The 5-HT2c receptor gene Cys23Ser polymorphism influences the intravaginal ejaculation latency time in Dutch Caucasian men with lifelong premature ejaculation

It has been postulated that the persistent short intravaginal ejaculation latency time （IELT） of men with lifelong premature ejaculation （LPE） is related to 5-hydroxytryptamine （HT）2c receptor functioning. The aim of this study was to investigate the relationship of Cys23Ser 5-HT2c receptor gene polymorphism and the duration of IELT in men with LPE. Therefore, a prospective study was conducted in 64 Dutch Caucasian men with LPE. Baseline IELT during coitus was assessed by stopwatch over a 1-month period. All men were genotyped for Cys23Ser 5-HT2c receptor gene polymorphism. Allele frequencies and genotypes of Cys and Ser variants of 5-HT2c receptor gene polymorphism were determined. Association between Cys/Cys and Ser/Ser genotypes and the natural logarithm of the IELT in men with LPE were.investigated. As a result, the geometric mean, median and natural mean IELT were 25.2, 27.0, 33.9s, respectively. Of all men, 20.0%, 10.8%, 23.1% and 41.5% ejaculated within 10, 10-20, 20-30 and 30-60s after vaginal penetration. Of the 64 men, the Cys/Cys and Ser/Ser genotype frequency for the Cys23Ser polymorphism of the 5-HT2c receptor gene was 81% and 19%, respectively. The geometric mean IELT of the wildtypes （Cys/Cys） is significantly lower （22.6s; 95% CI 18.3-27.8s） than in male homozygous mutants （Ser/Ser） （40.4s; 95% CI 20.3-80.4s） （P = 0.03）. It is concluded that Cys23Ser 5-HT2c receptor gene polymorphism is associated with the IELT in men with LPE. Men with Cys/Cys genotype have shorter IELTs than men with Ser/Ser genotypes.

Augmentative effect of tetrandrine on pentobarbital hypnosis mediated by 5-HT_(1A) and 5-HT_(2A/2C) receptors in mice

It has been reported that augmentative effect of tetrandrine on pentobarbital hypnosis in mice may be related to serotonergic system. The present study was undertaken to investigate the interaction of tetrandrine and different 5-HT receptors on pentobarbital-induced sleep by using the loss-of-righting reflex method. The results showed that augmentative effect of tetrandrine on pentobarbital hypnosis in mice were potentiated by the p-MPPI （5-HT1A receptor antagonist） （1 mg/kg, i.p.） and ketanserin （5-HT2A/2C receptor antagonist） （1.5 mg/kg, i.p.）, respectively. Pretreatment with either 8-OH-DPAT （5-HT1A receptor agonist） （0.1 mg/kg, s.c.） or DOI （5-HT2A/2C receptor agonist） （0.2 mg/kg, i.p.） significantly decreased pentobarbital-induced sleep time, and tetrandrine （60 mg/kg, i.g.） significantly reversed this effect. These results suggest that both the 5-HTLA and 5-HT2A/2C subfamily may be involved in the potentiating mechanism of tetrandrine＇s effects on pantobarbital hypnosis.

Roles of 5-HT2 receptors in effects of DOM,ketamine and methamphetamine on prepulse inhibition in Sprague Dawley rats

OBJECTIVE Prepulse inhibition(PPI)of the acoustic startle response provides a measure of sensorimotor gating system mecha⁃nisms,which is known to be impaired in schizo⁃phrenia patients.We assessed the effects of the 5-HT2A/2C receptor agonist(±)2,5-dimethoxy-4-methylamphetamine(DOM),the NMDA receptor antagonist ketamine,the dopamine receptor ago⁃nist methamphetamine(Meth)on PPI and the startle magnitude in SD rats.METHODS AND RESULTS Systemic administration of the three compounds all dose-dependently reduced PPI.However,as far as startle magnitude,only DOM at the doses of 3 mg·kg-1 reduced that,while both ketamine and Meth did not change the startle magnitudes.Furthermore,to determine whether 5-HT2A receptor mediate this effect,the non-spe⁃cific 5-HT2 receptor antagonist cyproheptadine,specific 5-HT2A receptor antagonist ketanserin and specific 5-HT2C receptor antagonist SB242084 were tested.Cyproheptadine,ketan⁃serin and SB242084 did not alter startle ampli⁃tude by themselves in SD rats and only ketanserin slightly increased PPI at higher dose(3 mg·kg-1).PPI impairment induced by DOM was restored by pretreatment of cyproheptadine(1 mg·kg-1)and ketanserin(1 mg·kg-1),while not by pretreat⁃ment of SB242084(1 mg·kg-1).Damage of PPI induced by ketamine and Meth was not reversed by cyproheptadine(1 and 5 mg·kg-1).CONCLU⁃SION The receptor mechanisms underlying the disruption of PPI caused by DOM,ketamine and Meth were different from each other,at least 5-HT2A receptor was not the junction receptor for which the three chemicals acted.

