Synthesis and structure-activity relationship of 2-(aminoalkyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives: a novel series of 5-HT(2A/2C) receptor antagonists. Part 2.

Following the programme started at Janssen Research Foundation searching for 5-HT(2A/2C) antagonists, we now report on the synthesis of a series of substituted 2-(Dimethylaminomethyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives. The 5-HT(2A), 5-HT(2C) and H(1) receptor affinities as well as the mCPP antagonistic activity of the compounds synthesised is described.     

Pyrrolo(iso)quinoline derivatives as 5-HT(2C) receptor agonists

A series of 1-(1-pyrrolo(iso)quinolinyl)-2-propylamines was synthesised and evaluated as 5-HT(2C) receptor agonists for the treatment of obesity. The general methods of synthesis of the precursor indoles are described. The functional efficacy and radioligand binding data for the compounds at 5-HT(2) receptor subtypes are reported. The analogue which showed the highest 5-HT(2C) binding affinity (27, 1.6nM) was found to be successful in reducing food intake in rats.     

2-(Dimethylaminomethyl)-tetrahydroisoxazolopyridobenzazepine derivatives. Synthesis of a new 5-HT2C antagonist with potential anxiolytic properties

Following the program started at Johnson & Johnson Pharmaceutical Research & Development searching for 5-HT_2A/2C antagonists, we now report on the synthesis of 2-(dimethylaminomethyl)-2,3,3a,8-tetrahydroisoxazolo[3,2-a]pyrido[3,4-c]-[2]benzazepine and 2-(dimethylaminomethyl)-2,3,3a,8-tetrahydroisoxazolo[3,2-a]pyrido[3,2-c]-[2]benzazepine. A new method for the synthesis of pyridobenzazepines is described as well. The affinities for several receptors as well as the mCPP antagonistic activity of the compounds synthesised are described.     

4-(2-Aminoethoxy)-N-(phenylsulfonyl)indoles as novel 5-HT6 receptor ligands

The preparation of a novel class of 4-(2-aminoethoxy)-N-(phenylsulfonyl)indoles which exhibit high affinity towards the 5-HT6 receptor is reported here. Among these compounds, 4-(2-methylaminoethoxy)-N-(phenylsulfonyl)indole 5g showed superior affinity (Ki = 1 nM) towards the 5-HT6 receptor as well as excellent selectivity (> 2000-fold) against the closely related subtype 5-HT7 receptor.     

Proterguride, a highly potent dopamine receptor agonist promising for transdermal administration in Parkinson's disease: interactions with alpha(1)-, 5-HT(2)- and H(1)-receptors

Dopamine receptor agonists play an important role in the treatment of Parkinson's disease and hyperprolactinemic conditions. Proterguride (n-propyldihydrolisuride) was already reported to be a highly potent dopamine receptor agonist, thus its action at different non-dopaminergic monoamine receptors, alpha(1A/1B/1D), 5-HT(2A/2B)- and histamine H(1), was investigated using different functional in vitro assays. The drug behaved as an antagonist at alpha(1)-adrenoceptors without the ability to discriminate between the subtypes (pA(2) values: alpha(1A) 7.31; alpha(1B) 7.37; alpha(1D) 7.35) and showed antagonistic properties at the histamine H(1) receptor. In contrast, at serotonergic receptors (5-HT(2A), 5-HT(2B)) proterguride acted as a partial agonist. The drug stimulated 5-HT(2A) receptors of rat tail artery in lower concentrations than 5-HT itself but failed to evoke comparable efficacy (proterguride: pEC(50) 8.34, E(max) 53% related to the maximum response to 5-HT; 5-HT: pEC(50) 7.03). Agonism at 5-HT(2B) receptors is presently considered to be involved in drug-induced valvular heart disease. Activation of 5-HT(2B) receptors in porcine pulmonary arteries by proterguride (pEC(50) 7.13, E(max) 49%; E(max) (5-HT) 69%), however, occurred at concentrations much higher than plasma concentrations achieving dopaminergic efficacy in humans. The results are discussed focussing on the relevance of action at 5-HT(2B) receptors as well as their significance for a transdermal administration of proterguride. Since it is well accepted that pulsatile dopaminergic stimulation is associated with treatment-related motor complications in the dopaminergic therapy of Parkinson's disease, the transdermal route of administration is of great clinical interest due to the possibility to achieve constant plasma concentrations.     

