RESUMO
Objective To evaluate the effect of dexmedetomidine on the long-term sensorimotor gating system after sevoflurane anaesthesia in neonatal rats.Methods One hundred forty-four clean-grade healthy male Sprague-Dawley rats,aged 4-6 days,weighing 8-15 g,were divided into 4 groups (n =36 each) using a random number table method:control group (group C),sevofluraue group (group S),dexmedetomidine plus sevoflurane group (group D + S),and dexmedetomidine plus α2 receptor antagonist atipamezole plus sevoflurane group (group D+A+S).In group S,anesthesia was induced with 6％ sevofluraue for 3 min and maintained with 2.1％ sevoflurane,and the anesthesia time was 6 h in total.Dexmedetomidine 25 μg/kg was intraperitoneally injected in group D.In group D +A+ S,dexmedetomidine 25 μg/kg and atipamezole 250 μg/kg were intraperitoneally injected,and the other treatments were similar to those previously described in group S.Twelve rats in each group were randomly selected after anesthesia and sacrificed,and blood samples were collected for determination of serum corticosterone concentrations by enzyme-linked immunosorbent assay.Twenty-four rats were randomly selected in each group,and prepulse inhibition (PPI) of startle test was performed at 70 days after birth.PPI rate (PP3％,PP6％,PP12％) was calculated.The serum corticosterone concentration was measured by restraint stress test on 80 days after birth.Results There was no significant difference in PP6％ or PP12％ among the four groups (P＞0.05).Compared with group C,PP3％ was significantly decreased,and the serum corticosterone concentration was increased after the end of anesthesia and during restraint stress test at 80 days after birth in S and D+A+ S groups (P＜0.05),and no significant change was found in the parameters mentioned above in group D (P＞0.05).Compared with group S,PP3％ was significantly increased,and the serum corticosterone concentration was decreased after the end of anesthesia and during restraint stress test at 80 days after birth in group D (P＜0.05),and no significant change was found in the parameters mentioned above in group D+ A+S (P＞0.05).Compared with group D,PP3％ was significantly decreased,and the serum corticosterone concentration was increased after the end of anesthesia and during restraint stress test at 80 days after birth in group D+A+S (P＜0.05).Conclusion Dexmedetomidine can alleviate the damage to long-term sensorimotor gating system after sevoflurane anesthesia in neonatal rats,and the mechanism may be related to activating central α2 receptors and improving hypothalamic-pituitary-adrenal axis hyperfunction.
RESUMO
OBJECTIVE To analyze impulsive-like behaviors of SD rats induced by pramipexole in Y-maze avoidance tasks. METHODS Behaviors of SD rats in Y-maze avoidance tasks were recorded with a camera and analyzed by Noldus Etho Vision XT8 software after acute subcutaneous injection of pramipexole(0.1,1 and 10 mg · kg-1),including right reaction numbers of 20 consecutive avoidance tasks,shuttle number of times between the three arms of Y-maze, distance covered in Y-maze and time spent in safe arms during 20 consecutive avoidance tasks. Then,the prepulse inhibition(PPI)of the startle reflex test was used to assess the effect of pramipexole on sensorimotor gating (SG). Effects of pramipexole on the dialyzed content of monoamine neurotransmitter and its metabolites in the striatum and amygdala of SD rats were measured by microdialysis in vivo. RESULTS Compared with normal control group,the rats of pramipexole group showed a significant increase in the shuttle number of times and distance covered in Y-maze between Y-maze avoidance tasks(P<0.01),but a statistically significant decrease in the time spent in safe arms(P<0.01),while the number of right reactions in Y-maze avoidance tasks was not changed. Such premature responses were quite similar to certain impulsive-compulsive behaviors in rodent models,such as five-choice serial reaction time tasks. In the PPI test,pramipexole displayed an impairing effect on SG(P<0.01). The microdialysis results showed that there was an increase of dopamine and 5-hydroxytryptamine in the striatum of pramipexole group, but not statistically significant. Monoamine neurotransmitters and their metabolites were not significantly changed in the amygdala. CONCLUSION Pramipexole can induce impulsive-compulsive behaviors in Y-maze avoidance tasks,which might be attributed to impaired SG.