Synthesis and development of new 2-substituted 1-[3-(4-arylpiperazin-1-yl)propyl]-pyrrolidin-2-one derivatives with antiarrhythmic, hypotensive, and alpha-adrenolytic activity

A series of new 1-[3-(4-arylpiperazinyl-1-yl)-2-(N-alkylcarbamoyloxy)propyl]-pyrrolidin-2-one derivatives (4a-12a) were synthesised and tested for their electrocardiographic, antiarrhythmic and antihypertensive activity, as well as for the alpha1- and alpha2-adrenoceptor binding affinities. Of the newly synthesised derivatives, 1-{2-(N-2-methylethylcarbamoiloxy)-3-[4-(2-methoxyphenyl)piperazin-1-yl)]propyl}pyrrolidin-2-one dihydrochloride (10a) was the most active in prophylactic antiarrhythmic tests, its ED50 value equalling 2.7 mg kg(-1), and the therapeutic index being 75.2; moreover, compound 10a was also found to possess hypotensive activity. A preliminary molecular modelling study suggested that the selected alpha1-AR antagonist distances and angles between pharmacophoric features, estimated for the tested compounds, were in good agreement with the parameters evaluated for ligands.     

Search for New Antiarrhythmic and Hypotensive Compounds. Synthesis,Antiarrhythmic, Antihypertensive,and α-Adrenoceptor Blocking Activity of Novel 1-[(2-Hydroxy-3-amino)]-propylpyrrolidin-2-one Derivatives

A series of the derivatives of 1-[2-hydroxy-3-(4-phenyl-1-piperazinyl)propyl]-pyrrolidin-2-one ( MG-1 ) was synthesized and tested for electrocardiographic, antiarrhythmic, and antihypertensive activity as well as for α₁- and α₂- adrenoceptors binding affinities. Some of the compounds of this series slightly decreased the heart rate, prolonged P-Q, Q-T intervals and QRS complex. Only compound 7 (1-[2-hydroxy-3-(4-phenyl-1-piperazinyl)propyl]-pyrrolidine) possesses potent antiarrhythmic and a slight hypotensive properties, and affinity for α₁- and α₂- adrenoceptor. The results suggest that the antiarrhythmic and hypotensive effect of compound 7 and MG-1 is related to their adrenolytic properties, and that those properties depend on the presence of a phenylpiperazine moiety.     

Antidepressant-like activity of the phenylpiperazine pyrrolidin-2-one derivatives in mice

The present study was designed to investigate the central nervous system activity of 23 novel phenylpiperazine pyrrolidin-2-one derivatives. These compounds had marked antiarrhythmic and hypotensive activities and revealed affinity for α1- and α2-adrenoceptors. These effects may be related to their α-adrenolytic properties. We assessed their antidepressant-like effect in the forced swimming test, influence of spontaneous locomotor activities and binding to 5-HT1A and 5-HT2 receptors. Our study demonstrated the strong antidepressant-like activity of compound EP-65 in the forced swimming test. The effect of EP-65 was stronger than results obtained with the classical antidepressants imipramine and mianserin. Other compounds, EP-41, EP-42, EP-44, EP-47, EP-48, EP-49, EP-50, EP-62, EP-66, EP-70, EP-75 and EP-76, showed significantly weaker activities in this test. Compound EP-42 showed the strongest affinity for 5-HT1A (Ki=24.5 nM), and compound EP-50 showed the strongest affinity for the 5-HT2 receptor (Ki=109.1 nM). All tested compounds significantly suppressed the spontaneous locomotor activity of mice. Currently, it is not possible to determine which mechanisms are involved in the witnessed antidepressant-like activity of novel phenylpiperazine pyrrolidin-2-one derivatives.     

