下丘脑-垂体-肾上腺轴紊乱对焦虑性抑郁模型大鼠海马结构的影响

目的研究下丘脑-垂体-肾上腺(HPA)轴紊乱对焦虑性抑郁模型大鼠海马结构的影响,探讨焦虑性抑郁的潜在发病机制。方法将大鼠随机分为空白组、溶媒组、焦虑组、抑郁组和焦虑性抑郁组,每组12只。采用慢性束缚应激联合皮质酮注射方法建立焦虑性抑郁大鼠模型,连续21 d;造模后采用高架十字迷宫(EPM)、旷场实验(OFT)、强迫游泳实验(FST)评价大鼠焦虑和抑郁样行为;HE染色检测大鼠HPA轴各组织及海马病理变化;ELISA检测大鼠血浆中促肾上腺皮质激素释放激素(CRH)、促肾上腺皮质激素(ACTH)、皮质酮(CORT)含量;Western blot检测大鼠海马糖皮质激素受体(GR)蛋白表达。结果焦虑性抑郁组大鼠进入开臂的时间、次数及自主活动次数均与焦虑组相当,不动时间显著增加,与对照组及抑郁组比较有显著差异(P0.01或P0.05);HPA轴各组织均出现不同程度损伤,海马神经元肿胀,呈空泡状;同时,血浆中CRH、ACTH和CORT含量显著增加(P0.01或P0.05),海马GR表达显著下降。结论焦虑性抑郁模型组大鼠具有显著的焦虑及抑郁样行为,其发病机制可能与机体HPA轴紊乱及其引发的脑内海马损伤密切相关。     

连续单一应激后大鼠海马5-HT_(1A)受体活性与糖皮质激素受体表达的关系

目的:观察连续单一应激(SPS)大鼠海马糖皮质激素受体(GR)变化与5-HT1A受体的关系,探讨创伤后应激障碍的发病机制。方法:选用雄性成年Wistar大鼠45只,将大鼠随机分为对照组、模型组和阻断组,每组15只。模型组和阻断组给予SPS应激,其中阻断组大鼠在接受SPS前用55-HT1A受体阻断剂WAY100635预处理。采用免疫组织化学和免疫印迹技术测定海马GR水平,采用逆转录-聚合酶链式反应检测GRmRNA表达变化。结果:(1)免疫组织化学结果显示,模型组大鼠海马GR表达高于对照组(P0.01),阻断组则低于模型组(P0.05);(2)WesternBlot结果显示,模型组大鼠海马GR相对表达高于对照组(P0.01),阻断组低于模型组(P0.01);(3)RT-PCR结果表明,与对照组比较,模型组大鼠海马GRmRNA表达增强(P0.01);与模型组比较,阻断组表达量降低(P0.05)。结论:SPS海马GR表达变化与5-HT1A受体有关。     

促肾上腺皮质激素对慢性痛大鼠痛行为和海马内BDNF、CRF水平的影响

目的与方法:采用痛行为评分方法、免疫组化和原位杂交技术,观察促肾上腺皮质激素(ACTH)对完全福氏佐剂所致的关节炎大鼠海马内脑源性神经营养因子(BDNF)及其功能性受体trkB和促肾上腺皮质激素释放激素(CRH)水平的影响。结果:关节炎大鼠的痛行为评分显著高于正常对照组,同时注射侧对侧海马内BDNF免疫活性(IR)神经元、CRHmRNA阳性神经元和BDNF/CRHmRNA双染神经元数在注射佐剂后 2 4h显著高于正常对照组,而腹腔注射ACTH(2 5IU/kg或 12 5IU/kg)后,上述指标显著低于关节炎组;摘除双侧肾上腺后,腹腔注射ACTH的关节炎大鼠对侧海马内BDNF-IR、CRHmRNA阳性神经元和BDNF/CRHmRNA双染神经元数明显高于未摘除肾上腺的关节炎组。结论:海马内的BDNF和CRH参与慢性痛的调制,ACTH能抑制海马内BDNF和CRH的升高而产生镇痛作用,肾上腺对ACTH发挥其功能起决定性作用.     