Effects of Estradiol on 5-HTsA and 5-HT2c Receptor Immunolabeling in Rat Hippocampus

Steroid hormones participate in the modulation of serotonergic transmission, including the regulation of synthetic and metabolic enzyme production, as well as receptor and transporter activity. The changes of 5-HT5A and 5-HT2c immunolabeling induced by steroids in the hippocampus ofovariectomized rats were studied in this work. Densitometric analysis in rat hippocampi were carried out for adjacent brain coronal immunolabeled sections after treatment with subcutaneous injections of vehicle, estradiol, progesterone or the combination of both steroids in ovariectomized rats. Exposure to estradiol and the combination of estradiol and progesterone significantly reduced the 5-HT5A-like immunosignal in the CA 1 region while progesterone did not induce changes. On the other hand, exposure to the combination of estradiol and progesterone or estradiol alone increased the 5-HT2c immunosignal in the same region. These results indicate that estradiol is involved in the discrete regulation of serotonin receptors 5-HT5A and 5-HT2c in rat hippocampus.

单相抑郁症中5-HT2A受体基因及MAOA型基因的相互影响

目的探讨单相抑郁症病因中５－ＨＴ２Ａ受体基因与ＭＡＯＡ型基因的相互影响。方法在７２例单相抑郁症患者和８１例正常健康人中，采用ＰＣＲ－ＲＦＬＰ和Ａｍｐ－ＦＬＰ技术检测５－ＨＴ２Ａ和ＭＡＯＡ型的等位基因和基因型分布。结果单相抑郁症与５－ＨＴ２Ａ基因间无遗传关联，但是具５－ＨＴ２Ａ的Ａ２／Ａ２基因型患者与ＭＡＯＡ型的１１４ｂｐ等位基因呈强烈关联（ＲＲ＝６．２５，Ｐ＜００５）。结论５－ＨＴ２Ａ受体基因和ＭＡＯＡ型基因在单相抑郁症发生中可能起有一定相互作用。

Role of 5-HT2A Receptors in Immunomodulation in Animal Models of Aggressive Behavior

Serotonin 5-HT2A receptors are playing an important role in the pathophysiology of aggressive behaviors and in the control of immune function. In the present study, we analyzed the effects of activation and blockade of 5-HT2A receptors with selective ligands on the immune response formation in animals with aggressive behaviors induced by genetic factors (rats selected for the increased aggressiveness toward human) or by chronic social stress (mice of the CBA/Lac strain engaged in 10 days of social confrontations). Activation of 5-HT2A receptors with DOI at 1.0 mg/kg reduced the immune response level both in aggressive rats and mice compared to the corresponding vehicle-treated groups, while DOI administration did not alter the immune reaction in nonaggressive animals. The blockade of 5-HT2A receptors with ketanserin at 1.0 mg/kg resulted in immunostimulation both in mice of the CBA strain not subjected to social stress (the controls) and in nonaggressive rats selected for elimination of aggressiveness. On the other hand, its administration to CBA mice demonstrating offensive aggression enhanced the immune reaction, while the same dose of ketanserin did not modify the immune response level in rats with genetic predisposition to the increased defensive aggression. Thus, our data suggest that the role of 5-HT2A receptors in immunomodulation depends on the specific type of aggression that may be taking into account in the treatment of some neuropsychiatric disorders with the antipsychotic drugs and antidepressants targeting 5-HT2A receptors.

