PM2.5 upregulates rat mesenteric arteries 5‐HT2A receptor via inflammatory‐mediated mitogen‐activated protein kinases signaling pathway

Fine particulate matter (PM_2.5) is an important environmental risk factor for cardiovascular diseases. However, little is known about the effects of PM_2.5 on arteries. The present study investigated whether PM_2.5 alters 5‐hydroxytryptamine (5‐HT) receptor expression and inflammatory mediators on rat mesenteric arteries, and examined the underlying mechanisms. Isolated rat mesenteric arteries segments were cultured with PM_2.5 in the presence or absence of ERK1/2, JNK, and p38 pathway inhibitors. Contractile reactivity was monitored by a sensitive myograph. The expression of 5‐HT_2A/1B receptors and inflammatory mediators were studied by a real‐time polymerase chain reaction and/or by immunohistochemistry. The phosphorylation of mitogen‐activated protein kinases (MAPK) pathway was detected by Western blot. Compared with the fresh or culture alone groups, 1.0 μg/mL PM_2.5 cultured for 16 hours significantly enhanced contractile response induced by 5‐HT and increased 5‐HT_2A receptor mRNA and protein expressions, indicating PM_2.5 upregulates 5‐HT_2A receptor. SB203580 (p38 inhibitor) and U0126 (ERK1/2 inhibitor) significantly decreased PM_2.5‐induced elevated contraction and mRNA and protein expression of 5‐HT_2A receptor. Cultured with PM_2.5 significantly increased the mRNA expression of inflammatory mediators (NOS2, IL‐1β, and TNF‐α), while SB203580 decreased mRNA expression level of NOS2, IL‐1β, and TNF‐α. SP600125 (JNK inhibitor) decreased mRNA expression level of TNF‐α and IL‐1β. After PM_2.5 exposure, the phosphorylation of p38 and ERK1/2 protein were increased. SB203580 and U0126 inhibited the PM_2.5 caused increased phosphorylation protein of p38 and ERK1/2. In conclusion, PM_2.5 induces inflammatory‐mediated MAPK pathway in artery which subsequently results in enhanced vascular contraction responding to 5‐HT via the upregulated 5‐HT_2A receptors.     

A novel method for the synthesis of carbon‐14‐labeled N‐[3‐(1‐methyl‐4‐piperidinyl)‐1H‐pyrrolo[3,2‐b]pyridin‐5‐yl]propanamide and its use in quantitative whole‐body autoradiography studies

Sumitriptan ( 1 ), a non‐selective 5‐HT_1B/1D agonist is an effective therapeutic agent for the acute treatment of migraine, but it is contraindicated for use in patients with known heart disease. The first Selective Serotonin One F Receptor Agonist (SSOFRA), 5‐(4′‐fluorobenz‐amido)‐3‐(N‐methyl‐piperidin‐4‐yl)‐1H‐indole ( 2 ) was demonstrated to be clinically useful in the treatment of migraine. Although 2 exhibited high affinity for the 5‐HT_1F receptor as well as high selectivity for the 5‐HT_1F receptor relative to 5‐HT_1B and 5‐HT_1D receptors, it demonstrated appreciable affinity for the 5‐HT_1A receptor. Subsequently, a program was launched to discover SSOFRA's with improved selectivity over other 5‐HT₁ receptor subtypes. As a result of these efforts, N‐[3‐(1‐methyl‐4‐piperidinyl)‐1H‐pyrrolo[3,2‐b]pyridin‐5‐yl]propanamide ( 3 ) was found to possess greater than 100‐fold selectivity over 5‐HT_1A, 5‐HT_1B and 5‐HT_1D receptors. Pursuant to a potential clinical investigation of 3 , its carbon‐14‐labeled isotopomer has been prepared by a circuitous route from unlabeled 3 and used in quantitative whole‐body autoradiography studies in rats. The results of these efforts are reported herein. Copyright © 2005 John Wiley & Sons, Ltd.     

