Hyperforin Potentiates Antidepressant-Like Activity of Lanicemine in Mice

N-methyl-D-aspartate receptor (NMDAR) modulators induce rapid and sustained antidepressant like-activity in rodents through a molecular mechanism of action that involves the activation of Ca²⁺ dependent signaling pathways. Moreover, ketamine, a global NMDAR antagonist is a potent, novel, and atypical drug that has been successfully used to treat major depressive disorder (MDD). However, because ketamine evokes unwanted side effects, alternative strategies have been developed for the treatment of depression. The objective of the present study was to determine the antidepressant effects of either a single dose of hyperforin or lanicemine vs. their combined effects in mice. Hyperforin modulates intracellular Ca²⁺ levels by activating Ca²⁺-conducting non-selective canonical transient receptor potential 6 channel (TRPC6) channels. Lanicemine, on the other hand, blocks NMDARs and regulates Ca²⁺ dependent processes. To evaluate the antidepressant-like activity of hyperforin and lanicemine, a set of in vivo (behavioral) and in vitro methods (western blotting, Ca²⁺ imaging studies, electrophysiological, and radioligand binding assays) was employed. Combined administration of hyperforin and lanicemine evoked long-lasting antidepressant-like effects in both naïve and chronic corticosterone-treated mice while also enhancing the expression of the synapsin I, GluA1 subunit, and brain derived neurotrophic factor (BDNF) proteins in the frontal cortex. In Ca²⁺ imaging studies, lanicemine enhanced Ca²⁺ influx induced by hyperforin. Moreover, compound such as MK-2206 (Akt kinase inhibitor) inhibited the antidepressant-like activity of hyperforin in the tail suspension test (TST). Hyperforin reversed disturbances induced by MK-801 in the novel object recognition (NOR) test and had no effects on NMDA currents and binding to NMDAR. Our results suggest that co-administration of hyperforin and lanicemine induces long-lasting antidepressant effects in mice and that both substances may have different molecular targets.

Chronic antidepressant-like effect of EMD386088, a partial 5-HT6 receptor agonist, in olfactory bulbectomy model may be connected with BDNF and/or CREB signalling pathway

BACKGROUND

The removal of the olfactory bulbs has been attributed to behavioral changes and neuroplasticity manifesting themselves among others like increases in brain neurotrophin expression and neurogenesis. Earlier data presented that EMD386088, a 5-HT6 receptor partial agonist, exerts antidepressant-like properties after chronic administration in olfactory bulbectomy (OB) model as was it compared with amitriptyline (AMI). The aim of this study was to compare acute and chronic biochemical effects of EMD386088, administered in its antidepressant active (2.5mg/kg) and non-active (1.25mg/kg) doses, found in the open field test in OB rats, with those of AMI (10mg/kg). The levels of 5-HT6 receptor protein and selected neurotrophins in prefrontal cortex (PFC) and hippocampus (Hp) of rats have been examined.

METHODS

5-HT6 receptor protein and selected neurotrophins: brain-derived neurotrophic factor (BDNF), cAMP-response element binding protein (CREB), the product of the immediate early gene c-fos (cFos) protein levels were assessed using a Western blot analysis in PFC and Hp of bulbectomized rats after acute or chronic (14-day) EMD386088 or AMI intraperitoneal (ip) treatment.

RESULTS

The acute treatment with EMD386088 caused significant increases in CREB and BDNF protein levels in PFC, and an increase in BDNF in Hp of OB rats, while AMI injection decreased CREB and did not change BDNF levels. After the chronic administration of EMD386088, the increasing levels of BDNF and CREB were still observed in PFC and Hp.

CONCLUSIONS

The antidepressant-like effect of EMD386088 may be associated with the neuroplasticity activation in PFC and Hp in rats.

