPS was significantly decreased,the PWT was increased,the expression of GluR1 in cytoplasm was up-regulated,the expression of GluR1 in cell membrane was down-regulated,and the expression of Stargazin and co-expression of Stargazin with GluR1 and GluR2 in the spinal dorsal horn was down-regulated in group Ⅰ (P ＜ 0.05 or 0.01).Conclusion Stargazin mediates trafficking of GluR1-containing AMPA receptors from cytoplasm to cell membrane in spinal dorsal horn and is involved in the development of hyperalgesia in rats with incisional pain. Key words: Receptors, AMPA; Protein transport; Pain; Spinal cord; Stargazin