5-HT_(2A)受体基因1438A/G多态性与海洛因依赖的关系

目的··:探讨5 -HT2A 受体基因多态性与海洛因依赖易感性的关系。方法··:用聚合酶链式反应 (PCR)技术结合限制性片段长度多态性 (RFLP)分析技术 ,检测了99名海洛因依赖者和80名正常对照者5 -HT2A 受体基因1438A/G多态性的基因型和等位基因频率。结果··:海洛因依赖者5 -HT2A 受体基因1438A/G多态性基因型A1/A2的频率较对照组高。结论··:5 -HT2A

5-HT_(2A)受体基因-1438G/A多态性与情感障碍的关联研究

目的探索5-羟色胺2A(5-HT_(2A))受体基因启动子区-1438G/A多态性与情感性障碍易感性的关系。方法采用限制性片断长度多态性(RFLP)分析技术,检测情感性障碍和正常对照组的5-HT_(2A)受体基因-1438G/A多态性的基因型和等位基因频率,并根据Hardy-Weinberg遗传平衡法则,比较相互之间的区别。结果1.抑郁症5-HT_(2A)受体基因-1438G/A多态性基因型A1/A1频率(58.51%)较正常对照组(42.86%)高,差异有显著性(2=3.929,P<0.05);2.伴有自杀企图或行为的情感性障碍患者5-HT_(2A)受体基因-1438G/A多态性基因型A1/A2的频率(25.45%)较正常对照组(38.46%)偏低,差异有显著性(2=4.74,P<0.05)。结论5-HT_(2A)受体基因-1438G/A多态性与抑郁症特别是具有自杀企图或行为的患者关联,提示该受体基因多态性可能是抑郁症的易感因子。

精神分裂症患者5-HT2A受体基因相关因素的研究

目的 分析汉族人 5 HT2A受体基因与精神分裂症易感性之间的关系以及影响患者 5 HT2A受体基因的相关因素。方法 2 6 9例精神分裂症病人 ,310例正常对照 ,用聚合酶链式反应 (PCR)扩增及限制性片段长度多态性 (RFLPs)技术测定其 5 HT2A受体基因型和等位基因。结果 发现含 5 HT2A受体基因的等位基因A2的精神分裂症患者平均发病年龄明显大于含等位基因A1的患者 ,但 5 HT2A受体基因与精神分裂症的易感性、患者的性别、家族史、症状严重度均无显著相关。结论 5 HT2A受体基因的等位基因A2可明显推迟精神分裂症患者的发病年龄 ,但 5 HT2A受体基因不影响汉族人精神分裂症的易感性、患者的症状严重度 ,患者 5 HT2A受体基因的频率分布也不受患者的性别。

5-HT2a受体基因T102C多态性与氯氮平疗效的关联分析

探讨５－ＨＴ２ａ受体基因Ｔ１０２Ｃ多态性与氯氮平疗效之间的关系。方法随机抽取了６４例住院的精神分裂症患者和５６例难治性精神分裂症患者作研究，分别给予氯氮平≥２００ｍｇ／ｄ、≥４００ｍｇ／ｄ治疗两个月，用ＰＡＮＳＳ量表评定氯氮平疗效，用限制性片段长度多态性（ＲＦＬＰｓ）技术测定所研究对象的基因型和等位基因。结果发现氯氮平疗效好与难治性精神分裂症患者的含Ａ２的基因型及Ａ２等位基因相关联。结论５－ＨＴ２ａ受体基因Ｔ１０２Ｃ多态性在氯氮平药理作用机制中起重要的作用。

5-HT2A受体基因多态性与奥氮平疗效的关联研究

目的 探讨广州地区汉族人群中5-HT2A受体A1438G和T102C基因多态性与奥氮平疗效的关系。方法 随机抽取143例精神分裂症患者,奥氮平单药治疗8周。治疗前后以阳性和阴性症状量表（PANSS）评定奥氮平临床疗效,按照PANSS减分率≥50%和〈50%分为有效组和无效组。采用聚合酶链反应-限制性片段长度多态性方法（PCR-RFLP）分析5-HT2A受体基因A1438G和T102C多态性。结果 （1）A1438G和T102C多态位点的基因型和等位基因在有效组和无效组之间分布均差异无显著性（P〉0.05）;（2）治疗前A1438G不同基因型患者的阳性症状分及阴性症状分有显著性差异,携GG片段基因的患者阳性症状分为（22.3±2.9）分,显著低于AA型及AG型患者[（25.1±4.2）分;（25.9±3.6）分],而阴性症状分为（23.4±9.2）分,较AA型及AG型明显高;（3）经8周治疗后,携带AA型患者PANSS总减分率、阳性症状减分率、阴性症状减分率、一般精神病理症状减分率均比AG型和GG型患者减分率高,但差异无显著性;（4）各临床指标、PANSS分值及其减分率在T102C不同基因亚型间均差异无显著性（P〉0.05）。结论 5-HT2A受体A1438G和T102C基因多态性与广东地区汉族人群奥氮平疗效不存在关联,但GG基因型可能与精神分裂症的阴性症状严重程度有正关联,而与阳性症状严重程度成负关联。