Optimization and preclinical evaluation of novel histamine H3receptor ligands: Acetyl and propionyl phenoxyalkyl piperazine derivatives

As a continuation of our search for novel histamine H₃ receptor ligands, a series of new acetyl and propionyl phenoxyalkylamine derivatives (2-25) was synthesized. Compounds with three to four carbon atoms alkyl chain spacer, composed of six various 4N-substituted piperazine moieties were evaluated for their binding properties at human histamine H₃ receptors (hH₃R). In vitro test results proved the 4-pyridylpiperazine moiety as crucial element for high hH₃R affinity (hH₃R K_i = 5.2-115 nM). Moreover introduction of carbonyl group containing residues in the lipophilic part of molecules instead of branched alkyl substituents resulted in increased affinity in correlation to previously described series, whereas propionyl derivatives showed slightly higher affinities than those of acetyl (16 and 22vs.4 and 10; hH₃R K_i = 5.2 and 15.4 nM vs. 10.2 and 115 nM, respectively). These findings were confirmed by molecular modelling studies, demonstrating multiple ligand-receptor interactions. Furthermore, pharmacological in vivo test results of compound 4 clearly indicate that it may affect the amount of calories consumed, thus act as an anorectic compound. Likewise, its protective action against hyperglycemia and the development of overweight has been shown. In order to estimate drug-likeness of compound 4, in silico and experimental evaluation of metabolic stability in human liver microsomes was performed.

4-tert-Pentylphenoxyalkyl derivatives - Histamine H3 receptor ligands and monoamine oxidase B inhibitors

The synthesis and biological activity of 4-tert-pentylphenoxypropyl derivatives are described in this manuscript. All compounds (except one) showed human histamine H₃ receptor affinity with K_i values below 760 nM. The inhibitory activity toward human monoamine oxidase B (hMAO B) was evaluated using a fluorometric Amplex-Red assay, and most of the compounds were effective in the submicromolar range. Among them, 1-(3-(4-tert-pPentylphenoxy)propyl)pyrrolidine (5) exhibited hMAO B inhibitory activity with an IC₅₀ value of 4.5 nM. In addition, hMAO B inhibition by 5 was shown to be non-competitive and reversible. Further, recently described potent histamine H₃ receptor ligands - 4-tert-pentylphenoxyalkyl derivatives (with a 4-8 carbon spacer) - were evaluated for hMAO B inhibitory activity, and some of them displayed activity in the submicromolar range. Selected compounds were also tested for human MAO A (hMAO A) inhibitory potencies and exhibited no activity. Moreover, molecular modeling studies were carried out for tested compounds to explain their molecular mechanism of hMAO B inhibition and the selectivity of compounds for hMAO B over hMAO A.

HBK-17, a 5-HT1A Receptor Ligand With Anxiolytic-Like Activity, Preferentially Activates ß-Arrestin Signaling

Numerous studies have proven that both stimulation and blockade of 5-HT_1A and the blockade of 5-HT₇ receptors might cause the anxiolytic-like effects. Biased agonists selectively activate specific signaling pathways. Therefore, they might offer novel treatment strategies. In this study, we investigated the anxiolytic-like activity, as well as the possible mechanism of action of 1-[(2,5-dimethylphenoxy)propyl]-4-(2-methoxyphenyl)piperazine hydrochloride (HBK-17). In our previous experiments, HBK-17 showed high affinity for 5-HT_1A and 5-HT₇ receptors and antidepressant-like properties. We performed the four plate test and the elevated plus maze test to determine anxiolytic-like activity. Toward a better understanding of the pharmacological properties of HBK-17 we used various functional assays to determine its intrinsic activity at 5-HT_1A, 5-HT_2A, 5-HT₇, and D₂ receptors and UHPLC-MS/MS method to evaluate its pharmacokinetic profile. We observed the anxiolytic-like activity of HBK-17 in both behavioral tests and the effect was reversed by the pretreatment with WAY-100635, which proves that 5-HT_1A receptor activation was essential for the anxiolytic-like effect. Moreover, the compound moderately antagonized D₂, weakly 5-HT₇ and very weakly 5-HT_2A receptors. We demonstrated that HBK-17 preferentially activated ß-arrestin signaling after binding to the 5-HT_1A receptor. HBK-17 was rapidly absorbed after intraperitoneal administration and had a half-life of about 150 min. HBK-17 slightly penetrated the peripheral compartment and showed bioavailability of approximately 45%. The unique pharmacological profile of HBK-17 encourages further experiments to understand its mechanism of action fully.