慢性应激抑郁模型大鼠脑内5-HT1A和5-HT2A受体的变化

为了在5-羟色胺受体水平研究抑郁症的机制和三环类抗抑郁药物(TCAs)阿米替林的药理学机理,将24只SD雄性大鼠随机均分为三组,即对照组、抑郁组、阿米替林治疗组.应用[3H]8-OH-DPAT、[3H]Ketanserin作为标记配基,采用放射性配体受体结合法,分别测定大鼠海马5-HT1A受体、大脑皮层5-HT2A受体结合.结果显示抑郁大鼠海马 [3H]8-OH-DPAT 特异性结合(18.78±5.62 fmol/mg prot),较正常对照组(26.12±5.52fmol/mg prot )明显下降(P＜0.05).抑郁大鼠大脑皮层[3H]Ketanserin特异性结合(112.58±4.21fmol/mg prot),较正常对照组(86.28±4.24fmol/mg prot)明显增加( P＜0.05).阿米替林治疗3周后,可使抑郁大鼠海马5-HT1A受体与大脑皮层5-HT2A受体结合恢复正常.提示 海马5-HT1A受体结合下降、大脑皮层5-HT2A受体结合增加可能与抑郁症病因有关;海马5-HT1A受体、大脑皮层5-HT2A受体是阿米替林发挥抗抑郁作用的环节.     

应激大鼠下丘脑5-羟色胺1A受体活性与促肾上腺皮质激素释放因子表达的关系

目的:观察连续单一应激(SPS)前阻断大鼠5-羟色胺1A(5-HT1A)受体下丘脑促肾上腺皮质激素释放因子(CRF)表达的改变,初步探讨5-HT1A受体活性与CRF表达的关系.方法:将健康雄性Wistar大鼠分为对照组、模型组和阻断组,模型组和阻断组给予SPS.阻断组在给予SPS应激前使用5-HT1A受体阻断剂WAY100635进行干预.采用免疫组织化学和逆转录聚合酶链式反应(RT-PCR)方法检测下丘脑CRF蛋白和mRNA的表达.结果:对照组、模型组和阻断组免疫阳性细胞吸光度分别为6.94±0.61、22.36±1.55和16.86±1.65,mRNA相对表达分别为0.72±0.07、2.08±0.06和1.16±0.11,模型组高于对照组,阻断组低于模型组.结论:5-HT1A受体活性与下丘脑CRF表达有关.     

N-棕榈酰乙醇胺对慢性束缚应激小鼠焦虑抑郁样行为的影响

目的:采用慢性束缚应激小鼠模型,研究N-棕榈酰乙醇胺(N-palmitoylethanolamide,PEA)对小鼠焦虑抑郁样行为的影响,进一步探讨PEA抗小鼠焦虑抑郁作用的可能机制。方法:小鼠分为正常对照组、模型组、氟西汀(10 mg/kg)组和PEA 2.5、5、10 mg/kg组,每天灌胃给药后30 min,将小鼠(除了正常对照组)放置于有机玻璃管内接受4 h的慢性束缚应激,持续21 d。第22天采用旷场实验和强迫应激实验观察PEA对慢性束缚应激小鼠抑郁样行为的影响;高架十字迷宫实验探讨PEA对慢性束缚应激小鼠焦虑样行为的影响;水迷宫方法分析PEA对慢性束缚应激小鼠学习、记忆、空间定向和认知功能等方面的作用;ELISA方法检测慢性束缚应激小鼠血清促肾上腺皮质激素(adrenocorticotropic hormone,ACTH)、皮质醇(cortisol,CORT)及海马5-羟色胺(5-hydroxytryptamine,5-HT)含量的变化;可见分光光度法检测海马乙酰胆碱酯酶(acetylcholinesterase,ACh E)活性的改变。结果:与模型组相比,在小鼠强迫应激实验中,PEA及氟西汀组小鼠不动时间明显减少;旷场试验中,PEA及氟西汀明显增加小鼠水平移动距离及运动总时间,但只有PEA 10 mg/kg及氟西汀组增加了小鼠直立次数;在高架十字迷宫实验中,PEA及氟西汀明显增加小鼠开臂进入次数、开臂停留时间百分比及在臂总移动距离;在水迷宫实验中,PEA 5、10mg/kg及氟西汀组明显缩短小鼠寻台潜伏期,PEA 10 mg/kg及氟西汀组明显缩短小鼠搜寻距离。与应激模型组比较,PEA 2.5~10 mg/kg及氟西汀显著降低小鼠血清中ACTH水平,PEA 5、10 mg/kg及氟西汀显著降低小鼠血清CORT水平及小鼠肾上腺指数,PEA 10 mg/kg及氟西汀显著增高海马5-HT含量,降低海马ACh E活性,但PEA 2.5和5 mg/kg组海马组织中5-HT含量及ACh E活性则无明显改变。结论:PEA对束缚应激模型小鼠的焦虑及抑郁样行为具有一定的拮抗作用,其具体作用机制可能与调节下丘脑-垂体-肾上腺轴功能、增加海马单胺类递质5-HT水平及参与中枢胆碱系统的调节有关。     

