The Anxiolytic Effect Of Cedarwood Essential Oil And Its Mechanism

Cupressaceae plants are widely distributed with huge biomass.Although the plants possess significantly ecological and economic benefits,waste material produced in the process of thinning and cutting results in the decreased comprehensive utilization rate of resource.Cedarwood essential oil,mainly extracted from the Cupressaceae plants,is the concentrated aromatic compounds,which has been widely applied in production and life.Anxiety disorder is highly prevalent in the present world,as well as a cardinal symptom of many psychiatric disorders.Several researches have demonstrated that cedrol,a sesquiterpene alcohol substance derived from cedarwood oil,exerts the modulation role to autonomic nervous activity.Nevertheless,there are no systematically scientific studies on the anxiolytic effects and mechanism of cedarwood oil and cedrol.Therefore,the study has a potentially great significance for further utilization of the oil resource and to improve the additional value of plant raw material.According to the greatest abundance of cedrol in essential oils used in the study,certain oil sample was selected from four oil samples.The main objective of the present study was to assess the anxiolytic effect of the selected oil via inhalational and intraperitoneal administration using two anxiety models,elevated plus maze?EPM?and light-dark box?LDB?in ICR mice,respectively.Furthermore,the active constituents of the oil and its putative mechanism of anxiolytic effect was investigated,via behavioral performance in models,neurochemical changes and neurotransmitter signaling transduction.Main results were as follows:1.The essential oils from wood sections of Cupressus funebris Endlicher,Juniperus virginiana L.and Juniperus mexicana Schiede,as well as the leaf of Juniperus virginiana L.,were collected and analyzed by gas chromatography-mass spectrometry?GC-MS?.The compositions of oils from wood in greatest abundance mainly were sesquiterpene alcohol??-cedrol?and sesquiterpenes??-cedrene and cis-thujopsene?.The Juniperus virginiana L.essential oil?Eastern red cedarwood oil,CWO?was selected as the experimental material for its highest abundant cedrol?24.58%?,greater than that in other two cedarwood oils.Inconsistent with CWO,monoterpene alcohol?terpinen-4-ol?,monoterpenes?sabinene,?-terpinene and?-myrcene?followed by ester?bornyl acetate?were mainly observed in the oil from leaves.2.The inhalation administration of CWO and cedrol reduced the anxious behaviors in the animal anxiety models,respectively,but cedrene failed.Quantitative analysis of CWO were developed and validated using a combination of external standard procedure and gas chromatography-flame ionization detector?GC-FID?.The results indicated that the actual content of cedrol and cedrene were 218.20 mg/mL and 242.12 mg/mL,respectively.A test battery of EPM and LDB was used to evaluated the anxiolytic effect of CWO inhalation on male and female mice.Inhalation administration of CWO?2.5%?significantly increased the percentage of entry in the open arms and the percentage of time in the open arms of male mice in the EPM,but not in LDB.However,for the female mice,1%and 7.5%CWO inhalation increased the percentage of time in the open arms in the EPM and the percentage of time in the light chamber in the LDB,respectively.As an indicator of locomotor activity,no significant changes were observed in both tests.Furthermore,we investigated the anxiolytic effects of cedrene and cedrol inhalation.Interestingly,neither anxiolytic effect of cedrene on male and female mice nor significant changes in distance were found.Cedrol inhalation significantly elevated the percentage of time in the light chamber in LDB of males and females.No significant changes in distance in LDB were observed,suggesting that cedrol inhalation possessed an anxiolytic effect in the LDB,without inhibitory effect on locomotor activity.3.The intraperitoneal?i.p.?administration of CWO and cedrol showed a significant anxiolytic effect,respectively,but not cedrene.Female mice intrinsically were less responsive to cedrol.The EPM and LDB tests were applied to evaluated the anxiolytic effects of CWO administration?i.p.?.This work provided strong evidences that CWO could exert a significant anxiolytic effect on males in the EPM and females in the LDB with an increase in distance traveled in EPM and LDB tests,respectively.Cedrene administration?i.p.?produced a similar profile with cedrene inhalation,in which a limitedly significant anxiolytic effect was observed.Cedrol demonstrated an apparently dose-dependent anxiolytic effects in both EPM and LDB tests after i.p.administration,with which female mice intrinsically were less responsive to cedrol.Although the ages of animals used was different,sex differences in sensitivity to cedrol was also been acknowledged in this study,in which cedrol administration?i.p.?produced significant anxiolytic effect on males in both EPM and LDB tests?400-1600 mg/kg and 800-1600 mg/kg,respectively?,as well as increased the distance travelled in apparatuses at 200-1600 mg/kg,whereas,cedrol at dose of 1200-1600 mg/kg significantly increased the parameters of anxiolytic-like activity of females evaluated in both EPM and LDB tests.4.Cedrol could be responsible for the pharmacological effects of CWO.Quantitative analysis of monoamines neurotransmitters and their metabolites in brain region,which are related to the modulation of anxiety,were conducted using liquid chromatography combined with electrochemical detector?LC-ECD?.Both CWO and cedrol significantly affected the contents of 5-hydroxytryptamine?5-HT?and dopamine?DA?in male and female mice.The anxiolytic effect of cedrol might work on the 5-HTnergic and DAnergic pathways through affecting the response to DAnergic activity by modulating the 5-HTnergic system.5.Cedrol administration?i.p.?might possess an anxiolytic effect without sedative effect.The sedative effect of cedrol?1200 mg/kg,i.p.?was evaluated based on pentobarbital-induced sleep experiment.Diazepam?2 mg/kg,i.p.?significantly shortened the sleeping latency,and prolonged the sleeping time induced by pentobarbital sodium.Compared with the control,the sleeping latency was shortened by cedrol,but greater than that of diazepam?DZP?treatment.On the contrary,compared with control,the sleeping time was also shortened after cedrol administration.6.The dopaminergic systems,especially the D₁ receptor pathway,was associated with the anxiolytic-like effect of cedrol administration?i.p.?.The putative mechanism of the anxiolytic effect of cedrol was investigated via neurotransmitter receptor antagonist-induced experimental models.The anxiolytic effect of cedrol were not antagonized by WAY100635(5-HT_1AA receptor antagonist),flumazenil?GABA_A receptor antagonist?,suggesting that the anxiolytic-like effect of cedrol seemed to be not directly associated with either serotonergic or GABAergic system.Furthermore,the anxiolytic-like effects and locomotor activity induced by cedrol were abolished by SCH23390?dopamine D₁ receptor antagonist?,but not sulpiride?dopamine D₂/D₃receptor antagonist?.The neurochemical evaluation in brain regions was conducted using high-performance liquid chromatography-fluorescence detector?HPLC-FLD?.Cedrol?1200 mg/kg,i.p.?significantly decreased the levels of DA and NE in hippocampus,striatum and hypothalamus,whereas,no significant change was observed in the 5-HT level,indicating that the dopaminergic system was associated with the anxiolytic effect of cedrol.Sole administration of SCH23390?0.125 mg/kg,i.p.?also significantly reduced the contents of DA and 5-HT in the hippocampus and hypothalamus of mice;co-administration of SCH23390 and cedrol further reduced the levels of DA and5-HT in the hypothalamus.