Neuronal Mechanisms Of Borneol In The Treatment Of Impaired Awake Activity By Long-term Continous Operations

Long-term continous operations are becoming more popular in the modern society, including the long-distance drives,the continual military operations and so on.It is well known that these ultra dilirnal periods work as well as compulsory work without enough sleep have serious influences on operator's capacity and cognitive function,which usually reduces the working efficiency.How to improve the long-term continuous operation personnel's working efficiency is an important issue which shoule be urgently solved in the modern medical research field.The research has already been carried out in our laboratory. Rat model was established by using a treadmill protocol.Rats were allowed to do continous exercise for 48 h in the conventional treadmill equipment used for small animal.It is suggested that rats' awake activity and cognitive function could be apparently impaired by stimulating many kinds of complicated environment in long-term continuos operations.Our research indicated that Borneol could reverse the deleterious effects of long-term continuous operations on awake activity,but the neuronal mechanisms of Borneol are not illustrated.In the present study,effects of Borneol on single-unit activity in the prefrontal cortex and its neuronal mechanisms are firstly studied.Subsequently,to investigate its neuronal mechanisms,we examined the expression of orexin-A and c-Fos in the lateral hypothalamic area of rat after long-term contious operations and Borneol applied.1.Effects of Borneol on single-unit activity in prefrontal cortex of rats and its mechanisms(1) Excitory effects of Borneol on PFC of ratsThe excitability of cortex was judged by the frequency of neuron discharge in the prefrontal cortex.Three types of firing patterns were exhibited in neuron:single and irregular discharges,cluster discharges and complex discharges,with a mean frequency of 7.45±1.67 Hz(n=48) and duration of 3～3.5 ms.The mean frequency of unit discharges was gradually increased after application of the middle and high dosages of Borneol(1.2g/5ml/k and 2.0g/5ml/kg) by the placed gastric tube,which reached to a peak level at 20 to 25 minutes(n=12,P＜0.05;n=12,P＜0.01 ).The degree of increase induced by the high dosage of Borneol was more sigficicant than that of middle(n=12,P＜0.01).While no obvious difference was observed after application of Borneol at low dose.These data show the excitatory effects of Borneol on single-unit activity with a dose-dependent manner.The improvement of Borneol on the impaired awake activity of rats is probably related to the increased single-unit activity in the prefrontal cortex.(2) Neuronal mechanisms of excitatory effects of Borneol on prefrontal cortexâ‘ H₁ histamine antagonist pyrilamine prevented the excitatory effects of Borneol on unit discharges of prefrontal cortex neuronsThe mean frequency of unit discharge of prefrontal cortex was gradually decreased after i.c.v,application of 60μg H₁ histamine antagonist pyrilamine(n=12,P＜0.05 ).And in the presence of pretreatment 60μg pyrilamine,the high dosage of Borneol failed to exert an excitatory action on unit discharges of cortical neurons(n=12,P＞0.05 ).These results indicate that the excitatory effects of Borneol on the neurons of prefrontal cortex may be mediated by activation of histaminergie neurotransmission.②α1-adrenoreceptor antagonist prazosin had a few contributions on the effects of Borneol on unit discharges of prefrontal neuronsThe mean frequency of unit discharge of prefrontal cortex showed no evident difference after i.c.v,application ofα1-adrenoreceptor antagonist prazosin at the dose of 63μg(n=12,P＞0.05 ).And in the presence of pretreatment 63μg prazosin,application of the high dosage of Borneol was administered by the placed gastric tube and increase the mean frequency(n=12,P＜0.05 ),but it is still lower than that only application of the high dosage of Borneol significantly(n=12,P＜0.05).Therefore,these results suggest that Borneol induced-discharge activities may be partly blocked by prazosin at the dose of 63μg, and these excitatory effects appear to be partly associated with noradrenaline neurotransmission.â‘¢5-serotonin selective receptor antagonist(5-HT₂) ritanserin showed little influence on the effects of Borneol on unit discharges of prefrontal cortex neuronsThe mean frequency of unit discharge of prefrontal cortex was gradually decreased after i.c.v,application of 5-HT₂ antagonist ritanserin at the dose of 40μg(n=12,P＜0.05). And in the presence of pretreatment 40μg ritanserin,application of the high dosage of Borneol was administered and increased the mean frequency(n=12,P＜0.05),but it is still lower than that only application of the high dosage of Borneol significantly(n=12,P＜0.05).Therefore,these results suggest that Borneol induced-discharge activities may be partly blocked by ritanserin at the dose of 40μg,and these excitatory effects appear to be partly associated with serotonin neurotransmission.2.Effects of Borneol on levels of nerurotransmitters in prefrontal cortex(PFC) after long-term continous operations(1) Effects of long-term continous operations on nerurotransmittors in PFCIn the present study,the levels of NA,DA and 5-HT in prefrontal cortex of rats were determined after long-term continous operations by high performance liquid chromatography combined with electrochemical detection(HPLC-ECD).Our results indicated that the levels of NA decreased significantly as compared to control group (P＜0.05),but the level of DA and 5-HT did not change(P＞0.05).Therefore,these data imply that the depressed awake activity and cognitive function induced by long-term continous operations appear to be associated with noradrenergic modulation.(2) Effects of Borneol on levels of neurotransmitters in prefrontal cortex(PFC) after long-term continous operationsBorneol was applied to the operating rats after long-term continous operations by gastric tube,and the control animals were treated with vehicle.The levels of these neurotramsmitters in PFC were determined by HPLC-ECD.To the operational group,the levels of noradrenaline and 5-serotonin in PFC increased significantly after application of borneol(n=5,P＜0.05),but dopamine not.The results indicate that the improvements of borneol are associated with the increase in noradrenaline and 5-serotonin levels in PFC.3.Effects of Borneol on expression of orexin-A and c-Fos in LHA in rats after long-term continuous operations(1) Using a rat model of long-term continuous oPerations to investigate the effects of long-term continuous operations on orexin-A and c-Fos in LHA.We found the number of orexin-A immunoreactive neurons and c-Fos in LHA significantly decreased as compared with the control group.The results indicate that the depressesd awake activity and cognitive function appear to be associated with the decreased expression of orexin-A and c-Fos.(2) Borneol was administered by the placed gastric tube.We observed the effects of Borneol on the expression of orexin-A and c-Fos in the long-term continuous rat model..We found the number of orexin-A immunoreactive neurons and c-Fos in LHA significantly increased compared with the control group.The results indicate that the improvement of borneol are associated with the increased expression of orexin-A and c-Fos.In summary,the improvement of borneol on impaired awake activity and cognitive function is probably associated with its excitatory effects on PFC,as well as the increased level of noradrenaline and 5-serotonin and increased expression of orexin-A and c-Fos in LHA.