Novel Multitarget-Directed Ligands Aiming at Symptoms and Causes of Alzheimer's Disease

Alzheimer's disease (AD) is a major public health problem, which is due to its increasing prevalence and lack of effective therapy or diagnostics. The complexity of the AD pathomechanism requires complex treatment, e.g. multifunctional ligands targeting both the causes and symptoms of the disease. Here, we present new multitarget-directed ligands combining pharmacophore fragments that provide a blockade of serotonin 5-HT₆ receptors, acetyl/butyrylcholinesterase inhibition, and amyloid β antiaggregation activity. Compound 12 has displayed balanced activity as an antagonist of 5-HT₆ receptors ( K_i = 18 nM) and noncompetitive inhibitor of cholinesterases (IC_{50 hAChE} = 14 nM, IC_{50 eqBuChE} = 22 nM). In further in vitro studies, compound 12 has shown amyloid β antiaggregation activity (IC₅₀ = 1.27 μM) and ability to permeate through the blood-brain barrier. The presented findings may provide an excellent starting point for further studies and facilitate efforts to develop new effective anti-AD therapy.

Anticonvulsant evaluation of novel non-imidazole histamine H3R antagonists in different convulsion models in rats

Novel non-imidazole histamine H3 receptor (H3R) antagonists (2-8) were developed and assessed for in-vitro antagonist binding affinities at the human histamine H1-H4R. These novel H3R antagonists (2-8) were examined in-vivo for anticonvulsant effects in three different convulsion models in male adult rats. Compound 6 significantly and dose-dependently exhibited decreased duration of tonic hind limb extension (THLE) in the maximal electroshock (MES)- and fully protected animals against pentylenetetrazole (PTZ)-induced convulsion, following acute systemic administration (5, 10, and 20 mg/kg, i.p.). Contrary, all compounds 2-8 showed moderate protection in the strychnine (STR)-induced convulsion model following acute pretreatment (10 mg/kg, i.p.). Moreover, the acute systemic administration of H3R antagonist 6 (10 mg/kg, i.p.) significantly prolonged latency time for MES convulsions. Furthermore, the anticonvulsant effect observed with compound 6 in MES-model was entirely abrogated when rats were co-injected with the brain penetrant H1R antagonist pyrilamine (PYR) but not the brain penetrant H2R antagonist zolantidine (ZOL). However, PYR and ZOL failed to abolish the full protection provided by the H3R antagonist 6 in PTZ- and STR-models. No mutagenic or antiproliferative effects or potential metabolic interactions were shown for compound 6 when assessing its antiproliferative activities and metabolic profiling applying in-vitro methods. These findings demonstrate the potential of non-imidazole H3R antagonists as novel antiepileptic drugs (AEDs) either for single use or in addition to currently available epilepsy medications.

Design, synthesis and cardiovascular evaluation of some aminoisopropanoloxy derivatives of xanthone

A series of aminoisopropanoloxy derivatives of xanthone has been synthesized and their pharmacological properties regarding the cardiovascular system has been evaluated. Radioligand binding and functional studies in isolated organs revealed that title compounds present high affinity and antagonistic potency for α₁-(compound 2 and 8), β-(compounds 1, 3, 4, 7), α₁/β-(compounds 5 and 6) adrenoceptors. Furthermore, compound 7, the structural analogue of verapamil, possesses calcium entry blocking activity. The title compounds showed hypotensive and antiarrhythmic properties due to their adrenoceptor blocking effect. Moreover, they did not affect QRS and QT intervals, and they did not have proarrhythmic potential at tested doses. In addition they exerted anti-aggregation effect. The results of this study suggest that new compounds with multidirectional activity in cardiovascular system might be found in the group of xanthone derivatives.

Synthesis and biological evaluation of N-arylpiperazine derivatives of 4,4-dimethylisoquinoline-1,3(2H,4H)-dione as potential antiplatelet agents

Despite the substantial clinical success of aspirin and clopidogrel in secondary prevention of ischemic stroke, up to 40% of patients remain resistant to the available antiplatelet treatment. Therefore, there is an urgent clinical need to develop novel antiplatelet agents with a novel mechanism of action. Recent studies revealed that potent alpha 2B-adrenergic receptor (alpha 2B-ARs) antagonists could constitute alternative antiplatelet therapy. We have synthesized a series of N-arylpiperazine derivatives of 4,4-dimethylisoquinoline-1,3(2H,4H)-dione as potential alpha 2B receptor antagonists. The most potent compound 3, effectively inhibited the platelet-aggregation induced both by collagen and ADP/adrenaline with IC₅₀ of 26.9 μM and 20.5 μM respectively. Our study confirmed that the alpha 2B-AR antagonists remain an interesting target for the development of novel antiplatelet agents with an alternative mechanism of action.