氯丙嗪对精神分裂症的疗效与5-HT2a受体基因的关系

目的 探讨与氯丙嗪对精神分裂症疗效有关的 5 HT2a受体基因的基因型以及其他相关的因素。方法 抽取 10 5例连续住院的精神分裂症患者 ,给予氯丙嗪≥ 30 0mg/d治疗 2个月 ,用PANSS量表评定氯丙嗪疗效 ,用多聚酶链式反应扩增及限制性片段长度多态性 (PCR RFLPs)技术测定所研究对象的基因型和等位基因。所得资料以 χ2 、t检验及Logistic回归分析。结果 发现氯丙嗪对精神分裂症患者的疗效与患者总病程明显负相关 ,而与 5 HT2a受体基因以及其他因素无关。结论 氯丙嗪对病程越短的精神分裂症患者疗效越好 ;5

儿童焦虑症与5-HT2A受体基因多态性的关联分析

目的 探讨儿童焦虑症与5-HT2A受体基因多态性之间的遗传关联。方法 采用聚合酶链式反应(PCR)和限制性片段长度多态性(RFLPs)方法,对61个符合DSM-Ⅳ与CCMD-2-R诊断标准的焦虑症儿童及其父母的5-HT2A受体基因多态性进行分型,分型结果用单体型相对风险方法(CHRR和HHRR)与传递不平衡检验(TDT)进行分析。结果 儿童焦虑症与5-HT2A受体基因无显著性关联。CHRR、HHRR和TDT值分别为2.3607～0.9213,1.0955和1.88,P值均>0.05。结论 儿童焦虑症与5-HT2A受体基因T102C多态性无关联。

中国首次发作的精神分裂症患者5-HT_(2A)受体基因多态性与阴性症状的关系(英文)

目的:研究5-HT2A受体T102C基因多态性是否与首次发作的中国精神分裂症患者症状严重程度以及阴性症状相关。方法:201名首次发作的中国精神分裂症患者入组。运用PCR-RFLP技术鉴定5-HT2A受体基因T102C基因型,PANSS量表评估药物治疗前精神症状严重程度。结果:5-HT2A受体102-T/T基因型与治疗前PANSS总基线分和阴性症状分量表分显著相关,但是与阳性症状和一般精神病理症状量表分无相关性。结论:5-HT2A受体T102C基因功能多态性可能在中国汉族精神分裂症阴性症状和预后中起一定作用。

脑力劳动者职业紧张与5-HT2A受体基因rs6313位点多态性对睡眠质量影响的研究

目的探讨脑力劳动者职业紧张与5-羟色胺(HT)2A受体基因rs6313位点多态性对睡眠质量的影响。方法 (1)采用分层整群随机抽样方法抽取年龄在18~60岁间的职业人员2 400名,运用职业紧张测量问卷(OSI-R)和匹兹堡睡眠质量指数量表(PSQI)分别对其职业紧张程度和睡眠质量情况进行问卷调查。(2)抽取825名职业人员,运用SNaPshot法检测5-HT2A受体基因rs6313位点的基因型。结果与国内常模相比,脑力劳动者的职业任务(ORQ)和个体紧张反应(PSQ)得分均高于国内常模,个体应对资源(PRQ)得分低于国内常模(P<0.05);职业紧张程度与睡眠质量间的差异有统计学意义(P<0.05);5-HT2A受体基因rs6313位点基因在有无睡眠质量问题两组间的分布无统计学差异(P>0.05)。结论脑力劳动者职业紧张程度与睡眠质量之间具有相关性;5-HT2A受体基因rs6313位点多态性可能与脑力劳动者的睡眠质量无关。

