RU 24969-induced emesis in the cat: 5-HT1 sites other than 5-HT1A, 5-HT1B or 5-HT1c implicated

RU 24969 was administered s.c. to cats and found to elicit emesis with a maximally effective dose of 1.0 mg/kg. 5-Methoxytryptamine was found to have lower efficacy and to produce a higher incidence of non-specific effects while trifluoromethylphenylpiperizine (TFMPP) was devoid of emetic effects. The emesis elicited by 1.0 mg/kg of RU 24969 was not altered by pretreatment with phentolamine, haloperidol, yohimbine or (−)-propranolol, indicating that catecholamines played no role in this response. The emesis was prevented by metergoline and methysergide but not by ketanserin, cyproheptadine, mesulergine, ICS 205 930, methiothepin, trimethobenzamide or BMY 7378. An indirect arguments is presented that implicates a role for 5-HT_1D sites. This conclusion must remain tentative until drugs selective for this site are synthesized and tested. The emesis was also prevented by 8-hydroxy-2-(di-n-propylamine)tetralin (8-OH-DPAT), confirming that this drug has a general antiemetic effect in cats.     

Bradykinin potentiates 5-HT3 receptor-mediated current in rat trigeminal ganglion neurons

AIM: To explore the modulatory effect of bradykinin (BK) on 5-HT(3 )receptor-mediated current in trigeminal ganglion (TG) neurons in rats. METHODS: The whole-cell patch-clamp technique was used to record 5-HT-activated currents (I(5-HT)) in neurons freshly dissociated from rat TG. Drugs were applied by rapid solution exchange. RESULTS: The majority of the neurons examined responded to 5-HT applied externally with an inward current (76.3%, 74/97) that could be blocked by the 5-HT(3 )receptor antagonist, ICS-205,930 (10(-6) mol/L). In 66 of the 74 cells sensitive to 5-HT (89.2%), pretreatment for 30 s with BK (10(-6)-10(-10) mol/L) could potentiate I(5-HT) with the maximal modulatory effect occurring at 10(-7) mol/L BK (71.6%+/-4.9%). BK shifted the 5-HT concentration-response curve upwards with an increase of 68.9%+/-7.2% in the maximal current response, but with no significant change in the EC(50) value (19.1+/-3.2 mumol/L vs 20.9+/-3.5 micromol/L; t-test, P>0.05; n=8). BK potentiated I(5-HT) in a holding potential-independent manner and did not alter the reverse potential of I(5-HT). This BK-induced potentiation of I(5-HT) was almost completely blocked by Hoe 140 (5*10(-7) mol/L), a selective B2 BK receptor antagonist, and was removed after intracellular dialysis of GF-109203X (2 micromol/L), a selective protein kinase C (PKC) inhibitor, with the re-patch clamp. CONCLUSION: Pre-application of BK exerts an enhancing effect on I(5-HT) via a PKC-dependent pathway in rat TG neurons, which may explain the peripheral mechanism of pain and hyperalgesia caused by, for example, tissue damage and inflammation.     

Generation of a selective 5-HT3B subunit-recognising polyclonal antibody; identification of immunoreactive cells in rat hippocampus

The present study generated a polyclonal antibody (AP86/3) that recognises a peptide sequence of the h5-HT_3B receptor subunit. Western blot analysis of homogenates prepared from cell lines expressing either homomeric (h5-HT_3A) or heteromeric (h5-HT_3A/3B) receptors, as well as immunocytochemical studies with the same cell lines, indicated that AP86/3 recognised, selectively, the 5-HT_3B subunit. Immunohistochemical labelling was also apparent in cells in the rat hippocampus that displayed the distribution and morphology of interneurones.     