Pharmacological evidence that 5‐HT1D activation induces renal vasodilation by NO pathway in rats

5‐HT is a powerful vasoconstrictor substance in renal vasculature (mainly by 5‐HT₂ activation). Nevertheless, 5‐HT is notable for its dual cardiovascular effects, producing both vasodilator and vasoconstrictor actions. This study aimed to investigate whether, behind the predominant serotonergic vasoconstrictor action, THE 5‐HT system may exert renal vasodilator actions, and, if so, characterize the 5‐HT receptors and possible indirect pathways. Renal perfusion pressure (PP), systemic blood pressure (SBP) and heart rate (HR) measurement in in situ autoperfused rat kidney was determined in phenylephrine infused rats. Intra arterial (i.a.) bolus administration of 5‐HT (0.00000125–0.1 μg/kg) decreased renal PP in the presence of a phenylephrine continuous infusion (phenylephrine‐infusion group), without modifying SBP or HR. These vasodilator responses were potentiated by 5‐HT₂ antagonism (ritanserin, 1 mg/kg i.v.), whereas the responses were abolished by 5‐HT_1/7 antagonist (methiothepin, 100 μg/kg i.v.) or 5‐HT_1D antagonist (LY310762, 1 mg/kg i.v.). The i.a. administration (0.00000125 to 0.1 μg/kg) of 5‐CT or L‐694,247 (5‐HT_1D agonist) mimicked 5‐HT vasodilator effect, while other agonists (1‐PBG, α‐methyl‐5‐HT, AS‐19 (5‐HT₇), 8‐OH‐DPAT (5‐HT_1A) or CGS‐12066B (5‐HT_1B)) did not alter baseline haemodynamic variables. L‐694,247 vasodilation was abolished by i.v. bolus of antagonists LY310762 (5‐HT_1D, 1 mg/kg) or L‐NAME (nitric oxide, 10 mg/kg), but not by i.v. bolus of indomethacin (cyclooxygenase, 2 mg/kg) or glibenclamide (ATP‐dependent K⁺ channel, 20 mg/kg). These outcomes suggest that 5‐HT_1D activation produces a vasodilator effect in the in situ autoperfused kidney of phenylephrine‐infusion rats mediated by the NO pathway.     

5‐HT modulates the rat mesenteric vasopressor outflow by 5‐HT1D sympatholytic receptors

5‐hydroxytryptamine (5‐HT) modulates noradrenergic activity in different cardiovascular territories, but its effect on the mesenteric vasopressor outflow has not yet been clarified. This study investigated the in vivo serotonergic influence, characterizing 5‐HT receptors implicated, in sympathetic innervation of mesenteric vasculature. Wistar rats were anaesthetised and prepared for the in situ autoperfused rat mesentery, monitoring systemic blood pressure (SBP), heart rate (HR) and mesenteric perfusion pressure (MPP). Electrical stimulation of mesenteric sympathetic nerves resulted in frequency‐dependent increases in MPP (9 ± 1.6, 25.7 ± 3.9 and 60.2 ± 5 mmHg for 2, 4 and 8 Hz, respectively), without altering SBP or HR. 5‐HT (1‐25 μg/kg), 5‐carboxamidotryptamine (5‐HT_1/7 agonist; 25 μg/kg) or L‐694,247 (5‐HT_1D agonist; 1‐25 μg/kg) i.a. bolus inhibited vasopressor responses by mesenteric nerves electrical stimulation, unlike i.a. bolus of agonists 8‐OH‐DPAT (5‐HT_1A), CGS‐12066B (5‐HT_1B), BRL 54443 (5‐HT_1e/1F), α‐methyl‐5‐HT (5‐HT₂), 1‐PBG (5‐HT₃), cisapride (5‐HT₄) or AS‐19 (5‐HT₇) (25 μg/kg each). Interestingly, i.a. L‐694,247 (25 μg/kg) also reduced the exogenous norepinephrine‐induced vasoconstrictions. Pretreatment with selective 5‐HT_1D receptor antagonist, LY310762 (1 mg/kg, i.v.), completely abolished L‐694,247‐ and 5‐HT‐induced mesenteric sympathoinhibition. Furthermore, ELISA analysis confirmed 5‐HT_1D receptors expression in mesenteric artery. These findings suggest that serotonergic mechanisms‐induced sympathoinhibition of mesenteric noradrenergic outflow is mediated by pre and/or postjunctional 5‐HT_1D receptors.     