Antiallodynic and antihyperalgesic activity of new 3,3-diphenyl-propionamides with anticonvulsant activity in models of pain in mice

Anticonvulsant drugs are used to treat a wide range of non-epileptic conditions, including chronic pain. The aim of the present experiments was to examine analgesic activity of three new 3,3-diphenyl-propionamides, which had previously demonstrated anticonvulsant activity in the MES (maximal electroshock seizure), scPTZ (subcutaneous pentylenetetrazole) and/or 6Hz (psychomotor seizure) tests in mice. Antinociceptive activity was examined in mouse models of acute pain (the hot plate test) and tonic pain (the formalin test) in mice. Antiallodynic and antihyperalgesic activity was estimated in the oxaliplatin-induced neuropathic pain model of chemotherapy-induced peripheral neuropathy and in the streptozotocin-induced model of painful diabetic neuropathy in mice. Considering the drug safety evaluation, the influence on locomotor activity was checked. Moreover, using in vitro methods, selected compound was tested for potential hepatotoxicity on human hepatocellular carcinoma cell line and for metabolic stability. To determine the plausible mechanism of anticonvulsant and antinociceptive action, in vitro binding and functional assays were carried out. Among tested molecules two of them JOA 122 (3p) and JOA 123 (3q) revealed significant antinociceptive activity in the model of tonic pain - the formalin test and neuropathic pain models - the oxaliplatin and streptozotocin-induced peripheral neuropathy. In the binding studies JOA 122 (3p) revealed the high affinity to voltage-gated sodium channels (Na_v1.2), as well as for 5-HT_1A receptors. Metabolism studies in mouse liver microsomes showed a low metabolic stability of this compound.

5-HT1A and 5-HT2A receptors affinity, docking studies and pharmacological evaluation of a series of 8-acetyl-7-hydroxy-4-methylcoumarin derivatives

In this work we describe the synthesis, docking studies and biological evaluation of a focused library of novel arylpiperazinyl derivatives of 8-acetyl-7-hydroxy-4-methylcoumarin. The new compounds were screened for their 5-HT_1A and 5-HT_2A receptor affinity. Among the evaluated compounds, six displayed high affinities to 5-HT_1A receptors (4a-0.9 nM, 6a-0.5 nM, 10a-0.6 nM, 3b-0.9 nM, 6b-1.5 nM, 10b-1 nM). Compound 6a and 10a bearing a bromo- or methoxy- substituent in ortho position of the piperazine phenyl ring, were identified as potent antagonists of the 5-HT_1A receptors. In the tail suspension test, mice injected with 6a showed a dose-dependent increase in depressive-like behavior that was related to a decrease in locomotor activity. Compound 10a did not decrease or prolong immobility time nor did it affect home cage activity. Molecular docking studies using 5-HT_1A and 5-HT_2A homology models revealed structural basis of the high affinity of ortho-substituted derivatives and subtle changes in amino acid interactions patterns depending on the length of the alkyl linker.

HBK-14 and HBK-15, triple 5-HT1A, 5-HT7 and 5-HT3 antagonists with potent antidepressant- and anxiolytic-like properties, increase seizure threshold in various seizure tests in mice

Most antidepressants lower seizure threshold, which might be due to the modulation of serotonergic neurotransmission. Here, we investigated the effects of two 5-HT_1A, 5-HT₇ and 5-HT₃ antagonists, i.e., 1-(2-(2-(2,6-dimethylphenoxy)ethoxy)ethyl)-4-(2-methoxyphenyl)piperazine hydrochloride (HBK-14) and 1-{2-[2-(2-chloro-6-methylphenoxy)ethoxy]ethyl}-4-(2-methoxyphenyl)piperazine hydrochloride (HBK-15), with antidepressant- and anxiolytic-like properties, on seizure thresholds in three acute seizure tests, i.e., the intravenous pentylenetetrazole, maximal electroshock seizure threshold (MEST), and 6-Hz corneal stimulation test in mice. We also evaluated their affinity for voltage-gated sodium channels. Our results indicate that HBK-14 increased seizure thresholds in three seizure tests in mice, while HBK-15 was active in the MEST and 6-Hz tests. None of the compounds affected neuromuscular strength or motor coordination at active doses. We showed that both compounds had high affinity for voltage-dependent sodium channels, which combined with the influence on 5-HT_1A, 5-HT₇ and 5-HT₃ receptors, might underlie their anticonvulsant effects. Since most antidepressants lower the seizure threshold, the fact that both compounds with potent antidepressant-like activity, increased or had no influence on seizure threshold is worth investigating.