Selective destruction of the serotonergic fibers of the fornix-fimbria and cingulum bundle increases 5-HT1 but not 5-HT2 receptors in rat midbrain

Selected and localized lesions of serotonergic (5-HT) neurons were made by microinjection of 5,7-dihydroxytryptamine (5,7-DHT), after pretreatment with desipramine, into the cingulum bundle and fornix-fimbria; these are the major serotonergic hippocampal inputs from the median raphe nucleus. Two weeks after the lesion, the binding of [³H]5-HT (5-HT₁ receptor) was determined in the hippocampus which receives the afferent terminals and, in addition, in the septum/hypothalamus and midbrain from where the fibers originate. Scatchard analysis showed there was no significant change in binding parameters in the hippocampus; however, a significant increase was observed in the B_max in the midbrain (38%) with no change in the K_D. The caudate which receives 5-HT inputs via other 5-HT tracts was not affected by the lesion. The changes in 5-HT₁ receptor number or affinity were not observed 6 days or 5 weeks after the lesion. The binding of the ligands [³H]spiroperidol and [³H]ketanserin to the 5-HT₂ receptor population was also determined in the same brain areas; no changes in receptor binding occurred two weeks after the lesion. These experiments demonstrate that a selective lesion of the serotonergic system can increase 5-HT₁ receptors in the midbrain, which contains the serotonin cell bodies. In addition, as 5-HT₂ binding is not altered, this further supports the hypothesis that 5-HT₁ and 5-HT₂ receptors are distinct populations of receptors.     

某院120例5-HT3受体拮抗剂用药分析

目的： 了解某院5-HT₃受体拮抗剂在临床上的应用情况,促进此类药物在临床上的合理使用。方法： 采用回顾性的分析方法,在2018年1-12月使用5-HT₃受体拮抗剂的住院病历中随机抽取120份,就患者的性别、年龄、药品适应证、用法用量、疗程、联合用药等数据应用Excel软件进行统计和分析。结果： 在120份住院病历中合理应用5-HT₃受体拮抗剂的病历数有20份,用药合格率仅有16.67%;不合理应用的病历数有100份,不合理用药体现在以下几个方面：用法用量不适宜（75份,75%）,联合用药不适宜（13份,13%）,疗程过长（8份,8%）,适应证不适宜（4份,4%）。结论： 5-HT₃受体拮抗剂不合理应用情况较为严重,尤其是超剂量用药问题较多,临床医师、临床药师和医院相关部门应加强5-HT₃受体拮抗剂的医嘱点评以及采购管理,共同促进合理用药。     

Distribution and characterization of the [H]granisetron-labelled 5-HT3 receptor in the human forebrain

The present study has demonstrated the distribution of [³H]granisetron-labelled 5-HT₃ receptors in the human forebrain with relatively high levels of this receptor in homogenates of hippocampus, caudate nucleus, putamen, nucleus accumbens and amygdala. Lower levels of 5-HT₃ receptors were found in other brain regions and the cervical vagus nerve. Pharmacological characterization of the labelled 5-HT₃ receptor in human putamen homogenates identified a relatively low affinity for d-tubocurarine compared to the 5-HT₃ receptor in NG108-15 neuroblastoma-glioma cell homogenates. In contrast, the affinities of 19 other 5-HT₃ receptor ligands were not significantly different for the [³H]granisetron-labelled receptor in these two preparations. Such findings indicate that the human putamen 5-HT₃ receptor displays a unique pharmacology which may have significance given the reported clinical potential of compounds active at this receptor when assessed in animal models of disease.     

2008—2010年复旦大学附属肿瘤医院5-羟色胺3受体阻断剂临床应用分析

目的:统计我院2008—2010年临床5-羟色胺3(5-HT3)受体阻断剂使用情况和发展趋势,探讨合理使用要点。方法:对我院3年来5-HT3受体阻断剂使用情况进行回顾性分析,统计药品的销售数量、金额、类别,分析临床用药趋势。结果:5-HT3受体阻断剂总体用量呈快速增长,品种使用显示出明显的变化趋势。结论:3年来5-HT3受体阻断剂总体用量增长,长半衰期品种受临床欢迎。     

Effects of granisetron, a 5-HT3 receptor antagonist, on morphine-induced potentiation of brain stimulation reward

