| Objective:To establish modified rat model of nicotine dependence-withdrawal syndrome by subcutaneous injection of nicotine.Methods:30SD rats were randomly divided into5groups,6rats per group, including Control group, normal saline group (NS group), nicotine3mg/kg/d group (NT3group), nicotine9mg/kg/d group (NT9group) and nicotine18mg/kg/d group (NT18group). Each group received no injection, subcutaneous injection of normal saline, nicotine1mg/kg,3mg/kg and6mg/kg respectively three times a day for seven days. At60min after the last injection of nicotine, subcutaneous injection of mecamylamine lmg/kg was given for each rat. Weight changes of rat during injections of nicotine and after nicotine withdrawal, survival rate and its withdrawal symptoms score were recorded.Results:Compared with NT3group, on the seventh day after injection of nicotine, weight gain of the rats was significantly slow in NT9group and NT18group (3.8±1.3g,2±0.3g vs7.2±1.0g)(P<0.05); On the first and the second withdrawal day, weight gain of the rats was significantly rapid in NT9group and NT18group (P<0.01). Compared with NT3group, the rats in NT9group and NT18group had significant more withdrawal symptoms after mecamylamine precipitation (P<0.01). The incidence of mortality in NT18group was17%.Conclusion:By continuous subcutaneous injection of nicotine9mg/kg/d for seven days, modified rat model of nicotine dependence-withdrawal syndrome can be successfully established. Objective:To observe the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of foot plantar in rats after nicotine withdrawal and incisional rats with nicotine withdrawal.Methods:30SD rats were randomly divided into5groups,6rats in each group.①Control group:the rats were fed in normal conditions for7days, no any treatment;②NS group:after normal feeding the rats were given subcutaneous injection of normal saline0.1ml, three times a day at daily5:00,13:00and21:00for7days;③NT group: after normal feeding the rats were given subcutaneous injection of nicotine3mg/kg, three times a day at three time points above for7days;④IP group:after normal feeding for7days the rats underwent incisional pain model at right hind foot plantar according to Brennan method;⑤NT+IP group:after normal feeding the rats were given subcutaneous injection of nicotine3mg/kg, three times a day at three time points above for7days. On the7th day the rats underwent incisional pain model at right hind foot plantar. On the8th day the rats in NS group, Control group and NT group received measurement of MWT and TWL in the right hind foot plantar for7days. The rats in IP group and NT+IP group received measurement of MWT and TWL in bilateral lower extremity foot for7days.Results:1. Effect of nicotine withdrawal on pain behaviors in rats(1) Effect of nicotine withdrawal on MWT in ratsCompared with Control group, MWT in NT group had significantly decreased from the first day to the7th day after nicotine withdrawal (P<0.01); Within the NT group, the MWT reduced more significantly on the first and second day (P<0.01).(2) Effect of nicotine withdrawal on TWL in rats Compared with Control group, TWL in NT group had significantly decreased from the first day to the7th day after nicotine withdrawal (P<0.01); Within the NT group, the TWL reduced more significantly on the4th day (P<0.01).2. Effect of nicotine withdrawal on pain behaviors in incisional rats(1) Effect of nicotine withdrawal on MWT in incisional ratsCompared with the operative side plantar MWT in the IP group, the operative side plantar MWT in the IP+NT group was significantly lower on postoperative daysl-7respectively (P<0.05) and the healthy side plantar MWT in the IP group was significantly higher on postoperative days1-4respectively (P<0.05), with no significant difference in postoperative days5-7(P>0.05). Compared with the healthy side plantar MWT in the IP group, the healthy side plantar MWT in the IP+NT group was significantly reduced on postoperative days1-7respectively (P<0.05).(2) Effect of nicotine withdrawal on TWL in incisional ratsCompared with the operative side in the IP group, the operative side plantar TWL in the IP+NT group was significantly lower on daysl-7respectively (P<0.05) and the healthy plantar TWL in the IP group was significantly higher on daysl-6(P<0.05). Compared with the healthy side plantar TWL in the IP group, the healthy plantar TWL in the IP+NT group was significantly reduced on days1,2,3,5and6(P<0.05). Objective:To study the function of spinal microglia in postoperative hyperalgesia in incisional rats with nicotine abstinence.Method:42SD rats were randomly divided into3groups.①IP Group (n=18):According to the executed time IP group is divided into3sub-groups, six rats in each group. Rats received normal feeding and underwent incision pain model at right hind foot plantar. MWT and TWL were determined on the first, second, third,5th and7th day after surgery.②NT+IP Group(n=18):According to the executed time NT+IP Group is divided into3sub-groups, six rats in each group. After normal feeding the rats were given subcutaneous injection of nicotine3mg/kg, three times a day at daily5:00,13:00and21:00for7days. On the7th day the rats underwent incisional pain model at right hind foot plantar. MWT and TWL were determined on the first, second, third,5th and7th day after surgery.