Stimulation of 5‐HT4 receptor enhances differentiation of mouse induced pluripotent stem cells into neural progenitor cells

Activation of serotonin (5‐hydroxytryptamine; 5‐HT) receptors plays a role in adult neurogenesis and differentiation of neural progenitor cells (NPC). Herein, we examined the involvement of 5‐HT receptors in the differentiation of mouse induced pluripotent stem (iPS) cells into NPC. To induce embryoid body (EB) formation, mouse iPS cells were cultured on ultralow‐attachment dishes. All‐trans retinoic acid (ATRA; 1 μmol/L) and/or 5‐HT (0.03 or 0.1 μmol/L) was added to the EB cultures for 4 days and then EB plated on gelatin‐coated plates were cultured for 7 or 14 days. Immunofluorescence staining revealed that mouse iPS cells expressed both 5‐HT_2A and 5‐HT₄ receptors and, to a lesser extent, 5‐HT_1A receptors. Treatment with 5‐HT significantly enhanced the ATRA‐induced expression of nestin, a specific marker for NPC, and phosphorylation of cAMP response element‐binding protein (CREB). Pretreatment of EB cultures with either 1 μmol/L GR113808 (a selective 5‐HT₄ receptor antagonist) or 1 μmol/L H89 (a protein kinase (PKA) inhibitor) significantly inhibited these effects of 5‐HT. These findings suggest that stimulation of 5‐HT₄ receptors may enhance ATRA‐induced neural differentiation of mouse iPS cells through activation of PKA and CREB.     

Involvement of 5‐HT2A Receptors in the Serotonin (5‐HT) Syndrome caused by Excessive 5‐HT Efflux in Rat Brain

Abstract: Previous studies have demonstrated that serotonin (5‐HT) syndromes, particularly for the malignant cases, can be alleviated by ice water mists, cooling blankets and many other external cooling measures. In this study, we tested the hypothesis that external cooling measures reduce the responsivity of 5‐HT_2A receptors to excessive 5‐HT efflux, which may be a possible mechanism underlying the treatment of serotonin syndrome. To test this, rat experiments were carried out in the standard and cool ambient temperature (T_amb) by administration of the 5‐HT precursor 5‐hydroxy‐l ‐tryptophan combined with the monoamine oxidase inhibitor clorgyline. The first set of experiments was to assess severity of the syndromes by measuring body temperature responses. Consistent with the hypothesis, we found that the syndrome was malignant at the standard T_amb of 22°C but alleviated at 12 or 6°C, these results being similar to those in rats pre‐treated with the 5‐HT_2A receptor antagonist ketanserin. The second set of experiments was to utilize microdialysis to determine the relationship between the syndrome severity and 5‐HT levels at the above‐mentioned T_amb. We found that excessive 5‐HT efflux consisted of primary and secondary components through two distinct mechanisms. Furthermore, the secondary component efflux, which can be ascribed to 5‐HT_2A receptor activation, was proportionally reduced at the cool T_amb of 12 and 6°C. In conclusion, results of this study support the hypothesis that cooling T_amb reduces the functional activity of 5‐HT_2A receptors, thus alleviating the malignant syndrome.     

5-HT_(2B)受体阻断剂对去甲肾上腺素诱导的肥厚心肌组织中心肌细胞凋亡的影响

目的观察5-HT2B受体阻断剂对去甲肾上腺素(NE)诱导的肥厚心肌组织中心肌细胞凋亡的影响。方法雄性SD大鼠24只,随机分为3组,每组8只,分别为对照组,肥厚组、实验组。采用腹腔注射NE(1.5 mg/kg,2次/d,28 d)的方法建立心肌肥厚动物模型,自第15天起实验组腹腔注射SB204741(5-HT2B受体阻断剂)2 mg/kg,2次/d,连续注射14 d。对照组腹腔注射相同体积的生理盐水2次/d,28 d。采用TUNEL法检测各组心肌组织中心肌细胞的凋亡情况,Western blot方法分析Bcl-2、Bax、Caspase-3的表达情况。结果对照组的心肌组织中几乎看不到凋亡的心肌细胞,肥厚组心肌组织中凋亡心肌细胞数量显著增多,同时Bcl-2/Bax表达比例显著降低,Caspase-3的表达显著升高;与肥厚组相比,实验组心肌组织中凋亡心肌细胞的数量显著减少,Bcl-2/Bax表达比例显著升高,Caspase-3的表达显著降低。结论应用5-HT2B受体阻断剂不仅可减轻NE诱导的心肌肥厚的程度,还可通过上调Bcl-2/Bax表达比率、降低Caspase-3的活性抑制心肌细胞的凋亡。     