Using the curve-shift method, we studied the effects of four doses (0.003, 0.03, 0.3 and 3 mg/kg, s.c.) of granisetron (endo-N-(9-methyl-9-azabicyclo[3.3.1]non-3-yl)-1-methyl-1H-indazole-3-carboxamide hydrochloride), a selective 5-hydroxytryptamine₃ (5-HT₃) receptor antagonist, on the potentiation of brain stimulation reward by microinjection of 2.5 μg/0.25 μl of morphine sulphate (7,8-didehydro-4,5-epoxy-17-methylmorphinan-3,6-diol sulphate) into the ventral tegmental area. As previously reported, morphine produced a significant reduction in reward threshold without altering maximal rates of responding. Granisetron attenuated the potentiating effect of morphine at the highest dose and failed to alter reward threshold or maximal rates of responding when given alone, except at the lowest dose where a small and statistically significant increase in threshold was found. These results provide additional evidence that 5-HT₃ receptor antagonists may reduce the rewarding effect of opiates and do not impair the ability to produce operant responses. The weak attenuation observed with granisetron alone suggests that 5-HT₃ receptors are unlikely to constitute an important influence on the directly stimulated reward-relevant pathway(s).     

比较5-羟色胺3受体拮抗剂在预防剖宫产术中低血压的效果及对母婴的影响

目的 比较脊柱麻醉前静注不同5-羟色胺3(5-HT3)受体拮抗剂预防脊柱麻醉下剖宫产术中低血压的效果以及对产妇和胎儿的影响.方法 拟择期在脊柱麻醉下行剖宫产术的单胎足月妊娠产妇120例,按随机数字表法分为S组、T组、G组、A组,每组30例,分别在脊柱麻醉前5 min静脉推注生理盐水5 mL (S组),托烷司琼5 mg(T组)、格拉司琼3 mg(G组)、阿扎司琼10 mg(A组)(所有药物使用生理盐水稀释至5 mL).从脊柱麻醉鞘内注药2 min后开始,每隔2 min测量并记录一次血压、心率和血氧饱和度(SpO2)直至鞘内注药30 min.胎儿娩出后即刻取胎儿脐动脉和脐静脉的血标本行血气分析.结果 G组产妇术中低血压和恶心的发生率明显低于S组(P<0.05),G组脐静脉血的二氧化碳分压[p(CO2)]明显低于S组(P<0.05),T组和A组的恶心发生率明显低于S组(P<0.05).G组和A组脐静脉血的pH值明显高于S组而碳酸氢根离子(HCO-3)浓度明显低于S组(P<0.05),T组的HCO-3浓度也明显低于S组(P<0.05).G组产妇术中收缩压最大下降值明显小于S组(P<0.05).结论 脊柱麻醉前静注5-HT3受体拮抗剂可以一定程度上减少产妇脊柱麻醉后血压的下降以及产妇低血压和恶心的发生,从而改善脐静脉的酸碱状态.     

Effects of 5-HT3 receptor antagonists on models of acute and delayed emesis induced by cisplatin in the ferret

The emetic profile of action of cisplatin 5 and 10 mg/kg i.p. was investigated in the ferret over a 72 and 24 hr period respectively. The 5-HT₃ receptor antagonists ondansetron and alosetron markedly antagonized or abolished the emesis during the “acute phase” and, whilst antagonizing the emesis during the delayed phase, also revealed a 5-HT₃ receptor antagonist resistant component. These cisplatin paradigms may provide models relevant to the study of acute and delayed emesis induced by cisplatin in man.     

5-HT2受体介导大鼠DRG神经元膜GABA-激活电流的增强作用

目的探讨5-HT对大鼠DRG神经元膜GABA-激活电流的调节作用及其机制。方法在新鲜分离的大鼠DRG神经元标本上，以全细胞膜片钳技术记录膜电流，用排管快速换液装置行胞外给药，以胞内透析技术分析信号转导途径。结果给予GABA可使多数受检细胞产生浓度依赖性内向电流(I_GABA)。预加5-HT，可使I_GABA增加。此效应可被5-HT₂受体特异性激动剂α-methyl-5-HT(1×10^-6 mol·L^-1)所模拟，被5-HT₂受体选择性拮抗剂cyproheptadine所阻断。在部分细胞，5-HT本身可引起由5-HT₃受体介导的快速内向电流，但并未发现该电流与5-HT对I_GABA的增强作用有必然的联系。从GABA激活电流的量效曲线可见，预加5-HT后和对照曲线相比，阈浓度不变、EC₅₀值相近，I_GABA最大值增加33.6%。胞内透析GDP-β-S或H-7可取消5-HT增强I_GABA的效应，而透析H-9无效。结论5-HT可增强GABA-激活电流，其机制为5-HT₂受体激活后通过PKC引起GABA_A受体胞内磷酸化所致。     