Novel 3-(1,2,3,6-Tetrahydropyridin-4-yl)-1H-indole-Based Multifunctional Ligands with Antipsychotic-Like, Mood-Modulating, and Procognitive Activity

The most troublesome aspects of behavioral and psychological symptoms of dementia (BPSD) are nowadays addressed by antidepressant, anxiolytic, and antipsychotic drugs, often administered off-label. Considering their modest effectiveness in dementia patients, the increased risk of adverse events and cognitive decline, there is an unmet need for well-tolerated and effective therapy of BPSD. We designed and synthesized multifunctional ligands characterized in vitro as high-affinity partial agonists of D₂R, antagonists of 5-HT₆R, and blockers of SERT. Moreover, the molecules activated 5-HT_1AR and blocked 5-HT₇R while having no relevant affinity for off-target M₁R and hERG channel. Compound 16 (N-{2-[4-(5-chloro-1H-indol-3-yl)-1,2,3,6-tetrahydropyridin-1-yl]ethyl}-3-methylbenzene-1-sulfonamide) exhibited a broad antipsychotic-, antidepressant-, and anxiolytic-like activity, not eliciting motor impairments in mice. Most importantly, 16 showed memory-enhancing properties and it ameliorated memory deficits induced by scopolamine. The molecule outperformed most important comparators in selected tests, indicating its potential in the treatment of both cognitive and noncognitive (behavioral and psychological) symptoms of dementia.

Development of selective agents targeting serotonin 5HT1A receptors with subnanomolar activities based on a coumarin core

A series of 18 new 5-[3-(4-aryl-1-piperazinyl)propoxy]coumarin derivatives from the corresponding bromoalkyl derivatives have been designed and synthesized by us using a microwave-assisted protocol. Radioligand binding assays of this series of compounds as well as a previously synthesized series of 17 structurally-similar compounds showed that six systems have very high affinities to the 5-HT1A receptor (0.3-1.0 nM) and good selectivity against the 5-HT2A receptor. Molecular docking, structural studies and structure-activity relationship studies were used to gain more insight into the atomistic details of ligand binding and rationalize the obtained results.

Biphenyloxy-alkyl-piperidine and azepane derivatives as histamine H3 receptor ligands

Novel biphenyloxy-alkyl derivatives of piperidine and azepane were synthesized and evaluated for their binding properties at the human histamine H₃ receptor. Two series of compounds were obtained with a meta- and a para-biphenyl moiety. The alkyl chain spacer contained five and six carbon atoms. The highest affinity among all compounds was shown by 1-(6-(3-phenylphenoxy)hexyl)azepane (13) with a K_i value of 18nM. Two para-biphenyl derivatives, 1-(5-(4-phenylphenoxy)pentyl)piperidine (14; K_i=25nM) and 1-(5-(4-phenylphenoxy)pentyl)azepane (16; K_i=34nM), classified as antagonists in a cAMP accumulation assay (IC₅₀=4 and 9nM, respectively), were studied in detail. Compounds 14 and 16 blocked RAMH-induced dipsogenia in rats (ED₅₀ of 2.72mg/kg and 1.75mg/kg respectively), and showed high selectivity (hH₄R vs hH₃R>600-fold) and low toxicity (hERG inhibition: IC₅₀>1.70µM; hepatotoxicity IC₅₀>12.5µM; non-mutagenic up to 10µM). Furthermore, the metabolic stability was evaluated in vitro on human liver microsomes (HLMs) and/or rat liver microsomes (RLMs). Metabolites produced were analyzed and tentatively identified by UPLC-MS techniques. The results demonstrated easy hydroxylation of the biphenyl ring.