③M group(n=6):According to NT+IP Group, the rats were given intraperitoneal injections of minocycline100mg/kg one hour before surgery. Then MWT and TWL were determined on the first, second, third,5th and7th day after surgery. On the first,3th and7th the rats were executed and the lumbar enlargement of spinal cord L4-6were collected. IBA-1positive cells were determined by immunohistochemical method.Results:1. Effect of intraperitoneal minocycline on pain behaviors in incisional rats with nicotine withdrawal (1) Compared with IP group, MWT in NT+IP group was significantly reduced on1d,2d,3d,5d, and7d after surgery (P<0.01). Compared with NT+IPgroup, MWT in M group was significantly increased on the first day after surgery (P<0.01). But there was no difference at2d,3d,5d, and7d after surgery(P>0.05).(2) Compared with IP group, TWL in NT+IP group was significantly reduced on1d,2d,3d,5d, and7d after surgery (P<0.01). Compared with NT+IPgroup, TWL in M group was significantly increased on the first day after surgery (P<0.01). But there was no difference at2d,3d,5d, and7d after surgery (P>0.05).2. Changes of IBA-1-positive cells in two groupsBy immunohistochemical method IBA-1positive cells presented brown marker. Within the group, the number of IBA-1-positive cells in spinal dorsal in IP group was significantly increased on the third postoperative day than those of1d and7d after surgery (P<0.01). Compare with IP Group, the number of IBA-1-positive cells in NT+IP group increased significantly (P<0.01), and also increased at the3d and7d after surgery (P<0.01).Conclusion:Nicotine exposure can activate spinal microglia. Spinal microglia contributes to postoperative hyperalgesia in incisional rats with nicotine abstinence. Objective:To study the function of IL-1β in the surrounding incision tissue in postoperative hyperalgesia in incisional rats with nicotine withdrawal.Method:96SD rats were randomly divided into4groups:①Naive group(n=6):Rats were fed under normal conditions, not doing anything;②NT group(n=30):After normal feeding the rats were given subcutaneous injection of nicotine3mg/kg, three times a day at daily5:00,13:00and21:00for7days;③IP group(n=30):After normal feeding for7days the rats underwent incisional pain model at right hind foot plantar according to Brennan method;④NT+IP Group(n=30):After normal feeding the rats were given subcutaneous injection of nicotine3mg/kg, three times a day at daily5:00,13:00and21:00for7days. On the7th day the rats underwent incisional pain model at right hind foot plantar. The rats in NT groups, IP group and NT+IP Group were divided into5sub-groups by preoperative2h, postoperative2h,24h,48h and72h, six in each sub-group. MWT and TWL were determined at postoperative2h,24h,48h and72h. Incision tissue was collected at preoperative2h, postoperative2h,24h,48h and72h for measurement of IL-1Beta.Results:1. Pain behaviors in incsional rats with nicotine withdrawal(1) Foot plantar MWT in incsional rats with nicotine withdrawalCompared with Naive group, MWT in IP group started to decline from postoperative2h (P<0.05) in rats, to the minimum at postoperative48h (P<0.01) and began to improve at postoperative72h. Compared with IP Group, MWT in NT+IP group significantly reduced at postoperative2h,24h,48h and72h (P<0.05). MWT at postoperative48h was the most significant (P<0.01).(2) Foot plantar TWL in incsional rats with nicotine withdrawalCompared with Naive group, TWL in IP group started to decline from postoperative2h (P<0.05) in rats, to the minimum at postoperative48h (P<0.01) and began to improve at postoperative72h. Compared with IP Group, TWL in NT+IP group significantly reduced at postoperative2h,24h,48h and72h (P<0.05). TWL at postoperative48h was the most significant (P<0.01).2. Postoperative changes of IL-1β in the surrounding incision tissue in incisional rats with nicotine withdrawal.Compared with preoperative2h in IP group(11.52±0.35pg/mg), IL-1β level in NT group at all the time points significantly increased (P<0.01). IL-1β level in IP Group at preoperative2h (44.28±6.27pg/mg) began to rise, to peak at postoperative48h (111.83±8.24pg/mg), began to drop at postoperative72h.Compare with IP group for each time point, IL-1β level in NT+IP group was significantly increased (P<0.01).Within NT+IP group, compared with preoperative2h (19.69±1.86pg/mg), IL-1β level at all the time points significantly increased (P<0.01). IL-1β level began to rise at preoperative2h (62.18±3.74pg/mg), to peak at postoperative48h (129.47±6.26pg/mg), began to drop at postoperative72h.Conclusions:1. Nicotine withdrawal may cause postoperative hyperalgesia in incisional rats with postoperative48h as the most significant. 2. Nicotine dependence-withdrawal can cause IL-1β levels rise in the in the surrounding incision tissue. IL-1β was involved in postoperative hyperalgesia in incsional rats with nicotine abstinence. |
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