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.

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 Activation and Blockade of Serotonin 5-HT1A Receptors on the Immune Response in Rats Selected for Different Levels of Aggressiveness

The present study examines the effects of serotonin (5-HT) 1A receptor ligands on humoral im-mune response in two rat lines selected for over 75 generations for the enhancement or elimination of aggression. Activation of presynaptic 5-HT1A receptors with a low dose of the selective 5-HT1A receptor agonist 8-OH-DPAT (0.1 mg/kg) or the blockade of postsynaptic 5-HT1A receptors with the antagonist WAY-100635 (1.0 mg/kg) did not affect the numbers of IgM-antibody forming cells (IgM-AFC) in the spleen of highly aggressive rats, which were characterized by higher immune responsiveness compared to nonaggressive line. On the other hand, the same doses of 8-OH-DPAT and WAY-100635, as well as a higher dose of 8-OH-DPAT (1.0 mg/kg), which is known to activate postsynaptic 5-HT1A receptors, produce immunostimulation in nonaggressive rats. However, only the highest dose of 8-OH-DPAT (5.0 mg/kg) was able to cause immunosuppression in nonaggressive rats that was mainly dependent on stimulation of postsynaptic 5-HT1A receptors. In contrast to nonaggressive rats, the dose of 1.0 mg/kg 8-OH-DPAT was sufficient to produce a decrease in the numbers of IgM-AFC in highly aggressive rats. Thus, pharmacological activation of pre- and postsynaptic 5-HT1A receptors, as well as the blockade of postsynaptic 5-HT1A receptors, produced different effects on the immune response in two lines of rats selected for high level of aggression or its absence. These data may have implications for more efficient treatments of a number of mental disorders associated with abnormal aggression.

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.

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.

5-HT_(2A)受体在延髓面神经后核内侧区偶联O_2^-的作用

目的探讨5-HT2A受体偶联O2-在延髓面神经后核内侧区(mNRF)对呼吸调控作用中的可能信号转导通路。方法制作新生大鼠体外延髓脑片标本,进一步参照Johnson方法制作mNRF“岛”,逐个移入mNRF“岛”于按预案加有试剂的带盖24孔板,24孔板置入5%CO2、37℃培养箱培养60min;取上清液100μl,用可见分光光度计(波长550nm)检测吸光度。分别观察5-HT、5-HT2A受体激动剂盐酸2,5-二甲氧基-4-碘苯基丙烷(DOI)对mNRF产生O2-的影响,及5-HT2A受体拮抗剂凯坦色林(Ketanserin)、抗氧化剂α-硫辛酸(α-LA)能否抑制5-HT及DOI在mNRF“岛”产生O2-的作用。结果5-HT的浓度曲线显示5-HT在1μmol/L时对mNRF作用达到峰值,随着浓度增加,O2-无显著增加;DOI浓度曲线显示DOI使mNRF产生的O2-达到峰值的浓度是20μmol/L;5-HT、DOI均可显著使mNRF产生的O2-增加(P<0.01),而5-HT、DOI之间无显著性差异,Ketanserin、α-LA可显著抑制5-HT、DOI在mNRF产生O2-。结论在mNRF通过激活5-HT2A受体,可显著产生O2-,提示5-HT2A受体对呼吸的调控可能与O2-相关。

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.

5-羟色胺2C受体基因启动子区-759C/T多态性与甘肃东乡族2型糖尿病的关系

目的:探讨5-羟色胺2C受体(HTR2C)基因启动子区-759C/T多态性与甘肃东乡族2型糖尿病(T2DM)和肥胖的相关性.方法:应用PCR-连接酶检测反应(PCR-LDR)方法检测100名T2DM患者(T2DM组)和126名健康对照者(NC组)HTR2C基因-759C/T多态性,并测量身高、体质量、腰围、臀围、血压、血脂、空腹血糖及空腹胰岛素.结果:①女性NC组和T2DM组CC,CT基因型频率分别为61%,39%,80.6%,19.4%,T2DM组CT基因型频率明显低于NC组(P=0.047);两组C,T等位基因频率分布差异无统计学意义(P=0.073);男性NC组和T2DM组C,T半合子型频率差异无统计学意义(P=0.727);②女性CC,CT基因型及C,T等位基因频率和男性C,T半合子型频率在非肥胖组和肥胖组差异无统计学意义.结论:HTR2C基因启动子区-759C/T多态性与甘肃东乡族女性T2DM相关联,-759C→T单核苷酸置换可能是防止女性发生T2DM的基因保护性因子.