拟黑多刺蚁5-HT2A受体基因cDNA的克隆及表达

【目的】克隆拟黑多刺蚁(Polyrhachis vicina Roger)5-HT2A受体基因的cDNA序列,并对其核苷酸序列和系统进化进行分析,检测其在拟黑多刺蚁不同发育阶段幼虫和不同品级成虫mRNA的表达情况,为探究5-HT2A受体基因对拟黑多刺蚁生长发育的调控规律提供证据。【方法】从拟黑多刺蚁中提取总RNA,RT-PCR扩增并克隆Pv5-HT2A受体基因;用ProtParam预测蛋白质序列,Blast比较蛋白质序列同源性,用Clustal X进行核酸和氨基酸序列比对,MEGA 6.0比邻法生成系统进化树。利用荧光实时定量PCR检测Pv5-HT2A受体基因在拟黑多刺蚁不同发育阶段幼虫及不同品级成虫mRNA的表达水平。【结果】克隆得到Pv5-HT2A受体基因的cDNA序列,全长2 965bp,开放阅读框长1 926bp,编码641个氨基酸。疏水性分析显示,Pv5-HT2A受体氨基酸具有7个跨膜疏水区,属于典型的G蛋白偶联受体类型。系统发育分析表明,拟黑多刺蚁与红收获蚁的亲缘关系最近,相似度达69%。荧光实时定量PCR结果显示,拟黑多刺蚁5-HT2A mRNA在不同发育阶段和不同品级成虫中均有表达,其中卵、3龄幼虫及蛹期的表达量较高;成虫中,雄蚁表达量最高,雌蚁的表达量最低。【结论】拟黑多刺蚁与其他昆虫的5-HT2A受体基因存在相关性,推测5-HT2A受体基因对拟黑多刺蚁的生长发育具有一定调节作用。

Association between Low-density Lipoprotein Receptor-related Protein 5 Polymorphisms and Type 2 Diabetes Mellitus in Han Chinese:a Case-control Study

Objective To investigate the association between low-density lipoprotein receptor-related protein 5 （LRPS） variants （rs12363572 and rs4930588） and type 2 diabetes mellitus （T2DM） in Han Chinese. Methods A total of 1842 T2DM cases （507 newly diagnosed cases and 1335 previously diagnosed cases） and 7777 controls were included in this case-control study. PCR-RFLP was conducted to detect the genotype of the two single nucleotide polymorphisms （SNPs）. Odds ratios （ORs） and 95% confidence intervals （95% CIs） were calculated to describe the strength of the association by logistic regression. Results In the study subjects, neither rs12363572 nor rs4930588 was significantly associated with T2DM, even after adjusting for relevant covariates. When stratified by body mass index （BMI）, the two SNPs were also not associated with T2DM. Among the 3 common haplotypes, only haplotype ~ was associated with reduced risk of T2DM （OR 0.820, 95% CI 0.732-0.919）. In addition, rs12363572 was associated with BMI （P〈0.001） and rs4930588 was associated with triglyceride levels （P=0.043） in 507 newly diagnosed T2DM cases but not in healthy controls. Conclusion No LRP5 variant was found to be associated with T2DM in Han Chinese, but haplotype TT was found to be associated with T2DM.

Thalamic Nucleus Reuniens Glutamatergic Neurons Mediate Colorectal Visceral Pain in Mice via 5-HT2B Receptors

Irritable bowel syndrome(IBS)is a common functional bowel disorder characterized by abdominal pain and visceral hypersensitivity.Reducing visceral hypersensitivity is the key to effectively relieving abdominal pain in IBS.Increasing evidence has confirmed that the thalamic nucleus reuniens(Re)and 5-hydroxytryptamine(5-HT)neurotransmitter system play an important role in the development of colorectal visceral pain,whereas the exact mechanisms remain largely unclear.In this study,we found that high expression of the 5-HT2B receptors in the Re glutamatergic neurons promoted colorectal visceral pain.Specifically,we found that neonatal maternal deprivation(NMD)mice exhibited visceral hyperalgesia and enhanced spontaneous synaptic transmission in the Re brain region.Colorectal distension(CRD)stimulation induced a large amount of c-Fos expression in the Re brain region of NMD mice,predominantly in glutamatergic neurons.Furthermore,optogenetic manipulation of glutamatergic neuronal activity in the Re altered colorectal visceral pain responses in CON and NMD mice.In addition,we demonstrated that 5-HT2B receptor expression on the Re glutamatergic neurons was upregulated and ultimately promoted colorectal visceral pain in NMD mice.These findings suggest a critical role of the 5HT2B receptors on the Re glutamatergic neurons in the regulation of colorectal visceral pain.