Bivalent ligand approach on 4-[2-(3-methoxyphenyl)ethyl]-1-(2-methoxyphenyl)piperazine: synthesis and binding affinities for 5-HT(7) and 5-HT(1A) receptors

We here report on the synthesis and binding properties at 5-HT(7) and 5-HT(1A) receptors of ligands 3-12, that were designed according to the 'bivalent ligand' approach. Two moieties of the 5-HT(7)/5-HT(1A) ligand 4-[2-(3-methoxyphenyl)ethyl]-1-(2-methoxyphenyl)piperazine (1) were linked through their 3-methoxy substituent by polymethylene chains of variable length, with the aim to increase the affinity for 5-HT(7) receptor and the selectivity over 5-HT(1A) receptors. In the best cases, the dimers showed affinities for 5-HT(7) receptors as high as the monomer with no improvement in selectivity. Some dimers displayed 5-HT(1A) receptor affinities slightly higher than monomer 1.     

2-(Dimethylaminomethyl)-tetrahydroisoxazolopyridobenzazepine derivatives. Synthesis of a new 5-HT(2C) antagonist with potential anxiolytic properties

Following the program started at Johnson & Johnson Pharmaceutical Research & Development searching for 5-HT_2A/2C antagonists, we now report on the synthesis of 2-(dimethylaminomethyl)-2,3,3a,8-tetrahydroisoxazolo[3,2-a]pyrido[3,4-c]-[2]benzazepine and 2-(dimethylaminomethyl)-2,3,3a,8-tetrahydroisoxazolo[3,2-a]pyrido[3,2-c]-[2]benzazepine. A new method for the synthesis of pyridobenzazepines is described as well. The affinities for several receptors as well as the mCPP antagonistic activity of the compounds synthesised are described.     

Indoline derivatives as 5-HT(2C) receptor agonists

A series of 1-(1-indolinyl)-2-propylamines was synthesised and evaluated as 5-HT(2C) receptor agonists for the treatment of obesity. The general methods of synthesis of the precursor indoles are described. The functional efficacy and radioligand binding data for all of the compounds at 5-HT(2) receptor subtypes are reported. A number of compounds were found to reduce food intake in rats after oral administration.     

Synthesis and structure-activity relationship of 2-(aminoalkyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives: a novel series of 5-HT(2A/2C) receptor antagonists. Part 1.

The synthesis of a series of novel 2-(aminoalkyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives as well as their 5-HT(2A/2C) and H(1) receptor binding affinities are described. The in vivo activity as potential anxiolytics of the synthesised compounds was measured in a mCPP challenge test. One of the compounds, 2a, proved to be a potent 5-HT(2A/2C) receptor antagonist showing as well oral activity and therefore could be considered as a potential anxiolytic/antidepressant agent.     

Synthesis and structure-activity relationships of a series of substituted 2-(1H-furo[2,3-g]indazol-1-yl)ethylamine derivatives as 5-HT2C receptor agonists

A series of novel indazole derivatives were synthesized, and their structure-activity relationships examined in order to identify potent and selective 5-HT2C receptor agonists. Among these compounds, (S)-2-(7-ethyl-1H-furo[2,3-g]indazol-1-yl)-1-methylethylamine (YM348) had a good in vitro profile, that is, high agonistic activity to the human 5-HT2C receptor subtype (EC50 = 1.0 nM) and high selectivity over 5-HT2A receptors. This compound was also effective in a rat penile erection model when administered p.o.     