Domesticated HERV-W env contributes to the activation of the small conductance Ca^(2+)-activated K^(+)type 2 channels via decreased 5-HT4 receptor in recent-onset schizophrenia

The human endogenous retroviruses type W family envelope(HERV-W env)gene is located on chromosome 7q21-22.Our previous studies show that HERV-W env is elevated in schizophrenia and HERV-W env can increase cal-cium influx.Additionally,the 5-HTergie system and particularly 5-hydroxytryptamine(5-HT)receptors play a prominent role in the pathogenesis and treatment of schizophrenia.5-hydroxytryptamine receptor 4(5-HT4R)agonist can block calcium channels.However,the underlying relationship between HERV-W env and 5-HT4R in the etiology of schizophrenia has not been revealed.Here,we used enzyme-linked immunosorbent assay to detect the concentration of HERV-W env and 5-HT4R in the plasma of patients with schizophrenia and we found that there were decreased levels of 5-HT4R and a negative correlation between 5-HT4R and HERV-W env in schizophrenia.Overexpression of HERV-W env decreased the transcription and protein levels of 5-HT4R but increased small conductance Ca^(2+)-activated K^(+)type 2 channels(SK2)expression levels.Further studies revealed that HERV-w env could interact with 5-HT4R.Additionally,luciferase assay showed that an essential region(-364 to-176 from the transcription start site)in the SK2 promoter was required for HERV-W env-induced SK2 expression.Importantly,5-HT4R participated in the regulation of SK2 expression and promoter activity.Electrophysiological recordings suggested that HERV-Wenv could increase SK2 channel currents and the increase of SK2 currents was inhibited by 5-HT4R.In condusion,HERV-W env could activate SK2 channels via decreased 5-HT4R,which might exhibit a novel mechanism for HERV-Wenv to influence neuronal activity in schizophrenia.

Molecular signaling of 5-HT_1Aand presence of serotonergic cells in the fetal cerebral cortex

Early appearance of the serotonergic system in the fetal brain and the various effects of serotonin (5-HT) on brain morphogenesis, have given support to a neurotrophic role of serotonin. This function of serotonin is accomplished through a system of serotonin nerve terminals in the target regions that involves various 5-HT receptors. In visual, auditory and somatosensory cortex an early and intense serotonergic innervation is particularly important. The neuronal somata of these terminals are normally located in the mesencephalon and they have not been observed in the maturing cerebral cortex, neither in the adult brain. By using immunolabeling techniques, fluorescence and confocal microscopy, we observe the presence of both, 5-HT terminals and 5-HT cells in mesencephalon (Me, E17) and in the neopallium (Np, E13-E16) cocultures. Cells immunopositive to 5-HT and to tryptophan-5-hydroxilase are also observed in the Np on day 12 of culture. These results concerning the unexpected presence of serotonergic cells in the fetal cerebral cortex are interesting and may be of importance in corticogenesis. As it happens with other elements of the serotonergic system, the presence of these phenotypically serotonergic cells in the early cerebral cortex may be transitory and probably supporting cortex maturation processes. The molecular signaling path of the 5-HT1A receptor has also been identified.