3-Aminomethyl Derivatives of 2-Phenylimidazo[1,2-a]-pyridine as Positive Allosteric Modulators of GABAA Receptor with Potential Antipsychotic Activity

Schizophrenia is a mental illness characterized by behavioral changes as well as anatomical and neurochemical abnormalities. There has been remarkable progress in the drug discovery for schizophrenia; however, antipsychotics that act through molecular targets, other than monoaminergic receptors, have not been developed. One of the hypotheses of schizophrenia states that GABAergic dysfunction might be implemented in the pathophysiology of this disease. Our recent findings and previous clinical observations have suggested that modulation of GABAergic system through α₁-GABA_A receptors would represent an original approach for the treatment of schizophrenia. This study presents the synthesis and biological evaluation of a series of fluorinated 3-aminomethyl derivatives of 2-phenylimidazo[1,2-a]-pyridine as potential antipsychotic agents. Compound 7 has a high affinity for GABA_A receptor (K_i = 27.2 nM), high in vitro metabolic stability, and antipsychotic-like activity in amphetamine-induced hyperlocomotion test in rats (MED = 10 mg/kg). Compound 7 represents a promising point of entry in the course of development of antipsychotic agents with a nondopaminergic mechanism of action.

Synthesis of a new series of aryl/heteroarylpiperazinyl derivatives of 8-acetyl-7-hydroxy-4-methylcoumarin with low nanomolar 5-HT1A affinities

We synthesized a series of aryl/heteroarylpiperazinyl derivatives of 8-acetyl-7-hydroxy-4-methylcoumarin and evaluated their antidepressant-like activity. We used a fast, microwave-assisted synthesis protocol and ¹H, ¹³C NMR and HRMS spectrometry to confirm the structure of all compounds. We also used radioligand binding assays to determine the affinities towards 5-HT_1A and 5-HT_2A receptors and performed molecular docking studies to rationalize obtained results. Among the evaluated compounds seven displayed high affinity to the 5-HT_1A (3a-1.3 nM, 5a-1.6 nM, 10a-1.6 nM, 11a-1.0 nM, 3b-1.0 nM, 5b-0.8 nM and 11b-1.5 nM) as well as significant 5-HT_1A antagonist profiles. The equilibrium dissociation constant values of tested compounds shown differential intrinsic activity (3a-190 nM, 3b-28 nM, 5a-48 nM, 5b-23 nM, 10b-180 nM, 11a-99 nM, 11b-38 nM) of antagonist mode. Molecular docking studies using a homology model of 5-HT_1A revealed that ligand 5b is stabilized mainly by hydrogen bonds to Ser190.

Molecular mechanism of action and safety of 5-(3-chlorophenyl)-4-hexyl-2,4-dihydro-3H-1,2,4-triazole-3-thione - a novel anticonvulsant drug candidate

Previously, it was found that 5-(3-chlorophenyl)-4-hexyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (TP-315) effectively protects mice from maximal electroshock-induced seizures. The aim of this study was to determine possible interactions between TP-315 and different molecular targets, i.e. GABA_A receptors, voltage-gated sodium channels, and human neuronal α7 and α4β2 nicotinic acetylcholine receptors. The influence of TP-315 on the viability of human hepatic HepG2 cells was also established using PrestoBlue and ToxiLight assays. It was found that the anticonvulsant activity of TP-315 results (at least partially) from its influence on voltage-gated sodium channels (VGSCs). Moreover, the title compound slightly affected the viability of human hepatic cells.

NEW SPIROHYDANTOIN DERIVATIVES - SYNTHESIS, PHARMACOLOGICAL EVALUATION, AND MOLECULAR MODELING STUDY

A series of new arylpiperazinylpropyl derivatives of 8/6-phenyl-1,3-diazaspiro[4.5]decan-2,4-dione and spiro[imidazolidine-4,1'-indene/naphthalene]-2,5-dione was synthesized and their affinity was evaluated toward serotonin 5-HTIA, 5-HT2A, 5-HT7 receptors, dopaminergic D2, D3 receptors, adrenergic ox, receptors, and serotonin transporter (SERT). The highest affinity for serotonin 5-HT1A/2A/7 receptors was found for compounds containing a tetralin or indane moiety in the imide part. Among these, two compounds (19, 20) were selected for further pharmacological in vivo studies. A binding mode of representative molecule 19, which behaved as a 5-HT1A agonist and weak 5-HT7 antagonist in the site of 5-HT 1A/7, was also analyzed in computational stud- ies. Moreover, two highly selective (9 and HI) 5-HT₂A receptor antagonists were obtained.

