| Part one: Expression of Connexin 43 in Spinal Dorsal Hornof Adjuvant Arthritis RatsObjective To investigate the expression of connexin 43 (Cx43) in spinal dorsal hornof adjuvant arthritis rats. Methods 1) Animal behavior research: 20 rats were randomlydivided into 2 groups: CFA model group and NS control group (n=10). Adjuvant arthritismodel was produced by inoculation of complete Freud's adjuvant (CFA) at outer side ofleft ankle joint. NS control group rats were given hypodermic injection of NS 50μl.Bilateral paw withdrawal thermal latency (PWTL) and paw withdrawal mechanicalthreshold (PWMT) were continually observed during the time course of the model'sdevelopment. 2) Morphological study: 20 male rats were randomly divided into 4 groups: NS control, C2h, C 3d and CTd group (n=5). Immunohistochemical analysis wasrespectively conducted to study the change of Cx43 expression in bilateral lumbar spinaldorsal horn at relevant time post CFA inoculation. Outcomes 1) Unilateral inoculation ofCFA in outer side of the rat anklejoint could induce thermal and mechanical hyperalgesiain injured ipsilateral (P＜0.01) and contralateral (mirror-image) side (P＜0.01 or 0.05) inpost-inoculation 3h～7d. 2) compared with NS control group, the expression of Cx43increased significantly in bilateral spinal dorsal horn after CFA inoculation (P＜0.01 or0.05). Conclusions 1) Unilateral inoculation of CFA induced adjuvant arthritis have asignifiant phenomena of secondary hyperalgesia, including extraterritorial pain andmirror-image pain. 2) The increase of Cx43 expression in lumbar spinal bilateral dorsalhorn of adjuvant arthritis rats suggested gap junction may play an important role inadjuvant arthritis induced pain. Part Two: Antinociceptive Effects of IntrathecalCarbenoxolone on Adjuvant Arthritis RatsObjective To investigate the antinociceptive effects of intrathecal carbenoxolone(CBX), a gap junction blocker, on adjuvant arthritis rats. Methods Chronic lumbarintrathecal catheters were implanted and then confirmed in all rats. 1) At first, thetime-effect and dose-effect relationships between intrathecal CBX and paw withdrawalthermal latency (PWTL) were studied in normal rats. 32 male rats were randomly dividedinto 4 groups: NS control group, CBX 25, CBX 50 and CBX 100 group (n=8). Differentdoses of intrathecal CBX were administrated respectively. Bilateral PWTL werecontinuously measured at 0.5h before drug delivery and 0.5h, 1～8h (per integral point)after drug delivery. 2) Animal behavior research: 40 rats were randomly divided into 5groups. Adjuvant arthritis model was produced by inoculation of complete Freud'sadjuvant (CFA) at outer side of left ankle joint. One group of them was given intrathecalCBX 100μg at 0.5h pre-CFA inoculation as pretreatment. Three doses of CBX (25, 50, 100μg) and NS 10μl were respectively administered in the other 4 groups at 0.5h, 1d, 3d, 5d, 7d, 10d, 14d post-CFA. PWTL was measured at 2h after each drug delivery. Duringthe first day of inoculation, the change of PWTL was especially continually observed. 3)Morphological study: 15 male rats were randomly divided into 3 groups (n=5). NScontrol group rats were given hypodermic injection of NS 50μl at outer side of left anklejoint, whereas others were given CFA 50μl inoculation. 3d later, NS control group andCFA group rats were given intrathecal injection of NS 20μl, and CBX group CBX 100μg(20μl). 2 h after every drug delivery, spinal intumescentia lumbalis were taken to conductc-Fos immunohistochemistry staining analysis and FLIN counting. Results 1) CBXcould increase the threshold of radiant heat-induced pain reversibly anddose-dependently (P＜0.05 or 0.01). The summit effect is at the 2nd hour. 2) CBX couldreverse periphery CFA-induced thermal hyperpalgesia dose-dependently in all phrases, ofinflammatory pain (P＜0.05 or 0.01). Pretreatment of CBX could postpone theappearance of thermal hyperalgesia during the first day (P＜0.01). 3) Expression of c-Fos protein in lumbar spinal bilateral dorsal horn increased significantly at the 3rd day afterCFA injection, with an increase in FLI neurons numbers and size. Intrathecalcarbenoxolone could reverse such change. Compared with CFA groups, the difference isof statistic significance (P＜0.01). Conclusion These findings proved that carbonexolone, as a kind of GJ blocker, has significant antinociceptive effects on adjuvantarthritis-induced pain (including extraterritorial and mirror-image pain), which suggestsgap junction may play an important role in central sensitization of inflammatory pain.
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