Selectivity of antagonists for the Cys‐loop native receptors for ACh, 5‐HT and GABA in guinea‐pig myenteric neurons

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The synthetic cathinone psychostimulant α‐PPP antagonizes serotonin 5‐HT2A receptors: In vitro and in vivo evidence

Synthetic cathinones (SCs) are β‐keto analogs of amphetamines. Like amphetamines, SCs target monoamine transporters; however, unusual neuropsychiatric symptoms have been associated with abuse of some SCs, suggesting SCs might possess additional pharmacological properties. We performed radioligand competition binding assays to assess the affinities of nine SCs at human 5‐HT_2A receptors (5‐HT_2AR) and muscarinic M₁ receptors (M₁R) transiently expressed in HEK293 cells. None of the SCs exhibited affinity at M₁R (minimal displacement of [~K_d] [³H]scopolamine up to 10 μM). However, two SCs, α‐pyrrolidinopropiophenone (α‐PPP) and 4‐methyl‐α‐PPP, had low μM K_i values at 5‐HT_2AR. In 5‐HT_2AR–phosphoinositide hydrolysis assays, α‐PPP and 4‐methyl‐α‐PPP displayed inverse agonist activity. We further assessed the 5‐HT_2AR functional activity of α‐PPP, and observed it competitively antagonized 5‐HT_2AR signaling stimulated by the 5‐HT₂R agonist (±)‐2,5‐dimethoxy‐4‐iodoamphetamine (DOI; K_b = 851 nM). To assess in vivo 5‐HT_2AR activity, we examined the effects of α‐PPP on the DOI‐elicited head‐twitch response (HTR) in mice. α‐PPP dose‐dependently blocked the HTR with maximal suppression at 10 mg/kg (P < 0.0001), which is a moderate dose used in studies investigating psychostimulant properties of α‐PPP. To corroborate a 5‐HT_2AR mechanism, we also tested 3,4‐methylenedioxy‐α‐PPP (MDPPP) and 3‐bromomethcathinone (3‐BMC), SCs that we observed had 5‐HT_2AR K_is > 10 μM. Neither MDPPP nor 3‐BMC, at 10 mg/kg doses, attenuated the DOI HTR. Our results suggest α‐PPP has antagonist interactions at 5‐HT_2AR in vitro that may translate at physiologically‐relevant doses in vivo. Considering 5‐HT_2AR antagonism has been shown to mitigate effects of psychostimulants, this property may contribute to α‐PPPs unpopularity compared to other monoamine transporter inhibitors.     

Structure‐Based Identification of Aporphines with Selective 5‐HT2A Receptor‐Binding Activity

Selective blockade of the serotonin 5‐HT_2A receptor is a useful therapeutic approach for a number of disorders, including schizophrenia, insomnia and ischaemic heart disease. A series of aporphines were docked into a homology model of the rat 5‐HT_2A receptor using AutoDock. Selected compounds with high in silico binding affinities were screened in vitro using radioligand‐binding assays against rat serotonin (5‐HT_1A and 5‐HT_2A) and dopamine (D1 and D2) receptors. (R)‐Roemerine and (±)‐nuciferine were found to have high affinity for the 5‐HT_2A receptor (K_i = 62 and 139 nm , respectively), with (R)‐roemerine showing 20‐ to 400‐fold selectivity for the 5‐HT_2A receptor over the 5‐HT_1A, D1 and D2 receptors. Investigation into the ligand–receptor interactions suggested that the selectivity of (R)‐roemerine is due to it having stronger H‐bonding and dipole–dipole interactions with several of the key residues in the 5‐HT_2A receptor‐binding site.     