褪黑素对创伤后应激障碍大鼠下丘脑-垂体-肾上腺轴的影响

目的:探讨褪黑素(MLT)对足部电击所致创伤后应激障碍(PTSD)大鼠下丘脑-垂体-肾上腺(HPA)轴的影响。方法:利用足底电击法制备大鼠PTSD模型,通过腹腔注射方法给予治疗组大鼠MLT。通过拒俘反应测试检测大鼠的行为学变化,利用real time RT-PCR方法检测下丘脑中促肾上腺皮质激素释放激素(CRH)mRNA的表达,利用酶联免疫吸附试验(ELISA)检测血清中促肾上腺皮质激素(ACTH)、肾上腺素(EPI)和糖皮质激素(GC)的含量。结果:PTSD组大鼠拒俘反应明显(P<0.05),下丘脑中CRH mRNA表达升高(P<0.05),血清中ACTH和EPI明显升高(P<0.05),但是GC水平下降(P<0.05)。MLT治疗后可以明显缓解PTSD大鼠拒俘反应(P<0.05),同时降低下丘脑中CRH mRNA表达(P<0.05),降低血清中ACTH和EPI水平并升高GC的水平(P<0.05)。结论:MLT治疗可缓解PTSD大鼠的症状,并恢复HPA轴的神经内分泌平衡。     

西酞普兰对戊四氮点燃癫痫大鼠行为学及海马5-HT能递质系统影响的在体微透析研究

为研究5-羟色胺(5-HT)能神经递质在癫痫形成过程中的变化及西酞普兰(CTP)对其的影响,本研究用CTP(1mg/kg.d灌胃)预干预1周后,对戊四氮(PTZ,30mg/kg.d,腹腔注射)点燃癫痫过程中的行为学及在不同时间点对大鼠海马进行微透析取样,经高效液相电化学检测技术在活体观察了30只自由活动大鼠5-HT及其代谢产物5-羟吲哚乙酸(5-HIAA)水平和5-HT转化率(5-HIAA/5-HT)的动态变化。结果显示:PTZ注射后在CTP组发作潜伏期延长,发作程度轻和点燃时间延长,发作死亡率降低。点燃早期,CTP组大鼠的海马5-HT水平升高,5-HT转化率降低,与对照组和PTZ组比较,有显著性差异(P<0.05);点燃晚期CTP组和PTZ组与对照组比较5-HT水平和5-HT转化率均显著降低(P<0.05)。本研究结果提示PTZ点燃过程中,早期CTP升高脑内5-HT水平,可能直接抑制了引起爆发放电的动作电位,而抑制发作;晚期脑内5-HT神经元丢失和受体减少,功能减退,而导致CTP的作用减退。     

不同应激方式中小鼠下丘脑与垂体中促肾上腺皮质激素释放激素、促肾上腺皮质激素表达与血清糖皮质激素水平的变化规律及加味逍遥丸的调节作用

目的了解心理和生理（小站台水环境复合）应激及纯心理（情绪）应激后不同时间小鼠下丘脑与垂体促肾上腺皮质激素释放激素（CRH）、促。肾上腺皮质激素（ACTH）的表达和血清糖皮质激素（GC）变化规律及加味逍遥丸的调节作用。方法利用小站台水环境装置应激动物和多功能条件反应箱电刺激小鼠激怒,而致试验鼠情绪紧张的纯心理应激方法制造动物模型;中药加味逍遥丸按2mg／g体重灌胃给药;免疫组化法检测CRH、ACTH蛋白;放射免疫法检测血清糖皮质激素含量。结果小站台水环境应激状态下,下丘脑CRH和垂体ACTH的表达面积都于3h明显增多;血清糖皮质激素于12h升高,并随应激时间延长继续升高。加味逍遥丸在小站台水环境应激72h时能减少下丘脑CRH、垂体ACTH的表达面积和降低反应强度,并下调血清糖皮质激素水平。在情绪应激状态下,下丘脑CRH和垂体ACTH表达面积和强度都于1d增多和增强,延长应激时间,下丘脑CRH、垂体ACTH表达和GC含量均维持在1d水平;加味逍遥丸在情绪应激5d时能降低下丘脑CRH表达强度,减少垂体ACTH的表达面积和降低强度,并下调血清糖皮质激素水平。结论小站台水环境应激状态下下丘脑CRH和垂体ACTH表达面积增多和反应强度明显增强;加味逍遥丸对应激造成的下丘脑CRH和垂体ACTH高表达有调节作用。情绪应激状态下下丘脑CRH和垂体ACTH表达面积增多和反应强度明显增强,加味逍遥丸对应激造成的下丘脑CRH和垂体ACTH高表达有调节作用。     

