选择性5-HT1A受体拮抗剂WAY-100635抑制帕金森病模型大鼠腹内侧前额叶皮质的神经活动

目的腹内侧前额叶皮质在随意运动的起始和控制、情感以及认知中具有重要作用。然而,黑质-纹状体通路变性后腹内侧前额叶皮质的神经活动和5-HT_(1A)受体的作用仍不清楚。本研究观察了6-羟基多巴胺(6- hydroxydopamine,6-OHDA)损毁黑质致密部(substantia nigra pars compacta,SNc)后大鼠腹内侧前额叶皮质神经活动的变化和体循环给予选择性5-HT_(1A)受体拮抗剂WAY-100635后神经元活动的改变。方法采用在体玻璃微电极细胞外记录方法,记录正常大鼠和SNc单侧损毁大鼠的腹内侧前额叶皮质神经元的活动。结果6-OHDA损毁SNc大鼠的腹内侧前额叶皮质神经元放电频率显著增加,放电形式没有明显改变。体循环给予WAY-100635 (0.1 mg/kg,i.v.)不改变正常大鼠腹内侧前额叶皮质神经元的平均放电频率和放电形式,而显著降低了SNc损毁大鼠前额叶皮质神经元的平均放电频率。结论黑质-纹状体通路的变性可导致腹内侧前额叶皮质神经活动增强,5-HT_(1A)受体拮抗剂WAY-100635可以抑制这种活动增强,提示可能存在腹内侧前额叶皮质5-HT_(1A)受体功能失调。     

Two selective 5-HT1A receptor antagonists, WAY-100 635 and NDL-249, stimulate locomotion in rats acclimatised to their environment and alter their behaviour: a behavioural analysis

The aim was to study firstly, the motor effects of a new 5-HT_1A antagonist, NDL-249 [(R)-3-(N-cyclopentyl-N-propylamino)-8-fluoro-3,4-dihydro-2H-1-benzopyran-5-carboxamide hydrochloride] and of the reference 5-HT_1A antagonist WAY-100 635 [N-(2-(1-(4-(2-methoxyphenyl)piperazinyl))ethyl)-N-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride], in comparison to the 5-HT_1A agonist (±)-8-OH-DPAT [(8-hydroxy-2-(di-N-propylamino) tetralin, hereafter 8-OH-DPAT], in rats acclimatised to the automated activity cages; secondly, to study whether the behavioural effects of NDL-249 and 8-OH-DPAT are sensitive to the 5-HT depleting effects of p-chlorophenylalanine (PCPA); thirdly, to characterise the nature of the antagonist-induced activation seen in the automatic activity cages with the aid of a behavioural observation analysis; fourthly, to examine the interaction between the 5-HT_1Areceptors mediating the behavioural effects and dopamine (DA) receptors. NDL-249 was found to bind in vitro to rat hippocampal 5-HT_1A receptors with high affinity and selectivity. In second messenger studies, it was devoid of agonist-like effects. In the locomotor activity studies, each antagonist significantly increased the incidence of horizontal activity, peripheral activity and rearing. 8-OH-DPAT, while significantly increasing peripheral and horizontal activities, decreased the incidence of rearing. PCPA blocked the motor effects of NDL-249 but did not affect those of 8-OH-DPAT. Observational analyses indicated that NDL-249 induced significant increases at one or more doses in sniffing, rearing and locomotion together with a significant reduction in stillness. WAY-100 635 significantly increased the incidence of rearing, intense grooming and vacuous chewing. The significant increases in sniffing, grooming and intense grooming and the significant decrease in stillness induced by the DA D₁ agonist, SK&F 38393 [(±)-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol hydrochloride], were not altered by concomitant pre-treatment with NDL-249. Pre-treatment of rats with either the DA D₁ antagonist SCH-23390 (2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepin-7-ol) or the DA D₂ antagonist, raclopride, blocked the reduced stillness and increased sniffing and rearing induced by NDL-249. In conclusion, 5-HT_1A antagonists including the new selective antagonist, NDL-249, induce mild behavioural activation in rats, which is mediated probably indirectly via DA systems. Received: 3 April 1997/Final version: 23 February 1998     