Antiarrhythmic and hypotensive activities of 1-[2-hydroxy-3-(4-phenyl-1-piperazinyl)propyl]-pyrrolidin-2-one (MG-1(R,S)) and its enantiomers

The compound MG-1(R,S), (1-[2-hydroxy-3(4-phenyl-1-piperazinyl)propyl]-pyrrolidin-2-one, and its enantiomers were tested for electrocardiographic, antiarrhythmic and hypotensive activities. The racemic mixture (MG-1(R,S)) and its S-enantiomer significantly decreased systolic and diastolic blood pressure and possessed antiarrhythmic activity. The S-enantiomer displayed the greatest effect. The R-enantiomer did not show antiarrhythmic or hypotensive activity. The results suggest that the antiarrhythmic and hypotensive effects of these compounds are related to their adrenolytic properties.     

Synthesis and pharmacological evaluation of pyrrolidin-2-one derivatives as antiarrhythmic,antihypertensive and α-adrenolytic agents

A series of novel arylpiperazines bearing a pyrrolidin-2-one fragment were synthesized and evaluated for their binding affinity for α₁– and α₂ -adrenoceptors (ARs) as well as their antiarrhythmic and antihypertensive activities. The highest affinity for the α₁-AR was displayed by 1-{3-[4-(2-chloro-phenyl)-piperazin-1-yl]-propyl}-pyrrolidin-2-one 7, which binds with a pK_i = 7.13. The highest affinity for the α₂-AR was shown by 1-{3-[4-(4-chloro-phenyl)-piperazin-1-yl]-propyl}-pyrrolidin-2-one 18, which binds with a pK_i = 7.29. Among the compounds tested, 1-{3-[4-(2-ethoxy-phenyl)-piperazin-1-yl]-propyl}-pyrrolidin-2-one 13 had the highest prophylactic antiarrhythmic activity in epinephrine-induced arrhythmia in anesthetized rats. Its ED₅₀ value was 1.0 mg/kg intravenously (iv). The compounds with a hydroxy group in the 4-position of the phenyl ring or two substituents such as fluorine atoms in the 2 and 4 positions of the phenyl ring significantly decreased systolic and diastolic pressure in normotensive anesthetized rats at a dose of 2.5 mg/ kg iv, and their hypotensive effects lasted for longer than an hour.     

Antiarrhythmic and antioxidant activity of novel pyrrolidin-2-one derivatives with adrenolytic properties

A series of novel pyrrolidin-2-one derivatives (17 compounds) with adrenolytic properties was evaluated for antiarrhythmic, electrocardiographic and antioxidant activity. Some of them displayed antiarrhythmic activity in barium chloride-induced arrhythmia and in the rat coronary artery ligation-reperfusion model, and slightly decreased the heart rate, prolonged P-Q, Q-T intervals and QRS complex. Among them, compound EP-40 (1-[2-hydroxy-3-[4-[(2-hydroxyphenyl)piperazin-1-yl]propyl]pyrrolidin-2-one showed excellent antiarrhythmic activity. This compound had significantly antioxidant effect, too. The present results suggest that the antiarrhythmic effect of compound EP-40 is related to their adrenolytic and antioxidant properties. A biological activity prediction using the PASS software shows that compound EP-35 and EP-40 can be characterized by antiischemic activity; whereas, compound EP-68, EP-70, EP-71 could be good tachycardia agents.     

A Search for New 5-HT1A/5-HT2A Receptor Ligands. In Vitro and in vivo Studies of 1-[ω-(4-Aryl-1-piperazinyl)alkyl]indolin-2(1H)-ones