Long-term estrogen therapy and 5-HT(2A) receptor binding in postmenopausal women; a single photon emission tomography (SPET) study

Variation in estrogen level is reported by some to affect brain maturation and memory. The neurobiological basis for this may include modulation of the serotonergic system. No neuroimaging studies have directly examined the effect of extended estrogen therapy (ET), on the 5-HT(2A) receptor in human brain. We investigated the effect of long-term ET on cortical 5-HT(2A) receptor availability in postmenopausal women. In a cross-sectional study, we compared cortical 5-HT(2A) receptor availability in 17 postmenopausal ERT-naive women and 17 long-term oophorectomised estrogen-users, age- and IQ-matched using single photon emission tomography and the selective 5-HT(2A) receptor ligand (123)I-5-I-R91150. Also, we used the Revised Wechsler Memory Scale to relate memory function to 5-HT(2A) receptor availability. Never-users had significantly higher 5-HT(2A) receptor availability than estrogen-users in hippocampus (1.17 vs. 1.11, respectively, p=0.02), although this did not remain significant after correction for multiple comparisons. Hippocampal 5-HT(2A) receptor availability correlated negatively with verbal and general memory and delayed recall (r=-0.45, p=0.01; r=-0.40, p=0.02; r=-0.36, p=0.04). Right superior temporal 5-HT(2A) receptor availability correlated negatively with verbal memory (r=-0.36, p=0.04). In estrogen-users, receptor availability correlated negatively with verbal and general memory (r=-0.70, p=0.002; r=-0.69, p=0.002); and in never-users, receptor availability negatively correlated with attention and concentration (r=-0.54, p=0.02). Long-term ET may be associated with lower 5-HT(2A) receptor availability in hippocampus. This may reflect increased activity within the serotonergic pathway leading to down-regulation of post-synaptic receptor. Also, increased availability of the 5-HT(2A) receptor in hippocampus is associated with poorer memory function.     

Discriminative stimulus properties of the serotonergic agent 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)

Using a two-lever drug discrimination procedure, six rats were trained to discriminate 0.5 mg/kg of racemic 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) from saline. Once trained, the animals demonstrated a dose-related decrease in discriminative performance upon administration of lower doses of DOI (ED50 = 0.16 mg/kg). DOI-stimulus generalization occurred with the putative 5-HT2 agonist DOM (ED50 = 0.49 mg/kg), but not with the 5-HT1A agonist 8-OH DPAT, or the 5-HT1B agonist TFMPP. Furthermore, the DOI stimulus could be antagonized by pretreatment of the animals with the 5-HT2 antagonist ketanserin. The present results, coupled with the prior demonstration that DOI possesses a significant affinity and selectivity for 5-HT2 binding sites, suggest that the discriminative stimulus effects of DOI may be 5-HT2-mediated.     

Interactions of N-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-2-aryl-2-yl-acetamides and 1-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-3-aryl-2-yl-ureas with dopamine D2 and 5-hydroxytryptamine 5HT(1A) receptors

It is suggested that the ratio of dopamine D(2) to 5-hydroxytryptamine 5-HT(1A) activity is an important parameter that determines the efficiency of antipsychotic drugs. Here we present the synthesis of N-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-2-aryl-2-yl-acetamides and 1-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-3-aryl-2-yl-ureas and their structure-activity relationship studies on dopamine D(2) and 5-hydrohytryptamine 5-HT(1A) receptors. It was shown that ligand selectivity and affinity strongly depends on their topology and the presence of a pyridyl group in the head of molecules. Molecular modeling studies using homology modeling and docking simulation revealed a rational explanation for the ligand behavior. The observed binding modes and receptor-ligand interactions provided us with a clue for optimizing the optimal selectivity towards 5-HT(1A) receptors.     