Synthesis and activity of newly designed aroxyalkyl or aroxyethoxyethyl derivatives of piperazine on the cardiovascular and the central nervous systems

In the search for new hypotensive agents some new aroxyalkyl or aroxyethoxyethyl derivatives of piperazine have been synthesized and evaluated for their pharmacological properties. Pharmacological tests included receptor binding assays toward adrenergic receptors α₁, α₂ and β₁, additionally 5-HT_1A, functional bioassay and in vivo evaluation of hypotensive activity as well as antidepressant-like potential. All the tested compounds exhibited α₁-antagonistic properties, three of them possessed also hypotensive activity in rats. The most promising compound 3 1-[4-(2,6-dimethylphenoxy)butyl]-4-(2-methoxyphenyl)piperazine hydrochloride was a selective α₁ receptor antagonist (K_i=23.5±1.3, α₁/α₂=15.77, pK_B=8.538±0.109). It was active in all tested doses in vivo (1, 0.5, and 0.1mg/kg) and it reduced blood pressure by 10-13% at the dose of 1mg/kg (rats, i.v.). Compound 5 1-[2-(2,3-dimethylphenoxy)ethoxyethyl]-4-(2-methoxyphenyl)piperazine dihydrochloride exhibited the lowest dose for antidepressant-like activity 5mg/kgb.w. (mice, i.p.) without influence on spontaneous activity (mice, i.p.).

Arylsulfonamide derivatives of (aryloxy)ethyl pyrrolidines and piperidines as α1-adrenergic receptor antagonist with uro-selective activity

A series of arylsulfonamide derivatives of (aryloxy)ethyl pyrrolidines and piperidines was synthesized to develop new α₁-adrenoceptor antagonists with uroselective profile. Biological evaluation for α₁- and α₂-adrenorecepor showed that tested compounds 13-37 displayed high-to-moderate affinity for the α₁-adrenoceptor (K_i=34-348nM) and moderate selectivity over α₂-receptor subtype. Compounds with highest affinity and selectivity for α₁-adrenoceptor were evaluated in vitro for their intrinsic activity toward α_1A- and α_1B-adrenoceptor subtypes. All compounds behaved as antagonists at both α₁-adrenoceptor subtypes, displaying 2- to 6-fold functional preference to α_1A-subtype. Among them, N-{1-[2-(2-methoxyphenoxy)ethyl]piperidin-4-yl}isoquinoline-4-sulfonamide (25) and 3-chloro-2-fluoro-N-{[1-(2-(2-isopropoxyphenoxy)ethyl)piperidin-4-yl]methyl}benzene sulfonamide (34) displayed the highest preference to α_1A-adrenoceptor. Finally, compounds 25 and 34 (2-5mg/kg, iv), in contrast to tamsulosin (1-2mg/kg, iv), did not significantly decrease systolic and diastolic blood pressure in normotensive anesthetized rats to determine their influence on blood pressure.

Structure-5-HT/D2 Receptor Affinity Relationship in a New Group of 1-Arylpiperazynylalkyl Derivatives of 8-Dialkylamino-3,7-dimethyl-1H-purine-2,6(3H,7H)-dione

In our previous papers, we have reported that some 8-amino-1,3-dimethyl-1H-purine-2,6(3H,7H)-dione derivatives possessed high affinity and displayed agonistic, partial agonistic, or antagonistic activity for serotonin 5-HT_1A and dopamine D₂ receptors. In order to examine further the influence of the substituent in the position 8 of the purine moiety and the influence of the xanthine core on the affinity for serotonin 5-HT_1A , 5-HT_2A , 5-HT₆ , 5-HT₇ , and dopamine D₂ receptors, two series of 1-arylpiperazynylalkyl derivatives of 8-amino-3,7-dimethyl-1H-purine-2,6(3H,7H)-dione were synthesized. All the final compounds were investigated in in vitro competition binding experiments for the serotonin 5-HT_1A , 5-HT_2A , 5-HT₆ , 5-HT₇ , and dopamine D₂ receptors. The structure-affinity relationships for this group of compounds were discussed. For selected compounds, the functional assays for the 5-HT_1A and D₂ receptors were carried out. The results of the assays indicated that these groups of derivatives possessed antagonistic activity for 5-HT_1A receptors and agonistic, partial agonistic, or antagonistic activity for D₂ receptors. In total, 26 new compounds were synthesized, 20 of which were tested in in vitro binding experiments and 5 were tested in in vitro functional assays.