体力运动和心理应激对大鼠海马去甲肾上腺素和五-羟色胺水平的影响

目的：研究长期体力运动和慢性心理应激对大鼠中枢海马去甲肾上腺素(norepinephrine，NE)和五-羟色胺(serotonin，5-HT)水平的影响，并进一步探讨这2种神经递质在运动减缓应激性海马损伤效应中的作用。方法：采用了4周自愿跑轮运动(运动组)、3周束缚应激（应激组）和预先进行4周运动再施3周应激（运动-应激组）的实验动物模型，高效液相电化学法检测实验大鼠海马的NE和5-HT水平。结果：长期运动大鼠海马的NE和5-HT水平明显升高(P<0.01)，慢性应激大鼠的5-HT水平明显降低（P<0.05）；并且，先运动再应激组的海马NE水平维持正常并显著高于单纯应激组（P<0.01），而以上2组的5-HT水平并无显著差异，且均低于单纯运动组（P<0.05）。结论：在运动益于海马的正性作用中，NE和5-HT可能是重要的调控因素；在应激损伤海马的负性作用中，5-HT可能是重要的调控因素；而在运动减缓应激性海马损伤的作用途径中，NE可能是更重要的调控因素；并且，海马NE可能对运动更敏感，而5-HT可能对应激更敏感。     

The functional significance of biochemical alterations in streptozotocin-induced diabetes.

These experiments examined the effects of restraint stress on dopamine (DA) and 5-hydroxytryptamine (5-HT) and their principal metabolites dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA), respectively, in 4 brain regions, as well as on plasma corticosterone concentration (CORT) and behavior in streptozotocin-induced diabetic rats and nondiabetic controls. Diabetic rats had widespread reductions in DA and 5-HT turnover (DOPAC/DA and 5-HIAA/5-HT ratios). Restraint led to equivalent increases in DA turnover in diabetics and nondiabetics, but attenuated increases in 5-HT turnover in diabetic rats. CORT concentration of diabetics and nondiabetics measured in complete quiet did not differ. Relative to these measures, only diabetics had elevated CORT when either restrained or kept in the same room with restrained rats with food and water removed. Open-field exploration was suppressed by restraint in diabetics only. All diabetic rats showed decreased locomotion in a novel environment which was normalized during a second exposure to the apparatus. Together, these results suggest that diabetes-induced disruptions in open-field activity are related to anxiety rather than to motor or energy deficits, and may be related to impaired 5-HT and CORT systems.     

Serotonin and 5-hydroxyindoleacetic acid levels in discrete hypothalamic areas of the rat brain: relation to circulating corticosterone

We examined the influence of adrenalectomy (ADX), and chronic corticosterone (CORT) replacement, on serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) levels in discrete hypothalamic areas of the rat brain. A significant decrease in 5-HT (-25%) and 5-HIAA (-28%) content was observed in the paraventricular nucleus (PVN) 7 days following ADX. A similar decrease in 5-HT levels (-27%) was observed in the preoptic area (POM) following ADX. In contrast, 5-HT and 5-HIAA levels in the supraoptic nucleus (SON) were significantly elevated by 82% and 54%, respectively. Replacement therapy with subcutaneous CORT implants (200 mg) was effective in preventing these effects of ADX in some cases. These findings suggest that the pituitary-adrenal endocrine system may influence various physiological and behavioral functions via its action on serotonergic neurons within specific hypothalamic sites.     