Synthesis and preliminary PET study of the 5‐HT7 receptor antagonist [11C]DR4446

DR4446 (1‐methyl‐2a‐[4‐(4,5,6,7‐tetrahydrothieno[3,2‐c]pyridin‐5‐yl)butyl]‐2a,3,4,5‐tetrahydro‐1H‐benz[cd]indole‐2‐one) is a potent 5‐HT₇ receptor antagonist (K_i=9.7 nM) with a high selectivity over other 5‐HT family receptors (K_i for 5‐HT_1A: 770 nM; for other 5‐HT receptors: >1000 nM). As a positron emission tomography (PET) tracer for the 5‐HT₇ receptor, [¹¹C]DR4446 was synthesized at high radiochemical purity ( >98%) with specific activity of 73–120 GBq/μmol at the end of synthesis by the alkylation of the desmethyl precursor (1) with [¹¹C]CH₃I in the presence of NaH. A PET study in monkey demonstrated that [¹¹C]DR4446 had good permeability into the brain, and had a specific binding component in the brain regions including the thalamus, possibly an area in the 5‐HT₇ receptors. Metabolite analysis showed that [¹¹C]DR4446 was relatively stable and low percentages of two radio‐labeled metabolites were detected in the plasma of monkey using HPLC. Copyright © 2002 John Wiley & Sons, Ltd.     

Structure–activity relationships of isoeugenol‐based chlorophenylpiperazine derivatives on serotonergic/adrenergic receptor,platelet aggregation,and lipid peroxidation

Three isoeugenol‐based eugenosedin chlorphenylpiperazine derivatives, Eu‐A, Eu‐B, and Eu‐C, were synthesized and tested for their serotonergic, adrenergic antagonist, antioxidant, and anti‐aggregation activities. In radioligand binding assays, all three agents displayed significant binding affinities on α₁, α₂, β₁, 5‐HT_1B, and 5‐HT_2A receptors. In human platelet, they inhibited epinephrine and 5‐HT‐induced aggregation, and in human platelet with α₂ and 5‐HT_2A receptors they had a competitive binding effect. Eu‐B and Eu‐C were more potent than Eu‐A. All compounds had antioxidant effects derived from aryloxypropanolamine. Eu‐ A, Eu‐B, or Eu‐C (1, 3, 5 mg/kg iv) given to normotensive Wistar rats produced a dose‐dependent decrease in mean arterial blood pressure and heart rate and when injected into the cisternum, Eu‐A, Eu‐B, or Eu‐C (0.3, 0.03 µmol) increased blood pressure within 15 min. Pretreatment with any of the three agents inhibited clonidine (38 pmol)‐induced hypotension. In vitro experiments, Eu‐A, Eu‐B, or Eu‐C (1, 10, and 100 µM) competitively antagonized norepinephrine‐, clonidine‐, and 5‐HT (10^?8–10^?4 M)‐induced vasocontraction in isolated rat aorta, and competitively antagonized isoproterenol (10^?8–10^?4 M)‐induced positive inotropic effects in a concentration‐dependent manner in the isolated rat left atrium. In isolated rabbit ear arteries sensitized with 16 mM K⁺, all three agents antagonized 5‐nonyloxytryptamine‐ and 5‐HT‐induced vasocontractions. These findings show that Eu‐A, Eu‐B, and Eu‐C possess functional α₁, α₂, β₁, 5‐HT_1B, and 5‐HT_2A receptor blocking activities. In conclusion, the changes in the position of chloride at phenylpiperazine influenced the serotonergic receptor, adrenoceptor antagonistic activities, but not anti‐aggregation and antioxidant activities. Drug Dev Res 71:1–9, 2010. © 2010 Wiley‐Liss, Inc.     

Human Isolated Coronary Artery Contraction to Sumatriptan Characterised by the Selective 5‐HT1B/1D Receptor Antagonist GR55562