Molecular modeling of 5-HT3 receptor ligands

Ligands of various chemical classes (e.g., indoles, indazoles, benzamides, carbazoles, and quinolines) have demonstrated high affinity for the 5-HT₃ receptor in radiolabeled ligand-binding studies, and have shown 5-HT₃ receptor antagonistic activity in functional assays which utilize the excitatory effects of 5-HT on enteric neurons and autonomic afferents. Several 5-HT₃ antagonists are currently being evaluated for potential use in the treatment of migraine, schizophrenia, and anxiety, and a few have already demonstrated high efficacy as antiemetics in cancer chemotherapy. The purpose of this presentation is to highlight the significant structure-affinity relationships (SAFIR) and common geometrical features among 5-HT₃ receptor ligands, and to describe the three-dimensional pharmacophore for the 5-HT₃ recognition site derived from computational techniques. The chemical template containing the recognition elements (functional groups) for the 5-HT₃ receptor are: an aromatic or heteroaromatic ring system, a coplanar carbonyl group, and a nitrogen center, interrelated by well-defined distances. Two “binding shapes” or “active shapes” for 5-HT₃ ligands have been identified from detailed conformational analyses.     

Effect of chronic administration of selective 5-hydroxytryptamine and noradrenaline uptake inhibitors on a putative index of 5-HT2C/2B receptor function

Chronic treatment with selective 5-HT reuptake inhibitors (SSRI) are therapeutic in obsessive compulsive disorder, depression, anxiety, bulimia nervosa and migraine. In the present study the possibility that SSRI's act by desensitizing 5-HT_2C/5-HT_2B receptors was assessed using a putative in vivo model of 5-HT_2C/5-HT_2B receptor function, mCPP-induced hypolocomotion. mCPP (2,4 and 6 mg/kg i.p. 20 min pretest) reduced locomotion and rears in rats treated acutely or chronically with saline. Acute oral administration of the SSRI's fluoxetine (10 mg/kg), paroxetine (10 mg/kg), or clomipramine (70 mg/kg) or the noradrenaline reuptake inhibitor, desipramine (10 mg/kg), all 1 hr pretest, did not prevent mCPP-induced hypolocomotion. In contrast, chronic treatment with the SSRI's paroxetine and fluoxetine (both 10 mg/kg p.o. daily × 21 days), significantly attenuated the effect of mCPP (4 and 6 mg/kg i.p.) on locomotion and rears 24 hr after the last pretreatment dose. Chronic clomipramine (70 mg/kg p.o. daily × 21 days) also significantly attenuated the effect of mCPP (4 mg/kg i.p.) on rears and tended to reduce the hypolocomotor response. However, chronic treatment with desipramine, (10 mg/kg p.o.daily × 21) had no effect on any of the parameters measured. As chronic fluoxetine and paroxetine did not reduce brain mCPP levels (determined by HPLC 30 min after 4 mg/kg i.p.) the results suggest that chronic SSRI's, but not desipramine, reduce 5-HT_2C/5-HT/_2B receptor responsivity. If this occurs in man, it may mediate or contribute to their reported therapeutic efficacy in depression, anxiety, bulimia, migraine and alcoholism. It may also be of particular relevance to their unique efficacy in OCD.     

Antidepressant-like responses to the combined sigma and 5-HT1A receptor agonist OPC-14523