Tryptophan, 5-HTP, 5-HT and 5-HIAA in the cerebrospinal fluid and sexual behavior in male rats

No changes were found in the concentration of tryptophan (Trp), 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT) or 5-hydroxyindole acetic acid (5-HIAA) in the cerebrospinal fluid (CSF) of male rats either before sexual activity, immediately after ejaculation of after the postejaculatory refractory period (PEI). Injection of the Trp hydroxylase inhibitor p-chlorophenylalanine (PCPA, 25 or 100 mg/kg i.p. for 3 days) in combination with an injection of the monoamine oxidase inhibitor pargyline (100 mg/kg i.p.) increased the concentration of Trp while decreasing the concentration of 5-HTP, 5-HT and 5-HIAA in the CSF. Furthermore 100 (but not 25) mg/kg PCPA in combination with pargyline caused a significant reduction in the latency to ejaculation. Injection of probenecid (200 mg/kg i.p.), an inhibitor of the transport of 5-HIAA from the CSF, increased the concentration of 5-HIAA in the CSF and slightly prolonged the latency to ejaculation. Sexual activity caused no further increase in CSF 5-HIAA levels in the probenecid-treated rats. Since drug-induced changes in sexual behavior are associated with marked alterations in 5-HT metabolism in the CSF, whereas the changes in the behavior which occur normally are not, these results question the physiological significance of the proposed inhibitory role of 5-HT in male rat sexual behavior.     

Sertraline behavioral response associates closer and dose-dependently with cortical rather than hippocampal serotonergic activity in the rat forced swim stress

The rat Forced Swim Test (FST) is widely used to investigate the response to antidepressant treatment. Selective serotonin reuptake inhibitors (SSRIs) elongate swimming duration during the FST, while climbing duration is unaffected. In the present study, we aimed to correlate behavioral effects of the SSRI sertraline in the FST with respective changes in the serotonergic activity of the hippocampus and the prefrontal cortex. Male rats were subjected to the standard FST (two swim sessions in two consecutive days) and between the two sessions they received three i.p. injections of sertraline (10mg/kg or 40mg/kg) or vehicle. All rats were killed immediately after the second FST session. Unstressed animals received the same administration schemes and were killed in equivalent time-points. Serotonin and its metabolite 5-HIAA were assayed in the hippocampus and the prefrontal cortex with the use of high-performance liquid chromatography (HPLC-ED) and their ratio 5-HIAA/5-HT was calculated. Sertraline enhanced swimming and decreased immobility duration at both doses. Serotonergic activity was not altered by the 2-day swim stress in either brain region, while subchronic sertraline treatment enhanced 5-HT levels and decreased 5-HIAA/5-HT in the hippocampus and the prefrontal cortex. The serotonin turnover rate (5-HIAA/5-HT ratio) decrease is probably indicative of reduced 5-HT metabolism, as a result of 5-HT reuptake inhibition. This effect was significant in the prefrontal cortex of unstressed rats only after a higher dose of sertraline. In the prefrontal cortex, but not in the hippocampus, immobility duration was negatively correlated with 5-HT tissue levels, whereas swimming duration was positively correlated with 5-HT. These results indicate that after antidepressant treatment, behavior during the FST can be predictive of respective serotonergic changes, especially in the prefrontal cortex.     