Changes of Serotonin （5-HT）, 5-HT2A Receptor, and 5-HT Transporter in the Sprague-Dawley Rats of Depression, Myocardial Infarction and Myocardial Infarction Co-exist with Depression

Background： To evaluate whether serotonin （5-HT）, 5-HT2A receptor （5-HT2AR）, and 5-HT transporter （serotonin transporter [SERT]） are associated with different disease states of depression, myocardial infarction （MI） and MI co-exist with depression in Sprague-Dawley rats. Methods： After established the animal model of four groups include control, depression, MI and MI with depression, we measured 5-HT, 5-HT2AR and SERT from serum and platelet lysate.Results： The serum concentration of 5-HT in depression rats decreased significantly compared with the control group （303.25 ± 9.99 vs. 352.98 ±13.73; P =0.000）, while that in MI group increased （381.78 ±14.17 vs. 352.98 ±13.73; P = 0.000）. However, the depression ＋ MI group had no change compared with control group （360.62 ±11.40 vs. 352.98 ±13.73; P = 0.036）. The changes of the platelet concentration of 5-HT in the depression, MI, and depression ＋ MI group were different from that of serum. The levels of 5-HT in above three groups were lower than that in the control group （380.40 ± 17.90, 387.75 ±22.28,246.40 ±18.99 vs. 500.29 ±20.91 ; P = 0.000）. The platelet lysate concentration of 5-HT2AR increased in depression group, MI group, and depression ＋ MI group compared with the control group （370.75 ±14.75,393.47 ±15.73,446.66 ±18.86 vs. 273.66 ±16.90; P= 0.000）. The serum and platelet concentration of SERT in the depression group, MI group and depression ＋ MI group were all increased compared with the control group （527.51 ±28.32, 602.02 ±23.32, 734.76 ±29.59 vs. 490.56 ±16.90; P 0,047, P = 0.000, P = 0.000 in each and 906.38 ±51.84, 897.33 ±60.34, 1030.17 ±58.73 vs. 708.62 ±51.15; P = 0.000 in each）. Conclusions： The concentration of 5-HT2AR in platelet lysate and SERT in serum and platelet may be involved in the pathway of MI with depression. Further studies should examine whether elevated 5-HT2AR and SERT may contribute to the biomarker in MI patients with depression.

Sleep Deprivation Selectively Down-Regulates Astrocytic 5-HT2B Receptors and Triggers Depressive-Like Behaviors via Stimulating P2X7 Receptors in Mice

Chronic loss of sleep damages health and disturbs the quality of life.Long-lasting sleep deprivation(SD)as well as sleep abnormalities are substantial risk factors for major depressive disorder,although the underlying mechanisms are not clear.Here,we showed that chronic SD in mice promotes a gradual elevation of extracellular ATP,which activates astroglial P2X7 receptors(P2X7Rs).Activated P2X7Rs,in turn,selectively down-regulated the expression of 5-HT2B receptors(5-HT2BRs)in astrocytes.Stimulation of P2X7Rs induced by SD selectively suppressed the phosphorylation of AKT and FoxO3 a in astrocytes,but not in neurons.The overexpression of FoxO3a in astrocytes inhibited the expression of 5-HT2BRs.Down-regulation of 5-HT2BsRs instigated by SD suppressed the activation of STAT3 and relieved the inhibition of Ca2+-dependent phospholipase A2.This latter cascade promoted the release of arachidonic acid and prostaglandin E2.The depression-like behaviors induced by SD were alleviated in P2X7R-KO mice.Our study reveals the mechanism underlying chronic SD-induced depression-like behaviors and suggests 5-HT2BRs as a key target for exploring therapeutic strategies aimed at the depression evoked by sleep disorders.

Serotonin regulates brain-derived neurotrophic factor expression in select brain regions during acute psychological stress

Previous studies suggest that serotonin （5-HT） might interact with brain-derived neurotrophic factor （BDNF） during the stress response. However, the relationship between 5-HT and BDNF expression under purely psychological stress is unclear. In this study, one hour before psychological stress exposure, the 5-HT1A receptor agonist 8-OH-DPAT or antagonist MDL73005, or the 5-HT2A receptor agonist DOI or antagonist ketanserin were administered to rats exposed to psychological stress. Immunohistochemistry and in situ hybridization revealed that after psychological stress, with the exception of the ventral tegmental area, BDNF protein and mRNA expression levels were higher in the 5-HT1A and the 5-HT2A receptor agonist groups compared with the solvent control no-stress or psychological stress group in the CA1 and CA3 of the hippocampus, prefrontal cortex, central amygdaloid nucleus, dorsomedial hypothalamic nucleus, dentate gyrus, shell of the nucleus accumbens and the midbrain periaqueductal gray. There was no significant difference between the two agonist groups. In contrast, after stress exposure, BDNF protein and mRNA expression levels were lower in the 5-HT1A and 5-HT2A receptor antagonist groups than in the solvent control non-stress group, with the exception of the ventral tegmental area. Our findings suggest that 5-HT regulates BDNF expression in a rat model of acute psychological stress.