A series of 1-[ω-(4-aryl-1-piperazinyl)alkyl]indolin-2(1H)-one derivatives 2–14 was synthesized in order to obtain ligands with a dual 5-HT_1A/5-HT_2A activity. The majority of those compounds ( 2–5, 7, 10–13 ) exhibited a high 5-HT_1A (K_i = 2 – 44 nM) and/or 5-HT_2A affinity (K_i = 51 and 39 for 5 and 7 , respectively). Induction of lower lip retraction (LLR) and behavioral syndrome and inhibition of these efects evoked by 8-hydroxy-2-(di-n-propyl-amino)tetralin (8-OH-DPAT) were used for determination the agonistic and antagonistic activity, respectively, at 5-HT_1A receptors. The 5-HT_2A antagonistic activity was assessed by the blocking effect on the head twitches induced by (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in mice. Two of the tested compounds, 1-{3-[4-(3-chlorophenyl)-1-piperazinyl]propyl}-6-fluoroindolin-2(1H)-one ( 5 ) and 1-{3-[4-(2-methoxyphenyl)-1-piperazinyl]propyl}indolin-2(1H)-one ( 7 ), demonstrated a high 5-HT_1A/5-HT_2A affinity and an in vivo antagonistic activity towards both receptor subtypes.     

Selective agonists reveal alpha(1A)- and alpha(1B)-adrenoceptor subtypes in caudal artery of the young rat

Multiple alpha(1)-adrenoceptors were evaluated in caudal artery of the young Wistar rat using selective agonists and antagonists. Arteries were exposed to the selective alpha(1A)-adrenoceptor agonist, A-61603 (N-[5-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl] methanesulfonamide) or to phenylephrine and to prazosin (alpha(1)-adrenoceptor antagonist), or the selective alpha(1A)-adrenoceptor antagonists 5-methylurapidil, RS 100329 (5-methyl-3-[3-[4-[2-(2,2,2,-trifluoroethoxy)phenyl]-1-piperazinyl]propyl]-2,4-(1H)-pyrimidinedione), RS 17053 (N-[2(2-cyclopropylmethoxy) ethyl]-5-chloro-alpha, alpha-dimethyl-1H-indole-3-ethanamide), and the selective alpha(1D)-adrenoceptor antagonist BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5] decane-7,9-dione). Results showed a 100-fold higher potency of A-61603 for the alpha(1)-adrenoceptor present in the artery, compared with phenylephrine. Prazosin displaced both agonists with high affinity, whereas 5-methylurapidil, RS 100329 and RS 17053 displaced A-61603 with high affinity, indicating the presence of alpha(1A)-adrenoceptors. The selective alpha(1A)-adrenoceptor antagonists blocked phenylephrine responses with low affinity, suggesting that phenylephrine activated a second receptor population in caudal artery. BMY 7378 antagonized with low affinity both A-61603 and phenylephrine-induced contractions, indicating absence of alpha(1D)-adrenoceptors in the vessel. The results suggest that functional alpha(1B)-adrenoceptors are present in caudal arteries of the young Wistar rat.     

Synthesis and structure-activity relationships of 4-cycloalkylamino-1, 2, 4-triazolo[4, 3-a]quinoxalin-1- one derivatives as A1 and A3 adenosine receptor antagonists

In a previous paper we reported the synthesis and binding activity of 4-cycloalkylamino-1, 2, 4-triazolo[4, 3-a]quinoxalin-1-one derivatives, differently substituted on the appended 2-phenyl ring, some of which were potent and selective A(1) adenosine receptor (AR) antagonists. In the present paper several 4-cycloalkylamino-2-phenyl-1, 2, 4-triazolo[4, 3-a]quinoxalin-1-one derivatives (1-11), bearing simple substituents on the benzofused moiety, are reported. The binding data of bovine A(1) and A(2A) and human A(3) AR show that we have obtained highly potent A(1) AR antagonists. In particular, the 4-cyclohexylamino derivatives 1-5 show higher A(1) vs A(2A) selectivity than the parent compound A, which lacks substituents on the benzofused moiety. Moreover, compounds 1-11 display, in general, good A(3) AR affinity. Finally, SAR studies provide some new insights about the steric requirements of the A(3) receptor pocket, which accommodates the benzofused moiety of our 4-amino-triazoloquinoxalin-1-one derivatives.     