Evidence for the involvement of the 5-HT1A receptor in CCK induced satiety in rats

The present study was designed to examine possible interactions between exogenous CCK and the 5-HT_1A receptor subtype mediated serotonergic effects on feeding in rats. The somatodendritic 5-HT_1A receptor agonist 8-OH-DPAT (0.32 mg/kg sc) evoked feeding in freely feeding rats. This effect was attenuated by treatment with CCK-8 (1, 5 and 25 g/kg ip). In food deprived rats, CCK-8 (40 g/kg ip) significantly reduced the size of a test meal. Treatment with the 5-HT_1A receptor antagonist WAY-100135 (10 mg/kg ip) antagonized this anorectic effect of CCK-8. WAY-100135 on its own did not affect food intake. These results suggest the involvement of the 5-HT_1A receptor subtype in mediating 5-HT-CCK interactions in the control of food intake in rats.     

Pindolol binding to 5-HT1A receptors in the human brain confirmed with positron emission tomography

The augmentation effect of (–)pindolol as used in combination with SSRI to treat major depression has been ascribed to blocking of dorsal raphe nucleus cell body 5-HT autoreceptors. In this study, the radioligand [carbonyl-¹¹C]WAY-100635 and positron emission tomography were used to establish whether pindolol at a clinical dose level (10 mg s.o.d.) occupies 5-HT_1A receptors in the human brain in vivo. Three healthy males were recruited and each subject was used as his own control. The 5-HT_1A receptor occupancy was calculated for the frontal and temporal cortex and the raphe nuclei, using and a ratio analysis with the cerebellar cortex as the reference region. Maximal pindolol plasma concentration was reached within 3 h after drug administration. Two hours after pindolol administration, the regional 5-HT_1A receptor occupancy was within the range 7–21% in the three subjects. The study confirms that the 5-HT_1A-receptor may be a clinically significant target for pindolol. Received: 8 March 1999 / Final version: 15 March 1999     

5-HT1A受体拮抗剂WAY-100635的合成

2-氨基吡啶和2-氯乙酰氯经酰胺化、与N'-(邻甲氧基苯基)哌嗪缩合、氢化铝锂还原得4-(邻甲氧基苯基)-1-[2-[(2-吡啶基)氨基]乙基]哌嗪,再与环己甲酰氯缩合得到5-HT1A受体拮抗剂WAY-100635,总收率35%.     

Inhibitory effects of tandospirone, a 5-HT1A agonist, on medial vestibular nucleus neurons responding to lateral roll tilt stimulation in rats

An electrophysiological study was performed using chloral hydrate-anesthetized rats to determine whether tandospirone, a 5-HT_1A agonist, affects neuronal activities of the medial vestibular nucleus (MVN), since serotonergic innervation and 5-HT_1A receptors are present in this nucleus. Tandospirone applied microiontophoretically at a current of 20–60 nA caused an inhibition of tilt-induced firing of -type neurons, which showed increased and decreased firing with lateral tilt ipsilateral and contralateral to the recording site, respectively, along with that of β-type neurons which exhibited the reverse responses to ipsilateral and contralateral tilt stimulation. The inhibition was antagonized during simultaneous, iontophoretic application of WAY-100635 (20–60 nA), a 5-HT_1A receptor antagonist, although WAY-100635 alone rarely affected spontaneous or tilt-induced firing in either type of neurons. These results suggest that tandospirone acts on a 5-HT_1A receptor to inhibit transmission of otolith information to - and β-type MVN neurons.     