Heat-Killed <i>Lactobacillus brevis</i>SBC8803 Induces Serotonin Release from Intestinal Cells

Previously, we reported that changes induced in autonomic neurotransmission in rats by Lactobacillus brevis SBC8803 may be mediated by serotonin 3 (5-HT3) receptors. In this study, we evaluated the effects of heat-killed L. brevis SBC8803 on serotonin (5-HT) releasing from intestinal cells. In the in vitro study, L. brevis SBC8803 stimulated 5-HT release from cultured rat endocrine RIN-14B cells (SBC8803 vs. sterile water;P in vivo study, 2 mg of heat-killed L. brevis SBC8803 was administered using a stomach sonde (feeding needle) to C57BL/6J mice. Analysis of plasma by ELISA showed gradually increase in 5-HT concentrations (0 min vs. 60 min;P ex vivo cultured intestinal loops composed of duodenum and part of the jejunum, from C3H/HeN and C57BL/6J male mice indicated that L. brevis SBC8803 effectively induced 5-HT release (SBC8803 vs. sterile water;P L. brevis SBC8803 may stimulate 5-HT release from mouse intestinal cells such as enterochromaffin cells.

Bioassay-guided isolation of saikosaponins with agonistic activity on 5-hydroxytryptamine 2C receptor from Bupleurum chinense and their potential use for the treatment of obesity

5-Hydroxytryptamine 2C(5-HT2C) receptor is one of the major targets of anti-obesity agents, due to its role in regulation of appetite. In the present study, the 70% EtO H extract of the roots of Bupleurum chinense was revealed to have agonistic activity on 5-HT2 C receptor, and the subsequent bioassay-guided isolation led to identification of several saikosaponins as the active constituents with 5-HT2 C receptor agonistic activity in vitro and anti-obesity activity in vivo. The new compound, 22-oxosaikosaponin d(1), was determined by extensive spectroscopic analyses(HR-ESI-MS, IR, and 1D and 2D NMR). The primary structure-activity relationship study suggested that the intramolecular ether bond between C-13 and C-28 and the number of sugars at C-3 position were closely related to the 5-HT2 C receptor agonistic activity. Saikosaponin a(3), the main saponin in B. chinense, showed obviously agonistic activity on 5-HT2 C receptor with an EC50 value of 21.08 ± 0.33 μmol×L^(–1) in vitro and could reduce food intake by 39.1% and 69.2%, and weight gain by 13.6% and 16.4%, respectively, at 3.0 and 6.0 mg×kg^(–1) in vivo. This investigation provided valuable information for the potential use of B. chinense as anti-obesity agent.

Effects of Kaixin Powder on Expression of 5-HT Receptor in Hippocampus of Depressed Rats Induced by CUMS

Objective To observe the influence of Kaixin Powder on ethology,content of 5-HT in the hippocampus, expression of m RNA, and protein in 5-HT1 A and 5-HT2 A receptors in the hippocampus of depressed rats induced by chronic unpredictable mild stress（CUMS）. Methods Twenty-four male Wistar rats were randomly divided into blank,model, Trazodone, and Kaixin Powder groups, six rats in each group. In addition to the blank control group, other groups were established the depression model induced by CUMS combined with isolated feeding. At the same time, Trazodone group and Kaixin Powder group were treated with corresponding drugs for 3 weeks. After 3 weeks of administration, the rats were sacrificed, and a series of indexes were measured such as the contents of 5-HT, m RNA expression levels of 5-HT1 A and 5-HT2 A receptors, protein expression levels of 5-HT1 A and 5-HT2 A receptors, and so on. Results A series of indexes in the model group were decreased significantly such as the body weight growth, the sugar water intake, the score of Open Field Test, the content of5-HT in the hippocampus, expression of m RNA, and protein in 5-HT1 A receptor, while the expression of m RNA and protein in 5-HT2 A receptor were increased significantly.Compared with the model group, the indexes were ameliorated in Trazodone and Kaixin Powder groups. Kaixin Powder is better than Trazodone in decreasing the level of protein in 5-HT2 A receptor. Conclusion The result indicated that the depression performance of depressed rats induced by CUMS can be ameliorated by Kaixin Powder,and the mechanism maybe concerned with increasing the contents of 5-HT, exciting 5-HT1 A receptor, and antagonising 5- HT2 A receptor.