The antidepressant-like activity of a novel compound, OPC-14523, was investigated in comparison with the conventional antidepressants, fluoxetine and imipramine. OPC-14523 bound with nanomolar affinities to sigma receptors (IC₅₀=47–56 nM), the 5-HT_1A receptor (IC₅₀=2.3 nM), and the 5-HT transporter (IC₅₀=80 nM). OPC-14523 inhibited the in vitro reuptake of ³H-5-HT (IC₅₀=27 nM), but it showed very weak inhibitory activity on ³H-NE and ³H-DA reuptake. OPC-14523 did not inhibit MAO A or B activities or muscarinic receptors. A single oral administration of OPC-14523 produced a marked antidepressant-like effect in the forced swimming test (FST) with rats (ED₅₀=27 mg/kg) and mice (ED₅₀=20 mg/kg) without affecting the general locomotor activity. In contrast, fluoxetine and imipramine each required at least four days of repeated dosing to show this activity. The acute activity of OPC-14523 was blocked by pretreatment with the sigma receptor antagonist NE-100 or the selective 5-HT_1A receptor antagonist WAY-100635. The induction of flat body posture by OPC-14523 was blocked by the selective 5-HT_1A receptor antagonist NAN-190, and forebrain 5-HT biosynthesis was attenuated by OPC-14523 at behaviorally effective doses. In contrast, OPC-14523, unlike fluoxetine, failed to inhibit 5-HT reuptake at oral doses below 100 mg/kg. Thus, the acute antidepressant-like action of OPC-14523 is achieved by the combined stimulation of sigma and 5-HT_1A receptors without inhibition of 5-HT reuptake in vivo.     

5-HT3 receptors augment neuronal, cholinergic contractions in guinea pig trachea European Journal of Pharmacology, 234 (1993) 109–112

Serotonin (5-HT) and the selective 5-HT₃ receptor agonist, 2-methyl-5-hydroxytryptamine enhanced electrical field stimulated contractions of the isolated guinea pig trachea. 5-HT (EC₅₀ = 3.5 μM) was twice as potent as 2-methyl-5-hydroxytryptamine (EC₅₀ = 7.4 μM). The effects of 5-HT and 2-methyl-5-hydroxytryptamine were antagonized by the selective 5-HT₃ receptor antagonist, zacopride (apparent pA₂ = 7.60 against 2-methyl-5-hydroxytryptamine). 2-Methyl-5-hydroxytryptamine (10 μM) had no effect on contractile responses to exogenous acetylcholine. Furthermore, the increase in electrical field stimulated contraction by 2-methyl-5-hydroxytryptamine was unchanged by hexamethonium (100 μM) but contractions were blocked by atropine (1 μM). These results suggest that excitatory 5-HT₃ receptors exist on postganglionic cholinergic nerves in the isolated guinea pig trachea.     

Selective labelling of 5-HT7 receptor recognition sites in rat brain using [H]5-carboxamidotryptamine

The aim of the present study was to establish a radioligand binding assay to selectively label the native 5-HT₇ receptor expressed in rat brain. In rat whole brain (minus cerebellum and striatum) homogenate, (±)-pindolol (10 μM)-insensitive [³H]5-CT ([³H]5-carboxamidotryptamine; 0.5 nM) specific binding (defined by 5-HT, 10 μM) displayed a pharmacological profile similar to the recombinant 5-HT₇ receptor, although the Hill coefficients for competition curves generated by methiothepin, ritanserin, sumatriptan, clozapine and pimozide were significantly less than unity. In homogenates of rat hypothalamus, (±)-pindolol (10 μM)-insensitive [³H]5-CT recognition sites also resembled, pharmacologically, the 5-HT₇ receptor, although pimozide still generated Hill coefficients significantly less than unity. Subsequent studies were performed in the additional presence of WAY100635 (100 nM) to prevent [³H]5-CT binding to residual, possibly, 5-HT_1A sites. Competition for this [³H]5-CT binding indicated the labelling in whole rat brain homogenate of a homogenous population of sites with the pharmacological profile of the 5-HT₇ receptor. Saturation studies also indicated that (±)-pindolol (10 μM)/WAY 100635 (100 nM)-insensitive [³H]5-CT binding to homogenates of whole rat brain was saturable and to an apparently homogenous population of sites which were labelled with nanomolar affinity (B_max=33.2±0.7 fmol mg⁻¹ protein, pK_d=8.78±0.05, mean±S.E.M., n=3). The development of this 5-HT₇ receptor binding assay will aid investigation of the rat native 5-HT₇ receptor.     