Synthesis and in vivo evaluation of [O-methyl-11C] N-[3,5-dichloro-2-(methoxy)phenyl]-4-(methoxy)-3-(1-piperazinyl)benzenesulfonamide as an imaging probe for 5-HT6 receptors

The serotonin receptor 6 (5-HT(6)) is implicated in the pathophysiology of cognitive diseases, schizophrenia, anxiety and obesity and in vivo studies of this receptor would be of value for studying the pathophysiology of these disorders. Therefore, N-[3,5-dichloro-2-(methoxy)phenyl]-4-(methoxy)-3-(1-piperazinyl)benzenesulfonamide (SB399885), a selective and high affinity (pK(i)=9.11) 5-HT(6) antagonist, has been radiolabeled with carbon-11 by O-methylation of the corresponding desmethyl analogue with [(11)C]MeOTf in order to determine the suitability of [(11)C]SB399885 to quantify 5-HT(6)R in living brain using PET. Desmethyl-SB399885 was prepared, starting from 1-(2-methoxyphenyl) piperazine hydrochloride, in excellent yield. The yield obtained for radiolabeling of [(11)C]SB399885 was 30±5% (EOS) and the total synthesis time was 30min at EOB. PET studies with [(11)C]SB399885 in baboon showed fast uptake followed by rapid clearance in the brain. Highest uptake of radioactivity of [(11)C]SB399885 in baboon brain were found in temporal cortex, parahippocampal gyrus, pareital cortex, amygdala, and hippocampus. Poor brain entry and inconsistent brain uptake of [(11)C]SB399885 compared to known 5-HT(6)R distribution limits its usefulness for the in vivo quantification of 5-HT(6)R with PET.     

5-HT(2A) receptors: location and functional analysis in intestines of wild-type and 5-HT(2A) knockout mice

The distribution and function of the 5-hydroxytryptamine (5-HT(2A)) receptor were investigated in the intestines of wild-type (5-HT(2A) +/+) and knockout (5-HT(2A) -/-) mice. In 5-HT(2A) +/+ mice, rats, and guinea pigs, 5-HT(2A) receptor immunoreactivity was found on circular and longitudinal smooth muscle cells, neurons, enterocytes, and Paneth cells. Muscular 5-HT(2A) receptors were concentrated in caveolae; neuronal 5-HT(2A) receptors were found intracellularly and on the plasma membranes of nerve cell bodies and axons. Neuronal 5-HT(2A) immunoreactivity was detected as early as E14 in ganglia, intravillus nerves, and the deep muscle plexus. The 5-HT(2A) -/- colon did not express 5-HT(2A) receptors and did not contract in response to exogenous 5-HT. 5-HT(2A) -/- enterocytes were smaller, Paneth cells fewer, and muscle layers thinner (and showed degeneration) compared with those of 5-HT(2A) +/+ littermates. The 5-HT(2A) receptor may thus be required for the maintenance and/or development of enteric neuroeffectors and other enteric functions, although gastrointestinal and colonic transit times in 5-HT(2A) -/- and +/+ mice did not differ significantly.     

Involvement of 5-HT(2) receptor in imipramine-induced hyperglycemia in mice.

Effects of imipramine on plasma glucose levels were investigated in mice. Imipramine i. p. induced dose-dependent hyperglycemia, which was enhanced by pretreatment with 5-HT (1/2/5/7) receptor antagonist methysergide and 5-HT (2A/2B/2C) receptor antagonist LY 53857. 5-HT (2C/2B) receptor antagonist SB 206553 also augmented imipramine-induced hyperglycemia although 5-HT (1A) and 5-HT (1B) receptor antagonist (-)-propranolol,5-HT (2A) receptor antagonist ketanserin and 5-HT (3/4) receptor antagonist tropisetron each had no effect. Imipramine i. p.-induced hyperglycemia was antagonized by the 5-HT (2C/2B) receptor agonist 1-(3-chlorophenyl)piperazine (mCPP), while the 5-HT (2B) receptor agonist BW 723C86 had no effect. Intracerebroventricular injection of imipramine also elevated plasma glucose levels, which is enhanced by SB 206553. Hyperglycemia elicited by central injection of imipramine was abolished by adrenalectomy. These results suggest that imipramine-induced hyperglycemia in mice is related to its inhibition of the central 5-HT (2C) receptor. Moreover, our results indicate that adrenaline release is related to imipramine-induced hyperglycemia.     