Synthesis and biological evaluation of ^(99m)Tc-HEDTA/HYNIC-MPP4 complex for 5-HT1A receptor imaging

5-HT1A receptor is associated with a variety of pathophysiology of neuropsychiatric disorders. Accordingly, we have synthesized a new 5-HT1A receptor ligand (HYNIC-MPP4) and labeled it with 99mTc using N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) as coligand. 99mTc-HEDTA/HYNIC-MPP4 was prepared under pH 6 at room temperature. Biodistribution of 99mTc-HEDTA/HYNIC-MPP4 in normal mice showed that this complex had moderate brain uptake (0.60% ID·g-1 at 2 min p.i.) and good retention. The hippocampus had the highest radioactivity uptake at 2 min p.i. (1.84% ID·g-1). The ratio of Hipp/CB was 3.1 at 2 min p.i. and increased to 4.4 at 60 min p.i. After blocking with 8-hydroxy-2-(dipropylamino) tetralin, the uptake of hippocampus was decreased significantly from 1.84% ID·g-1 to 0.53% ID·g-1 at 2 min p.i., while the cerebellum had no significant decrease. This 99mTc complex could be a potent agent for 5-HT1A receptor imaging.

Altered serotonin metabolism in Takeda G protein-coupled receptor 5 knockout mice protects against diet-induced hepatic fibrosis

Background and aims:Diet-induced obesity and metabolic syndrome can trigger the progression of fatty liver disease to non-alcoholic steatohepatitis and fibrosis,which is a major public health concern.Bile acids regulate metabolic homeostasis and inflammation in the liver and gut via the activation of nuclear farnesoid X receptor(Fxr)and the membrane receptor Takeda G protein-coupled receptor 5(Tgr5).Tgr5 is highly expressed in the gut and skeletal muscle,and in cholangiocytes and Kupffer cells of the liver.Tgr5 is implicated in the mediation of liver and gut inflammation,as well as the maintenance of energy homeostasis.Here,we used a high fat,high fructose,and high sucrose(HFS)diet to determine how bile acid signaling through Tgr5 may regulate metabolism during the progression from fatty liver to non-alcoholic steatohepatitis and fibrosis.Materials and methods:Female C57BL/6J control wild type(WT)and Tgr5 knockout(Tgr5^(-/-))mice were fed HFS(high fat(40%kcal),high fructose,and 20%sucrose water)diet for 20 weeks.Metabolic phe-notypes were characterized through examination of bile acid synthesis pathways,lipid and cholesterol metabolism pathways,and fibrosis and inflammation pathways.Results:Tgr5^(-/-)mice were more glucose intolerant when fed HFS diet,despite gaining the same amount of weight as WT mice.Tgr5^(-/-)mice accumulated significantly more hepatic cholesterol and triglycerides on HFS diet compared to WT mice,and gene expression of lipogenic genes was significantly upregulated.Hepatic cholesterol 7alpha-hydroxylase(Cyp7a1)gene expression was consistently elevated in Tgr5^(-/-)mice,while oxysterol 7alpha-hydroxylase(Cyp7b1),sterol 27-hydroxylase(Cyp27a1),Fxr,and small heterodimer partner(Shp)were downregulated by HFS diet.Surprisingly,hepatic inflammation and fibrosis were also significantly reduced in Tgr5^(-/-)mice fed HFS diet,which may be due to altered se-rotonin signaling in the liver.Conclusions:Tgr5^(-/-)mice may be protected from high fat,high sugar-induced hepatic inflammation and injury due to altered serotonin metabolism.