The Structure—Activity Relationship of a New Anti-Arrhythmic Agent 1-[2-Acetoxy-3-(4-phenyl-1-piperazinyl)propyl]pyrrolidin-2-one

This paper reports the synthesis of the new compound 1-[2-acetoxy-3-(4-phenyl-1-piperazinyl)propyl]pyrrolidin-2-one (Ac-MG-1). Preliminary pharmacological assessment revealed that Ac-MG-1 possesses anti-arrhythmic activity and a local anesthetic effect. The crystal structure of Ac-MG-1 was determined by X-ray diffraction, and conformational analysis was performed both for Ac-MG-1 and for other derivatives of (arylpiperazinyl)propylpyrrolidin-2-one.     

1-cinnamyl-4-(2-methoxyphenyl)piperazines: synthesis, binding properties, and docking to dopamine (D(2)) and serotonin (5-HT(1A)) receptors

Clinical properties of atypical antipsychotics are based on their interaction with D(2) dopamine receptor and serotonin 5-HT(1A) and 5-HT(2A) receptors. As a part of our research program on new antipsychotics, we synthesized various derivatives of 1-cinnamyl-4-(2-methoxyphenyl)piperazines, and evaluated their affinities for D(2), 5-HT(1A), 5-HT(2A), and adrenergic (alpha(1)) receptors using radioligand-binding assays. In addition, we performed docking analysis using models for the D(2) and 5-HT(1A) receptors. All compounds exhibited low to moderate affinity to 5-HT(1A) and 5-HT(2A) receptors, high affinity to the D(2 )receptor and large variability in affinities for the alpha(1) receptor. Docking analysis indicated that the binding to D(2) and 5-HT(1A) receptors is based on (i) interaction between protonated N1 of the piperazine ring and various aspartate residues, (ii) hydrogen bonds between various moieties of the ligand and the residues of threonine, serine, histidine or tryptophane, and (iii) edge-to-face interactions of the aromatic ring of the arylpiperazine moiety with phenylalanine or tyrosine residues. Docking data for the D(2) receptor can account for the binding properties obtained in binding assays, suggesting that the model is reliable and robust. However, docking data for the 5-HT(1A) receptor cannot account for actual binding properties, suggesting that further refinement of the model is required.     

Selective, centrally acting serotonin 5-HT2 antagonists. 1. 2- and 6-substituted 1-phenyl-3-(4-piperidinyl)-1H-indoles.

A series of 1-[2-[4-(1H-indol-3-yl)-1-piperidinyl]ethyl]-2-imidazolidinones has been synthesized. The 1-position of the indole is substituted with phenyl groups and in the 2- or 6-positions are additional substituents. An analogous series with the imidazolidinone ring opened to corresponding urea derivatives was also prepared. High potency and selectivity for 5-HT2 receptors (as compared with D2 and alpha 1 receptor affinities) were obtained with medium-large substituents such as 6-chloro, 6-methyl, and 6-trifluoromethyl or a 2-methyl substituent. Larger 6-substituents such as isopropyl considerably reduced activity, while the smaller 6-fluoro substituent afforded unselective compounds. Selective 5-HT2 antagonists were found by combining 6-substitution with both unsubstituted 1-phenyl and substituted 1-phenyl groups (2-F, 4-F, 4-Cl). However, 3-substitution of the phenyl group markedly reduced 5-HT2 receptor affinity, especially with a 3-trifluoromethyl substituent. Introduction of a 3-(2-propyl) substituent in the imidazolidinone ring reduced binding to alpha 1 adrenoceptors with a factor of 3-8. Practically no influence on 5-HT2 and D2 receptor affinities were found by the presence of this substituent compared to the 3-unsubstituted derivatives. Compounds with potent receptor binding also potently inhibited the quipazine-induced head twitch syndrome in rats. The compounds were equally active after oral and subcutaneous administration and they had a long duration of action (> 24 h). Especially urea derivatives were found to be considerably more potent at 24 h than at 2 h after subcutaneous administration. Some of the compounds potently inhibited isolation-induced aggression in mice, an effect which, however, did not correlate to 5-HT2 receptor-mediated activities. On the basis of these structure-activity studies 1-[2-[4-[6-chloro-1-(4-fluorophenyl)-1H-indol-3-yl]-1- piperidinyl]ethyl]-3-(2-propyl)-2-imidazolidinone (Lu 26-042, compound 4c) was selected for further pharmacological and toxicological investigations.     