5-HT1A receptor-mediated inhibition in the hippocampus of the alert rat — effects of repeated gepirone treatment

The effects of acute and repeated treatment with the 5-HT_1A receptor ligand gepirone on hippocampal excitatory synaptic transmission were investigated. Recordings of the electrically evoked field population excitatory postsynaptic potentials (e.p.s.p.s.) were made in the stratum radiatum of the CA1 region of the dorsal hippocampus of alert male Wistar rats. Acute injection of gepirone reduced the e.p.s.p. amplitude in a transient dose-dependent (0.5 – 10 mg/kg, i.p.) manner. This effect was blocked by the 5-HT_1A receptor antagonist MDL 73005EF (8-[2,3-dihydro-1,4-benzodioxin-2-yl methylaminoethys]-8-azaspirol[4,5]decane-7,9-dione methyl sulphonate, 2 mg/kg, i.p.). Gepirone (1 mg/kg per day, i.p.) administered for 7 days produced a gradual reduction in the daily pre-injection baseline e.p.s.p. amplitude coupled with a concomitant reduction of the acute response to the drug. The chronic baseline reduction was transiently reversed by the 5-HT_1A receptor antagonist spiroxatrine and complete recovery to pretreatment levels was observed 48 h after the last gepirone dose. The data indicate that with repeated administration, a prolongation and enhancement of the 5-HT_1A receptor-mediated reduction in the e.p.s.p. by gepirone occurs. This delayed effect may contribute to the slow onset of therapeutic action of gepirone.     

5-HT3 receptor antagonists inhibit the response of κ oploid receptors in the morphine-reduced straub tail

We used the morphine-induced Straub tail to examine the actions of a 5-HT₃ receptor antagonist and κ opioid receptor agonist. The κ opioid receptor agonist, U-50,488H (4–16 mg/kg i.p.), produced a dose-related inhibition of the tail elevation induced by morphine (10 mg/kg s.c.) in ICR male mice. ICS-205-930 (3 and 10 mg/kg i.p.) and zacopride (0.3 and 1 mg/kg i.p.), 5-HT₃ receptor antagonists, attenuated the inhibitory effect of U-50,488H in a dose-dependent manner. ICS-205-930 and zacopride did not inhibit the morphine-induced Straub tail. These observations suggest that the actions of κ opioid receptors may be modulated by 5-HT³ receptors in the morphine-induced Straub tail.     

Effects of selective activation of the 5-HT1B receptor with CP-94,253 on sleep and wakefulness in the rat

The effects of the 5-HT_1B receptor agonist CP-94,253 were compared with those of the mixed β-adrenoceptor and 5-HT_1A/B receptor antagonist (±)pindolol in rats implanted for chronic sleep recordings. CP-94,253 (5.0–10.0 mg/kg) significantly increased waking and reduced slow wave sleep (SWS) and REM sleep (REMS). At 2.0–4.0 mg/kg (±)pindolol reduced REMS. Pretreatment with (±)pindolol (2.0–4.0 mg/kg) reversed the effect of CP-94,253 on waking and SWS, while REMS remained suppressed. It is suggested that the 5-HT_1B receptor together with other 5-HT receptor subtypes may have a direct regulatory action on sleep and waking in the rat.     

Alcohols potentiate ion current mediated by recombinant 5-HT3RA receptors expressed in a mammalian cell line

The effect of acute exposure to alcohols on ion current mediated by recombinant 5-HT₃RA receptors transiently expressed in human embryonic kidney 293 cells was investigated. Cells transfected with 5-HT₃RA cDNA expressed receptors with pharmacological and functional properties similar to those of native 5-HT₃ receptors. Potentiation of receptor-mediated cation current was observed in the presence of ethanol (10–100 mM), butanol (0.1–20mM), isopentanol (0.01–25 mM) and trichloroethanol (0.5–25 mM). Potentiation increased in a concentration-dependent manner until saturation was achieved for all alcohols tested. The maximal efficacies of potentiation differed among the alcohols with isopentanol > BUTANOL = trichloro-ethanol > ethanol. Potentiation by butanol and isopentanol appeared to show acute tolerance such that the percent increase in current amplitude was largest upon the first of a series of alcohol applications and decreased during subsequent applications. The effect of ethanol was variable with potentiation occurring in 74% of cells examined, but not in the remaining cells. These observations indicate that the potentiating action of alcohols is similar in recombinant receptors to that previously observed in neuroblastoma cells and neurons expressing native receptors. These findings indicate that this recombinant system is suitable for studying the molecular basis of alcohol actions on the 5-HT₃ receptor.