HTR2A agonists play a therapeutic role by restricting ILC2 activation in papain-induced lung inflammation

Group 2 innate lymphoid cells(ILC2s)are a category of heterogeneous cells that produce the cytokines IL-5 and IL-13,which mediate the type 2 immune response.However,specific drug targets on lung ILC2s have rarely been reported.Previous studies have shown that type 2 cytokines,such as IL-5 and IL-13,are related to depression.Here,we demonstrated the negative correlation between the depression-associated monoamine neurotransmitter serotonin and secretion of the cytokines IL-5 and IL-13 by ILC2s in individuals with depression.Interestingly,serotonin ameliorates papain-induced lung inflammation by suppressing ILC2 activation.Our data showed that the serotonin receptor HTR2A was highly expressed on ILC2s from mouse lungs and human PBMCs.Furthermore,an HTR2A selective agonist(DOI)impaired ILC2 activation and alleviated the type 2 immune response in vivo and in vitro.Mice with ILC2-specific depletion of HTR2A(Il5^(cre/+)·Htr2a^(flox/flox)mice)abolished the DOI-mediated inhibition of ILC2s in a papain-induced mouse model of inflammation.In conclusion,serotonin and DOI could restrict the type 2 lung immune response,indicating a potential treatment strategy for type 2 lung inflammation by targeting HTR2A on ST2+ILC2s.

Accommodation and peristalsis are functional responses to obstruction in rat hypertrophic ileum

AIM:To investigate the effects of chronic obstruction on enteric reflexes evoked by electrical stimulation (EFS) or intraluminal distension of the rat hypertrophic ileum.METHODS:Motor responses to EFS and to intraluminal distension were studied in the absence and in the presence of various inhibitors of enteric mediators.Ileum segments from operated (chronic ileal obstruction),sham-operated (control) and normal rats were horizontally mounted,connected to a pressure transducer and intraluminally perfused.The effects of selective serotonin receptor (5-HTR) blockers were investigated on distension-induced responses.The cellular localization of 5-HT3Rs was also examined in control and hypertrophic tissues through confocal microscopy.RESULTS:In non-obstructed segments,EFS elicited tetrodotoxin (TTX)-sensitive responses with high am-plitude contraction followed by weak relaxation.In hypertrophic tissues,EFS lowered the baseline pressure and evoked TTX-sensitive contractions significantly larger than normal (P < 0.01) or control (P < 0.05),and devoid of any relaxation phase (P < 0.01 vs normal).Incubation with atropine and guanethidine [nonadrenergic non-cholinergic (NANC) conditions] did not modify intestinal tone in normal and control preparations,but reversed the accommodation produced by EFS in hypertrophic tissues,and depressed the amplitude of contractions in all types of tissues.L-NAME and α-chymotrypsin blocked residual NANC motility in all tissues and augmented intraluminal pressure in hypertrophic segments (P < 0.05 vs NANC conditions).Intraluminal distension of the intestinal wall evoked non-propulsive cycles of contractions and relaxations in non-obstructed tissues.In all hypertrophic segments,strong propulsive strokes,markedly wider (P < 0.001),and larger than normal (P < 0.001) or control (P < 0.05) were elicited.Both motor patterns were blocked under NANC conditions and with simultaneous incubation with L-NAME and α-chymotrypsin.In all types of tissues,incubation with ketanserin or GR125487 did not modify distension-induced motility.In contrast,blockade of 5-HT3Rs by ondansetron concentration-dependently inhibited motor responses in normal and control tissues,but only slightly impaired enteric reflexes in the hypertrophic preparations.Finally,confocal microscopy did not reveal a different cellular distribution of 5-HT3Rs in control and hypertrophic ileum.CONCLUSION:Accommodation and distension-induced peristalsis of rat hypertrophic ileum are controlled by cholinergic and peptidergic transmission and are negligibly affected by 5-HT3Rs,which modulate distensioninduced motility in non-obstructed tissues.