Design and synthesis of novel benzopyran-2-one derivatives of expected antimicrobial activity through DNA gyrase-B inhibition

In an attempt to find a new class of antibacterial agents, we have synthesized thirty new coumarin (2H-benzopyran-2-one) analogues. These derivatives include substituted azetidin-2-ones (beta-lactam) 3a-f, pyrrolidin-2-ones 4a-f, 2H-1,3,4-oxadiazoles 5a-f, and thiazolidin-4-ones 6a-f attached to 4-phenyl-2H-benzopyran-2-one through an oxyacetamido or an oxymethyl bridge. The target compounds were synthesized starting from 2-oxo-4-phenyl-2H-benzo[b]pyran-7-yl-oxyacetic acid hydrazides 2a-f. The new compounds were evaluated as DNA gyrase-B inhibitors through molecular modeling and docking techniques using the Molsoft ICM 3.4-8C program. The synthesized compounds were also screened for antibacterial activity against four different species of Gram-positive and Gram-negative bacteria; as well as screening against C. albicans for antifungal activity. The molecular modeling data were in accordance with the antimicrobial screening results.     

Synthesis, nicotinic acetylcholine receptor binding, and antinociceptive properties of 2-exo-2-(2'-substituted 5'-pyridinyl)-7-azabicyclo[2.2.1]heptanes. Epibatidine analogues

A convenient, high-yield synthesis of 7-tert-butoxycarbonyl-7-azabicyclo[2.2.1]hept-2-ene (5), which involved the addition of tributyltin hydride to 7-tert-butoxycarbonyl-2-p-toluenesulfonyl-7-azabicyclo[2.2.1]hept-2-ene (4) followed by elimination of the tributyltin and p-tolylsulfonyl groups using tetrabutylammonium fluoride was developed. The addition of 2-amino-5-iodopyridine to 5 under reductive Heck conditions provided 7-tert-butoxycarbonyl-2-exo-(2'-amino-5'-pyridinyl)-7-azabicyclo[2.2.1]heptane (6). Compound 6 was the key intermediate used to prepare epibatidine analogues where the 2'-chloro group on the pyridine ring was replaced with a fluorine (1b), bromine (1c), iodine (1d), hydroxy (1e), amino (1f), dimethylamino (1g), trifluoromethanesulfonate (1h), and hydrogen (1i) group. (+)- and (-)-Epibatidine and compounds 1b-d and 1i all possess similar binding affinities at the alpha(4)beta(2) nAChR receptors labeled by [(3)H]epibatidine. Compound 1f has affinity similar to nicotine, whereas compounds 1e, 1g, and 1h have much lower affinity. The binding affinity appears to be dependent upon the electronic nature of the substituent. However, other factors are also involved. None of the compounds possesses appreciable affinity for the alpha(7) nAChR labeled by [(125)I]iodo-MLA. With the exception of 1f and 1g, all the epibatidine analogues are full agonists (tail flick test) in producing antinociception after intrathecal injection in mice.     