Inhibition of 5-HT_3 Receptors-activated Currents by Cannabinoids in Rat Trigeminal Ganglion Neurons

This study investigated the modulatory effect of synthetic cannabinoids WIN55,212-2 on 5-HT3 receptor-activated currents (I5-HT3) in cultured rat trigeminal ganglion (TG) neurons using whole-cell patch clamp technique. The results showed that: (1) The majority of examined neurons (78.70%) were sensitive to 5-HT (3–300 μmol/L). 5-HT induced inward currents in a concentration-dependent manner and the currents were blocked by ICS 205-930 (1 μmol/L), a selective antagonist of the 5-HT3 receptor; (2) Pre-application of WIN55,212-2 (0.01–1 μmol/L) significantly inhibited I5-HT3 reversibly in concentration-dependent and voltage-independent manners. The concentra-tion-response curve of 5-HT3 receptor was shifted downward by WIN55,212-2 without any change of the threshold value. The EC50 values of two curves were very close (17.5±4.5) mmol/L vs. (15.2±4.5) mmol/L and WIN55,212-2 decreased the maximal amplitude of I5-HT3 by (48.65±4.15)%; (3) Neither AM281, a selective CB1 receptor antagonist, nor AM630, a selective CB2 receptor antagonist reversed the inhibition of I5-HT3 by WIN55,212-2; (4) When WIN55,212-2 was given from 15 to 120 s before 5-HT application, inhibitory effect was gradually increased and the maximal inhibition took place at 90 s, and the inhibition remained at the same level after 90 s. We are led to concluded that-WIN55,212-2 inhibited I5-HT3 significantly and neither CB1 receptor antagonist nor CB2 receptor antagonist could reverse the inhibition of I5-HT3 by WIN55,212-2. Moreover, WIN55,212-2 is not an open channel blocker (OCB) of 5-HT3 receptor. WIN55,212-2 significantly inhibited 5-HT-activated currents in a non-competitive manner. The inhibition of I5-HT3 by WIN55,212-2 is probably new one of peripheral analgesic mechanisms of WIN55,212-2, but the mechanism by which WIN55,212-2 inhibits I5-HT3 warrants further investigation.

Rivastigmine Restores 5-HT_1AReceptor Levels in the Hippocampus of Olfactory Bulbectomized Mice

Rivastigmine, a dual acetylcholinesterase and butyrylcholinesterase inhibitor, is used for symptomatic treatment of patients with mild to moderately severe dementia in Alzheimer’s disease (AD) patients. In the present study, we found that 5-HT1A receptor (5-HT1AR) is downregulated, whereas 5-HT2A receptor (5-HT2AR) is upregulated in the hippocampal dentate gyrus (DG) and CA1 region by olfactory bulbectomy (OBX) in mice. Furthermore, chronic treatment with rivastigmine (1.0 mg/kg) for 2 weeks starting 2 weeks after OBX operation restored the decreased 5-HT1AR and the increased 5-HT2AR levels. To determine whether cholinergic receptor stimulation by rivastigmine is involved in the rivastigmine-induced regulation of 5-HTR levels, we treated the mice with mecamylamine (2.5 mg/kg), or atropine (5.0 mg/kg) with rivastigmine (1.0 mg/kg) once a day for 2 weeks. Notably, the rivastigmine-induced 5-HT1AR upregulation was eliminated by mecamylamine but not by atropine treatments. On the other hand, the restored 5-HT2AR level by rivastigmine was not affected by either mecamylamine or atropine. Treatment with 8-OH-DPAT, a selective 5-HT1AR agonist improved the decreased 5-HT1AR and the increased 5-HT2AR levels in OBX mice. On the other hand, treatment with TCB-2, a potent 5-HT2AR agonist had no effects on the 5-HT1AR and 5-HT2AR dysregulation in OBX mice. Taken together, nicotinic acetylcholine receptor (nAChR) stimulation mediates rivastigmine-induced upregulation of 5-HT1AR. Therefore, we speculate that the increased ACh levels by rivastigmine can stimulate nAChR located on serotonergic nerve terminals and stimulate 5-HT1AR by the enhanced 5-HT release in the hippocampus. The 5-HT1AR stimulation likely mediates the improvement of 5-HT1AR levels as auto-receptor in OBX hippocampus.