The antimigraine drug, sumatriptan, contracts the human coronary artery both in vivo and in vitro. Because sumatriptan has been associated with cardiac side effects, it is important to characterise the receptor involved in sumatriptan‐induced coronary artery contraction. Using the agonists sumatriptan and 5‐carboxamidotryptamine and the selective 5‐HT_1B/1D receptor antagonist GR55562, we have investigated the involvement of 5‐HT_1B/1D receptors in the contraction of the human isolated coronary artery. Contractions to sumatriptan (pEC₅₀: 6.1±0.2, maximal effect: 21±4% of 100 mM K⁺‐induced contraction) were competitively antagonised by GR55562. The pA₂ of GR55562 (7.40±0.16) was in accord with its reported affinity at the human 5‐HT_1B receptor. Since the contractions to 5‐carboxamidotryptamine did not reach a maximum with the highest concentration used (10 μM), pEC₅₀ values could not be calculated for Schild analysis. However, using the pEC_10%K+ values (negative logarithm of the concentration needed to induce 10% of the contraction to 100 mM K⁺), GR55562 proved a less potent antagonist against 5‐carboxamidotryptamine than against sumatriptan. These results show that sumatriptan contracts the human isolated coronary artery via 5‐HT_1B/1D receptors, most probably the 5‐HT_1B subtype. 5‐Carboxamidotryptamine may contract the human isolated coronary artery, at least partly, via a novel yet to be characterised, receptor.     

5-HT_(2B)受体阻断剂对心肌肥厚大鼠心肌5-HT含量及5-HT_(2B)受体表达的影响

目的观察5-HT2B受体阻断剂对去甲肾上腺素(norepinephrine,NE)诱导的心肌肥厚大鼠心肌中5-羟色胺(5-hydrotriptamine,5-HT)含量及5-HT2B受体表达的影响。方法雄性SD大鼠24只,随机分为3组,8只/组,分别为对照组、肥厚组、实验组。采用腹腔注射NE(1.5 mg/kg,2次/d,28 d)的方法建立心肌肥厚模型,自第15天起实验组腹腔注射SB204741(5-HT2B受体阻断剂;2 mg/kg,2次/d),连续注射14 d。对照组腹腔注射相同体积的生理盐水(2次/d,28 d)。检测各组左心室重量与体重之比(LVW/BW)、心肌组织中5-HT的含量及5-HT2B受体的表达情况。结果在NE诱导心肌肥厚过程中,应用SB204741干预可显著减轻心肌肥厚的程度,降低心肌组织中5-HT的含量,并抑制5-HT2B受体表达的上调。结论应用5-HT2B受体阻断剂可减轻NE诱导心肌肥厚的程度,降低心肌组织中5-HT的含量,并抑制5-HT2B受体表达的上调。     

Serotonin receptors in platelets of bipolar and schizoaffective patients: effect of lithium treatment

Rationale Abnormalities of serotonin (5HT) function have been implicated in mood disorders, and lithium treatment may produce its beneficial effects by modifying serotonergic mechanisms. It has also been observed that 5HT_2A receptors are upregulated both in the postmortem brain and platelets of patients with depression and suicidal behavior. However, the role of 5HT_2A receptors in bipolar disorders and in the mechanism of action of lithium is unclear.Objective The major objective of this study was to examine if abnormalities of 5HT_2A receptors are associated with bipolar or schizoaffective disorders and if treatment with lithium would cause changes in the 5HT_2A receptors.Methods 5HT_2A receptors were studied in the platelets obtained from drug-free normal control subjects and patients with bipolar (n=41) or schizoaffective (n=20) disorders during a drug-free washout period and after treatment (4.0±0.44 weeks) with lithium (n=16). The B_max and K_D of 5HT_2A receptors were quantitated by binding techniques using [¹²⁵I]lysergic acid diethylamide (LSD) as a ligand.Results We observed that the 5HT_2A receptor B_max was increased in platelets obtained from drug-free bipolar or schizoaffective patients as compared with normal control subjects. The 5HT_2A receptor density was even more increased in bipolar or schizoaffective suicidal patients, and the 5HT_2A receptor B_max in the non-suicidal bipolar or schizoaffective subgroup also was significantly higher than in normal control subjects. Treatment with lithium caused a significant increase in the B_max of platelet 5HT_2A receptors in bipolar or schizoaffective patients.Conclusions Our studies indicate that increased 5HT_2A receptors may be associated with the pathophysiology of bipolar illness and that treatment with lithium further increases the density of 5HT_2A receptors. Whether this increase in 5HT_2A receptors caused by lithium is associated with its therapeutic mechanism of action is unclear. It is also not clear whether the increase in 5HT_2A receptors in bipolar or schizoaffective patients, or in suicidal bipolar or schizoaffective patients, is a trait or state marker.     