Structure-cardiovascular activity relationships in a group of new 8-alkylamino-1,3-dimethyl-7-(2-hydroxy-3-aminopropyl)-3,7-dihydro-1H-purine-2,6-diones

On the basis of our earlier studies in a group of 7,8-disubstituted derivatives of 1,3-dimetyl-3,7-dihydropurine-2,6-dione, a series of new 8-alkylamino-1,3-dimethyl-7-(2-hydroxy-3-aminopropyl)-3,7-dihydropurine-2,6-diones (8-15) were synthesized and tested for their electrocardiographic, antiarrhythmic and hypotensive activity and for α(1)- and α(2)-adrenoreceptor affinities. Among the new derivatives, compounds with the 7-[2-hydroxy-3-(4-phenylpiperazine)-propyl] substituent (9-11) displayed prophylactic antiarrhythmic activity in epinephrine-induced arrhythmia. Analogue 10 with the 8-(2-morpholin-4-yl)-ethylamino group was the most active (ED(50) = 3.9 mg/kg and TI = 59.8), which may indicate that this substituent is preferably important for the antiarrhythmic effect. Only compound 11 with the 8-(2-diethylamino)-ethylamino group significantly decreased the systolic (20.4-28.1%) and diastolic (23.4-33.2%) pressure, but this effect lasted for only 1-5 min. The pharmacologically active compounds 9-11 with the phenylpiperazine moiety showed affinity for α(1)-receptors (K(i) = 0.143-0.383 μM), but the other compounds were almost (12-15) or completely (8) inactive at this site. Compounds 9-11 and 13-15 displayed moderate to low affinity for α(2)-receptors (K(i) = 0.36-2.7 μM).     

Antiarrhythmic action of rilmenidine on adrenaline-induced arrhythmia via central imidazoline receptors in halothane-anaesthetized dogs.

1. To elucidate the role of central imidazoline receptors in the genesis of adrenaline-induced arrhythmias under halothane anaesthesia, we investigated the effects of rilmenidine, a selective agonist at imidazoline receptors, on this type of arrhythmia in dogs. Rilmenidine (1, 3, 10 micrograms kg-1, i.v.) did not affect basal haemodynamic parameters (heart rate and blood pressure), but dose-dependently inhibited adrenaline-induced arrhythmias under halothane anaesthesia. 2. Although, rilmenidine has a weak affinity for alpha(2)-adrenoceptors, pretreatment with idazoxan (10 micrograms kg-1, intracisternally i.c.), an imidazoline receptor antagonist which has also alpha(2)-adrenoceptor blocking potency, blocked the antiarrhythmic effect of rilmenidine (10 micrograms kg-1, i.v.). In contrast, pretreatment with rauwolscine (20 micrograms kg-1, i.c.), a classical alpha(2)-adrenoceptor antagonist with little affinity for imidazoline receptors, did not affect the effect of rilmenidine (10 micrograms kg-1, i.v.). Furthermore, bilateral vagotomy completely blocked the antiarrhythmic action of rilmenidine (10 micrograms kg-1, i.v.). 3. It is suggested that the antiarrhythmic action of rilmenidine is due to the activation of central imidazoline receptors and that vagal tone is critical for this action of rilmenidine.     

trans-4-[4-(Methoxyphenyl)cyclohexyl]-1-arylpiperazines: a new class of potent and selective 5-HT(1A) receptor ligands as conformationally constrained analogues of 4-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]-1-arylpiperazines.

