Effect Of Median Nerve Electrical Stimulation On Expression Of GABAb Receptor In Prefrontal Cortex Of Traumatic Brain Injury Induced Comatose Rats

Objective:To investigate the changes of GABAb receptor(GABAb R)expression and the relationship with Orexin system in prefrontal cortex of traumatic brain injury(TBI)induced comatose rats after median nerve electrical stimulation(MNS).And to preliminarily explore the effect and possible mechanisms of median nerve electrical stimulation in wake-promoting.To explore whether Orexin system exerts its ‘switch’effect in wake-promoting after TBI or not.Methods:Sprague Dawley rats were divided into 4 groups(n=120): control group,shamstimulation group,MNS group and Orexin1 receptor(OX1R)antagonist group.We applied MNS to rats which were comatose after ‘Free-fall drop model ’and observed behaviours then prefrontal cortex(PFC)was extracted of each group at 6h,12 h,24h after the experiment.Western-blot techniques and immunohistochemistry were used to detect the expressions of GABAb R.Results:Rats by "Free-fall drop model " appeared behavioral changes similar to clinical coma,while after MNS,the comatose rats showed a transient behavioral arousal.The states of consciousness in control group were class I for all,in sham-stimulation group were class 5.33 ± 0.758,stimulation group 3.80 ± 1.064,antagonist group 4.67 ±0.844.The consciousness grade for four groups was " control < stimulation<antagonist <sham-stimulation ",there was statistical significance between the four groups(P<0.05).The results of western-blot showed that the expression of GABAb R in prefrontal cortex in the four groups was “6h<12h<24h”,there was no statistical significance in control group and stimulation group(P > 0.05),while there was statistical significance in sham-stimulation group and antagonist group(P<0.05).There was an increasing trend in MNS,control,antagonist and sham stimulation group in comparisons among four groups,differences had no statistical significance between control group and MNS group(P > 0.05),while,there was statistical significance between the rest every two groups(P < 0.05).The results of immunohistochemistry showed that there was an enhancing trend in 6h,12 h and 24 h,differences had statistical significance among the four groups.There was an increasing trend in MNS,control,antagonist and sham stimulation group,differences had statistical significance among the four groups.Conclusion:MNS has an effect on arousal by down-regulating GABAb R in prefrontal cortex of TBI induced comatose rats.Orexin system may exert its ‘switch’ effect in wake-promoting after TBI by regulating the expression of GABAbR.