Anti‐Alzheimer's multitarget‐directed ligands with serotonin 5‐HT6 antagonist,butyrylcholinesterase inhibitory,and antioxidant activity

Serotonin 5‐HT₆ receptors, butyrylcholinesterase (BuChE) and oxidative stress are related to the pathophysiology of Alzheimer's disease. Inhibition of BuChE provides symptomatic treatment of the disease and the same effect was demonstrated for 5‐HT ₆ antagonists in clinical trials. Oxidative stress is regarded as a major and primary factor contributing to the development of Alzheimer's disease; therefore, antioxidant agents may provide a disease‐modifying effect. Combining BuChE inhibition, 5‐HT ₆ antagonism, and antioxidant properties may result in multitarget‐directed ligands providing cognition‐enhancing properties with neuroprotective activity. On the basis of the screening of the library of 5‐HT ₆ antagonists against BuChE, we selected two compounds and designed their structural modifications that could lead to improved BuChE inhibitory activity. We synthesized two series of compounds and tested their affinity and functional activity at 5‐HT ₆ receptors, BuChE inhibitory activity and antioxidant properties. Compound 12 with K _i and K _b values against 5‐HT ₆ receptors of 41.8 and 74 nM, respectively, an IC ₅₀ value of 5 µM against BuChE and antioxidant properties exceeding the activity of ascorbic acid is a promising lead structure for further development of anti‐Alzheimer's agents.     

Synthesis,docking studies,and pharmacological evaluation of 5HT2C ligands containing the N′‐cyanoisonicotinamidine or N′‐cyanopicolinamidine nucleus

N′‐Cyanoisonicotinamidine and N′‐cyanopicolinamidine derivatives, linked to an arylpiperazine moiety, were prepared and their affinities to the 5‐HT_1A, 5‐HT_2A, and 5‐HT_2C receptors were evaluated. Several of the newly synthesized compounds, tested by binding studies, showed nanomolar affinity at the 5‐HT_1A and 5‐HT_2C receptors and moderate or no affinity for other relevant receptors (D₁, D₂, α₁, and α₂). Compound 8e (K_i = 21.4 nM) was the most affine for the 5‐HT_2C receptor, showing, at the same time, a high selectivity with respect to the other receptors analyzed. Compounds 4a and 4c , instead, showed an interesting mixed 5‐HT_1A/5‐HT_2C activity with K_i values of 21.3/11.5 and 23.2/6.48 nM, respectively. The compounds with better affinity and selectivity binding profiles toward 5‐HT_2C ( 4a , 4c , 8b , and 8e ) were selected for further in vivo assays to determine their functional activity. Finally, to rationalize the obtained results, molecular docking studies were performed. The results of the pharmacological studies showed that compounds 4a , 8b , and 8e exerted antidepressant‐like effects and 4a and 8e revealed also significant anxiolytic properties. Among the developed derivatives, the most promising compound seems to be 4a , which displayed antipsychotic‐, antidepressant‐ and anxiolytic‐like properties. No side effects, like catalepsy, motor‐impairment or ethanol‐potentiating effects, were observed after the injection of the tested compounds.     

In vitro functional evaluation of isolaureline,dicentrine and glaucine enantiomers at 5‐HT2 and α1 receptors

Compounds with activity at serotonin (5‐hydroxytryptamine) 5‐HT₂ and α₁ adrenergic receptors have potential for the treatment of central nervous system disorders, drug addiction or overdose. Isolaureline, dicentrine and glaucine enantiomers were synthesized, and their in vitro functional activities at human 5‐HT₂ and adrenergic α₁ receptor subtypes were evaluated. The enantiomers of isolaureline and dicentrine acted as antagonists at 5‐HT₂ and α₁ receptors with (R)‐isolaureline showing the greatest potency (pK_b = 8.14 at the 5‐HT_2C receptor). Both (R)‐ and (S)‐glaucine also antagonized α₁ receptors, but they behaved very differently to the other compounds at 5‐HT₂ receptors: (S)‐glaucine acted as a partial agonist at all three 5‐HT₂ receptor subtypes, whereas (R)‐glaucine appeared to act as a positive allosteric modulator at the 5‐HT_2A receptor.