Effects of acute and chronic buspirone on impulsive choice and efflux of 5-HT and dopamine in hippocampus, nucleus accumbens and prefrontal cortex

Rationale Reduced central serotonin (5-HT) activity has been associated with impulsive choice behaviour, but there is no consensus about the precise nature of these effects. Behavioural and neurochemical effects of 5-HT_1A agonists such as buspirone depend critically on the dose and the duration of treatment. We thus undertook a parametric study of the effects of acute and chronic buspirone on the performance on a test of delayed gratification, as well as on the efflux of serotonin and dopamine (DA) in cortical and subcortical regions in rats.Objectives Three experiments examined (i) the effects of acute buspirone on impulsive choice and how such effects were modified by prior chronic exposure to buspirone; (ii) the effects of chronic buspirone on impulsive choice; (iii) the effects on impulsive choice of a selective 5-HT_1A antagonist, WAY-100635 tested alone and in combination with buspirone; (iv) the effects of chronic and acute buspirone on 5-HT and DA efflux in anaesthetised rats.Methods In experiment 1, rats previously trained on the delayed gratification task were tested with acute buspirone (0.5, 1 and 2 mg/kg). The same rats were then treated with chronic buspirone (1 mg/kg/day) over the next 65 days, and the effects of acute buspirone (1 mg/kg) re-determined at 20, 45 and 65 days of chronic treatment. In experiment 2, two groups of rats trained on the delayed gratification task were treated either with saline or buspirone (1 mg/kg/day) continually for 65 days before being tested with acute buspirone (1 mg/kg), WAY-100635 (0.08 mg/kg), or a combination of the two drugs. In experiment 3, rats received the same regimen of buspirone dosing as in experiment 2, before receiving in-vivo microdialysis for 5-HT and DA in the ventral hippocampus, nucleus accumbens and medial prefrontal cortex.Results Acute buspirone dose dependently increased the choice for the small, immediate reinforcer (impulsive choice) but the effects of 1 mg/kg were reversed on chronic administration of buspirone. This increased choice of the large, delayed reinforcer, which was not accompanied by any changes in baseline (non-drugged) performance, was blocked by the 5-HT_1A receptor antagonist WAY-100635. The chronic buspirone regimen did not alter buspirone-evoked reductions in 5-HT efflux in hippocampus but did lead to a differential effect of acute buspirone in medial prefrontal cortex, with the chronic buspirone and saline groups exhibiting decreases and increases in efflux, respectively. There were no systematic changes in DA efflux under any condition.Conclusions These findings show that the effects of acute buspirone on impulsive choice are reversed following chronic treatment and are mediated by 5-HT_1A receptors, and suggest, in addition, that the behavioural effects may involve changes in 5-HT functioning in medial prefrontal cortex.     

Two <Emphasis Type="Italic">C</Emphasis>-Methyl Derivatives of [<Superscript>11</Superscript>C]WAY-100635 – Effects of an Amido <Emphasis Type="Bold">α</Emphasis>-Methyl Group on Metabolism and Brain 5-HT<Subscript>1A</Subscript> Receptor Radioligand Behavior in Monkey*

PURPOSE: [carbonyl-11C]N-(2-(1-(4-(2-methoxyphenyl)-piperazinyl)ethyl)-N-pyridinyl)cyclohexanecarboxamide ([carbonyl-11C]WAY-100635) is an effective radioligand for imaging brain 5-HT1A receptors with positron emission tomography (PET). However, this radioligand has some drawbacks for deriving relative regional receptor densities, including rapid metabolism, which acts against accurate definition of an arterial input function for compartmental modeling, and very low nonspecific binding in brain, which detracts from the accuracy of modeling by a simplified reference tissue (cerebellum) approach. Here, in a search for a radioligand that overcomes these limitations, we investigated the effects of introducing a single methyl group at either of the carbon atoms alpha to the amide bond in [11C]WAY-100635. PROCEDURES: Ligands with a methyl group on the alpha carbon of the cyclohexyl group (SWAY) or the alpha carbon of the C2H4 linker ((R,S)-JWAY) were synthesized and tested for binding affinity and intrinsic activity at 5-HT1A receptors. SWAY was labeled with carbon-11 (t1/2 = 20.4 minutes; beta+ = 99.8%) in its O-methyl group and (R,S)-JWAY in its carbonyl group. Each radioligand was evaluated by PET experiments in cynomolgus monkey. RESULTS: SWAY and (R,S)-JWAY were found to be high-affinity antagonists at 5-HT1A receptors. After injection of [11C]SWAY into monkey, radioactivity uptake in brain reached a maximum of 3% at 4.5 minutes and decreased to 0.7% at 72 minutes. However, over the time span of the experiment, radioactivity concentrations in 5-HT1A receptor-rich brain regions were only fractionally higher than in cerebellum. Radioactivity represented by parent radioligand in plasma was 39% at 45 minutes. After injection of [11C](R,S)-JWAY alone, radioactivity uptake in brain reached a maximum of 4.8% at 2.5 minutes and decreased to 1.2% at 90 minutes. At this time, radioactivity concentration in 5-HT1A receptor-rich brain regions was markedly greater than in cerebellum. In another PET experiment, the monkey was predosed with WAY-100635 before [11C](R,S)-JWAY injection. At 90 minutes after injection, the ratio of radioactivity in 5-HT1A receptor-rich regions to that in cerebellum was reduced to near unity. Radioactivity represented by parent radioligand in plasma was 12% at 45 minutes. CONCLUSIONS: [11C](R,S)-JWAY, but not [11C]SWAY, gives a sizeable 5-HT1A receptor-selective PET signal in monkey. The presence of a C-methyl group adjacent to the amide bond in SWAY or (R,S)-JWAY fails to counter metabolism.     