The present paper concerns the influence of conformational parameters on the recognition by rat 5-HT1A receptors of derivatives 4-[3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)propyl]-1-(2-pyridinyl)piperazine (1a) and 3-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-N-[2-(2-pyridyloxy)ethyl]propanamine (3b), two highly potent and selective 5-HT1A receptor ligands. Fifteen corresponding flexible and rigid analogues were prepared following several synthetic routes and were tested in binding assays with radioligands at 5-HT1A, D2, and alpha1 receptors from rat brain membranes. Among the new derivatives emerged trans-4-[4-(3-methoxyphenyl)cyclohexyl]-1-(2-pyridinyl)piperazine (trans-8a) and trans-N-[4-(3-methoxyphenyl)cyclohexyl]-2-(2-pyridyloxy)ethylamine (trans-8b). These compounds can be considered as conformationally constrained analogues of compounds 1a and 3a, respectively. In fact, compounds trans-8a and trans-8b showed a marked enhancement in 5-HT1A receptor affinity when compared to the corresponding cis isomers. Because compound trans-8a was a potent and selective 5-HT1A ligand (K(i), nM: 5-HT1A = 0.028, D2 = 2194, alpha1 = 767), it was chosen as a lead to prepare other analogues that were tested at 5-HT1A, D2, and alpha1 receptors from rat brain membranes, showing high affinity at the 5-HT1A and selectivity vs D2 and alpha1 receptors. Selected compounds were tested for their affinity at the human cloned 5-HT1A, alpha1a, alpha1b, alpha1d receptor subtypes. They were also submitted to the [35S]GTPgammaS binding assay stimulating the 5-HT1A receptor-mediated G-protein activation, therefore behaving as full or as partial agonists. Finally, the ability of iv administration of trans-8a to induce fore-paw treading in rats was evaluated in comparison with 8-OH-DPAT. Although the affinity (K(i)) and in vitro activity (pD'2) of trans-8a at the 5-HT1A receptor were higher than those of 8-OH-DPAT, the compound was less potent than the reference standard in inducing the symptom.     

Mixed Dopaminergic/Serotonergic Properties of Several 2-Substituted 4-[2-(5-Benzimidazole)ethyl]-1-arylpiperazines

A series of substituted 4-[2-(5-benzimidazole)ethyl]-arylpiperazines was synthesized by introducing different substituents into position 2 of benzimidazole ring of 4-[2-(N,N-di-n-propyl-amino)ethyl]-1,2-diaminobenzenes. They were evaluated for in vitro binding affinity at the D₁ and D₂ dopamine and 5-HT_1A serotonin receptors using synaptosomal membranes of the bovine caudate nuclei and hippocampi, respectively. Tritiated SCH 23390 (D₁ receptor-selective), spiperone (D₂ receptor selective) and 8-OH-DPAT (5-HAT_1A receptor selective) were employed as the radioligands. Only compound 6 expressed a moderate binding affinity at the dopamine D₁ receptor, while the remaining ligands were inefficient or weak competitors of [³H]SCH 23390. Compound 12 was an absolutely inactive competitor of all three radioligands. Also, compound 7 was an inefficient displacer of [³H]-8-OH-DPAT. Compound 19 with a K_i value of 3.5 nM was the most potent competitor of [³H]spiperone and compound 13 (K_i = 3.3 nM) was the most efficient in displacing [³H]-8-OH-DPAT from the 5-HAT_1A serotonin receptor. Ligands 5, 6, 8–11 , and 13–20 expressed mixed dopaminergic/serotonergic activity in nanomolar range of concentrations with varying affinity ratios which strongly depended on the properties of the substituents introduced into position 2 of benzimidazole ring of the parent compounds.     

Evaluation of anticonvulsant activity of novel pyrrolidin-2-one derivatives

BackgroundThe aim of this study was to examine the anticonvulsant activity of some novel pyrrolidin-2-one derivatives with considerable affinity to serotonin 5-HT_1A and α₁-adrenergic receptors.MethodsThe maximal electroshock-induced seizure (MES) and pentetrazole (PTZ)-induced seizure models in mice were performed.ResultsAs a results of the conducted studies, three compounds showing anticonvulsant activity were selected. The EP-40 molecule significantly reduced incidence of seizures in the maximal electroshock test. The EP-42 and EP-46 compounds demonstrated activity in the pentetrazole-induced seizures.ConclusionThe results may indicate that the decrease in the susceptibility to seizures induced by the new pyrrolidin-2-one derivatives is related to the significant affinity to serotonergic or α₁-adrenergic receptors. Also putative mechanism of action of the test compounds can be linked with their GABA-ergic activity, because these novel derivatives are GABA analogs.