Studies on the neuroendocrine role of serotonin

The aim of the thesis was to investigate in male Wistar rats, the involvement of serotonin (5-HT) and 5-HT receptors in the regulation of the gene expression of hypothalamic hormones and in the secretion of the pituitary gland hormones prolactin (PRL), adrenocorticotropic hormone (ACTH), vasopressin (AVP) and oxytocin in basal and stress conditions. Furthermore, to study the significance of some distinctive central nuclei in these processes, and the metabolism of 5-HT in the hypothalamus and the dorsal raphe nucleus (DRN). The experiments were focused on (1) determination of involved neurons and nuclei (2) the hypothalamic level and (3) the pituitary gland level of regulation. The studies were typically performed in vivo but some studies were performed in vitro. Stereotactically neurotoxic lesion with 5,7-dihydroxy-5-HT in the dorsal raphe nucleus (DRN) or the hypothalamic paraventricular nucleus (PVN) reduced the ACTH and AVP response to stress, indicating an importance of these structures for this response. In situ hybridization on rat brain slices with oligopeptides showed an increase of corticotropin releasing hormone (CRH) mRNA in the PVN and proopiomelanocortin in the anterior pituitary lobe upon stimulation of the 5-HT1A, 5-HT1B, 5-HT2A and 5-HT2C receptors. Stimulation of 5-HT2A+2C receptors increased AVP mRNA in the PVN but not in the supraoptic nucleus (SON), whereas the level of oxytocin (OT) mRNA was increased both in the SON and the PVN and this effect was in addition mediated via 5-HT1A+1B receptors. Serotonin infused directly into the PVN by microdialysis stimulated local release of AVP. CRH was found to have a major role but not a complete responsibility in the 5-HT-induced release of ACTH, since immunoneutralisation of CRH inhibited the POMC gene expression and the ACTH response and since 5-HT and 5-HT antagonists were able to modulate the ACTH release from anterior pituitary gland cells in vitro. Through the years of investigation, the classification of the 7 main groups of 5-HT receptors (5-HT1 - 5-HT7) has changed due to molecular biological characterisation of the receptors and new receptors have been identified. With a battery of 5-HT agonists and antagonists several pharmacological experiments were performed with systemically or central administration of compounds and radioimmuno assay of plasma for pituitary gland hormone levels. Specific substances were not available for all 5-HT receptors and subreceptors thus some conclusions are a based on combination of experiments. The 5-HT induced PRL response is mediated via 5-HT1A, 5-HT2A, 5-HT2C and 5-HT3 receptors. In addition an involvement of 5-HT1B, 5-HT5 or 5-HT7 receptors seem possible. The ACTH response to 5-HT is mediated via 5-HT1A, 5-HT1B, 5-HT2A and 5-HT2C receptors and an involvement of the 5-HT4, 5-HT5 and 5-HT7 receptors is proposed. Peripheral secretion of AVP upon stimulation with 5-HT is mediated via 5-HT2C, 5-HT4 and 5-HT7 receptors but not 5-HT1A receptors. The secretion of OT is primarily mediated via 5-HT1A, 5-HT2C and 5-HT4 receptors and probably also 5-HT1B, 5-HT2A, 5-HT5A and 5-HT7 receptors. Physical and psychological stress activates hippocampal and hypothalamic 5-HT neurons. In contrast to other stress factors, restraint stress increases the content of 5-HT in the DRN but do not increase the metabolism of 5-HT and does not induce changes in hypothalamic levels of 5-HT. Large variations are found in the literature with different kinds of stress, different measurements and different time schedules. Restraint or ether stress induced secretion of PRL involves 5-HT2 and 5-HT3 receptors, whereas the ACTH secretion is mediated via 5-HT1A, 5-HT2A and 5-HT2C receptors. In the present study restraint stress increased AVP secretion, but opposite findings has reported possibly due to differences in the stress procedure. The 5-HT2, 5-HT3 and 5-HT4 receptor is involved in the AVP response to restraint whereas the OT response involves the 5-HT1A and the 5-HT2 receptor. The 5-HT2 receptor is involved in the OT response to dehydration or haemorrhage, whereas the AVP responses to these stressors probably do not involve 5-HT. It can be concluded that 5-HT is involved in basal and stress-induced regulation of PRL, ACTH, AVP and oxytocin mainly via the 5-HT2A+2C receptors but other receptors are also important but differs from hormone to hormone. Serotonin affect the secretion of CRH and ACTH both at the hypothalamic, pituitary portal and pituitary gland level, and possibly also at the adrenal level.     

Electrochemical analysis of hypothalamic serotonin metabolism accompanied by immobilization stress in rats

The effects of stress on serotonin metabolism in the lateral hypothalamic area (LHA) were investigated. Differential pulse voltammetry with a carbon fiber electrode was used to measure 5-hydroxyindoleacetic acid (5-HIAA), the metabolic product of the serotonin (5-HT). High-performance liquid chromatography with electrochemical detection was also used to analyze these compounds in the cerebrospinal fluid (CSF). The peak in voltammogram at an oxidation potential of +230 mV (P3) was identified as 5-HIAA by pharmacological manipulations that are known to affect 5-HT metabolism. A significant increase in 5-HIAA concentration in the LHA was detected after immobilization. An intraperitoneal injection of 5-hydroxytryptophan (5-HTP; a precursor of 5-HT) increased the height of P3, and injection of pargyline prevented the effect of 5-HTP during the course of increasing P3. These results support our previous conclusion that immobilization-induced anorexia might be mediated through activation of serotonergic mechanisms in the LHA.