Synthesis of 7-amino-3a,4-dihydro-3H-[1]benzopyrano[4,3-c]isoxazole derivatives displaying combined alpha2-adrenoceptor antagonistic and 5-HT reuptake inhibiting activities

Following a program searching for dual 5-HT reuptake inhibitors and alpha(2)-adrenoceptor antagonists started at Johnson & Johnson Pharmaceutical Research & Development, we now report on the synthesis of a series of 7-amino-3a,4-dihydro-3H-[1]benzopyrano[4,3-c]isoxazole derivatives, some of which proved to be the most potent alpha(2)-adrenoceptor blockers within this chemical class of tricyclic isoxazolines, while keeping potent 5-HT reuptake inhibiting activity.     

2-(Anilino)imidazolines and 2-(benzyl)imidazoline derivatives as h5-HT1D serotonin receptor ligands

2-(Anilino)imidazolines were identified as novel human 5-HT(1D) receptor ligands, but offered no particular advantage over previously reported 2-(benzyl)imidazolines. Pharmacokinetic and functional data were obtained for selected 2-(benzyl)imidazoline derivatives.     

Structural determinants for high 5-HT(2A) receptor affinity of spiro[9,10-dihydroanthracene]-9,3(')-pyrrolidine (SpAMDA)

The synthesis and 5-HT(2A) receptor affinities of ring altered derivatives of spiro[9,10-dihydroanthracene]-9,3(')-pyrrolidine (4), a structurally unique tetracyclic 5-HT(2A) receptor antagonist, are described. The characteristics of the parent compound prove to be necessary for optimal 5-HT(2A) receptor affinity. However, expansion of the size of the pyrrolidine and central rings produce compounds with reasonably high 5-HT(2A) receptor affinities. In addition, the parent compound is shown to have high 5-HT(2) receptor selectivity.     

Serotonin 5-HT(2A) receptor activation induces 2-arachidonoylglycerol release through a phospholipase c-dependent mechanism

To date, several studies have demonstrated that phospholipase C-coupled receptors stimulate the production of endocannabinoids, particularly 2-arachidonoylglycerol. There is now evidence that endocannabinoids are involved in phospholipase C-coupled serotonin 5-HT(2A) receptor-mediated behavioral effects in both rats and mice. The main objective of this study was to determine whether activation of the 5-HT(2A) receptor leads to the production and release of the endocannabinoid 2-arachidonoylglycerol. NIH3T3 cells stably expressing the rat 5-HT(2A) receptor were first incubated with [(3)H]-arachidonic acid for 24 h. Following stimulation with 10 mum serotonin, lipids were extracted from the assay medium, separated by thin layer chromatography, and analyzed by liquid scintillation counting. Our results indicate that 5-HT(2A) receptor activation stimulates the formation and release of 2-arachidonoylglycerol. The 5-HT(2A) receptor-dependent release of 2-arachidonoylglycerol was partially dependent on phosphatidylinositol-specific phospholipase C activation. Diacylglycerol produced downstream of 5-HT(2A) receptor-mediated phospholipase D or phosphatidylcholine-specific phospholipase C activation did not appear to contribute to 2-arachidonoylglycerol formation in NIH3T3-5HT(2A) cells. In conclusion, our results support a functional model where neuromodulatory neurotransmitters such as serotonin may act as regulators of endocannabinoid tone at excitatory synapses through the activation of phospholipase C-coupled G-protein coupled receptors.