Evidence that 5-hydroxytryptamine7 receptors play a role in the mediation of afferent transmission within the nucleus tractus solitarius in anaesthetized rats

Background and purpose:

Central 5-hydroxytryptamine (5-HT)-containing pathways utilizing 5-HT₇ receptors are known to be critical for the mediation of cardiovascular reflexes. The nucleus tractus solitarius (NTS) is a site involved in the integration of cardiovascular afferent information. The present experiments examined the involvement of the 5-HT₇ receptor in the processing of cardiovascular reflexes in the NTS.

Experimental approach:

In anaesthetized rats extracellular recordings were made from 104 NTS neurones that were excited by electrical stimulation of the vagus nerve and/or activation of cardiopulmonary afferents. Drugs were applied ionophoretically in the vicinity of these neurones.

Key results:

The non-selective 5-HT₇ receptor agonist 5-carboxamidotryptamine maleate (5-CT) applied to 78 neurones increased the firing rate in 18 by 59% and decreased it in 38 neurones by 47%. Similarly, the 5-HT_1A agonist 8-OH-DPAT applied to 20 neurones had an excitatory (8), inhibitory (7) or no effect (5) on the 20 neurones tested. In the presence of the 5-HT₇ antagonist SB 258719 the 5-CT excitation was attenuated. Furthermore, the excitatory response of NTS neurones evoked by electrical stimulation of the vagus nerve or activation of cardiopulmonary afferents with intra atrial phenylbiguanide was attenuated by SB 258719. The inhibitory action of 5-CT was unaffected by SB 258719 and the 5-HT_1A antagonist WAY-100635. WAY-100635 failed to have any effect on 5-CT and vagal afferent-evoked excitations.

Conclusions and implications:

Vagal afferent-evoked excitation of NTS neurones can be blocked by SB 258719, a selective 5-HT₇ antagonist. This observation further supports the involvement of 5-HT neurotransmission in NTS afferent processing.     

WAY-100635 has high selectivity for serotonin 5-HT(1A) versus dopamine D(4) receptors

The serotonin 5-HT(1A) receptor antagonist WAY-100635 was recently reported to have potent agonist properties at dopamine D(4) receptors (Chemel et al., 2006, Psychopharmacology 188, 244-251.). Herein WAY-100635 (pK(i) at human (h) serotonin 5-HT(1A) receptors=9.51; pK(i) at dopamine hD(4.4) receptors=7.42) stimulated [(35)S]GTPgammaS incorporation in membranes of Chinese Hamster Ovary cells expressing dopamine hD(4.4) receptors with only moderate potency and modest efficacy (pEC(50)=6.63; E(max)=19% of dopamine). Moreover, in antagonism experiments, WAY-100635 had a much lower potency at dopamine hD(4.4) receptors (pK(B)=7.09), than at serotonin h5-HT(1A) receptors (pK(B)=9.47). These data demonstrate that WAY-100635 has high selectivity for serotonin h5-HT(1A)versus dopamine hD(4.4) receptors.