Mechanisms of morphine-venlafaxine interactions in diabetic neuropathic pain model.

BACKGROUND: we investigated the possible mechanisms involved in the interactions of venlafaxine (VFX), a selective serotonin and noradrenaline reuptake inhibitor, and morphine (MRF), an opioid receptor agonist, after acute and chronic VFX treatment in diabetic neuropathic pain model (DNPM). METHODS: The studies were performed on male rats. The changes in nociceptive thresholds were determined by using mechanical stimuli (the Randall-Selitto and the von Frey tests). Diabetes was induced by intramuscular administration of streptozotocin. In order to investigate the mechanism of interaction, animals were also pretreated with naloxone (NLX), a nonselective opioid antagonist, yohimbine (YOH), a nonselective α2-adrenergic antagonist, and p-chloroamphetamine (PCA), a neurotoxin that destroys serotonergic neurons. The µ-opioid receptors' density was determined with the use of radioligand binding assay. RESULTS: VFX potentiated antinociceptive action of MRF after acute administration of VFX and this effect was decreased by pretreatment of NLX, YOH and PCA. On the contrary, VFX administered for 21 days prior to MRF significantly decreased the analgesic action of MRF; this effect was augmented only after YOH pretreatment. Also, 21-days administration of VFX caused decreasing tendency in the number of µ-opioid receptors in the brain stem. CONCLUSIONS: The results of our study show that single administration of VFX potentiates antinociceptive action of morphine in DNPM. This effect is probably mediated by both, noradrenergic and serotonergic systems. On the other hand, 21-days administration of VFX significantly decreases analgesic action of MRF. Moreover, there is a possibility that VFX acts as an antagonist of N-methyl-d-aspartate receptors.

Serotonin transporter activity of imidazolidine-2,4-dione and imidazo[2,1-f]purine-2,4-dione derivatives in aspect of their acid-base properties.

Affinities of arylpiperazinylalkyl derivatives of imidazo[2,1-f]purine-2,4-dione and imidazolidine-2,4-dione for serotonin transporter and their acid-base properties were evaluated. The dissociation constant (pK(a)) of compounds 1-22 were determinated by potentiometric titration and calculated using pKalc 3.1 module of the Pallas system. The data from experimental methods and computational calculations were compared and suitable conclusions were reached.

Antiarrhythmic properties of phenylpiperazine derivatives of phenytoin with α1-adrenoceptor affinities.

An association between α(1)-adrenoceptor affinities, hERG K(+)-antagonistic properties and antiarrhythmic activities for a series of phenylpiperazine derivatives of hydantoin (2a-21a) was investigated. New compounds were synthesized and tested for their affinity for α(1)-adrenoceptors in radioligand binding assay using [(3)H]-prazosin as a selective radioligand. Antiarrhythmic activities in adrenaline- and barium chloride-induced arrhythmia models, an influence of the phenylpiperazine derivatives on the ECG-components and blood pressure were tested in vivo in normotensive rats. The hERG K(+)-antagonistic properties of the most potent antiarrhythmic agents were investigated in silico by the use of program QikProp. The highest α(1)-adrenoceptor affinity (K(i)=4.7 nM) and the strongest antiarrhythmic activity in adrenaline induced arrhythmia (ED(50)=0.1 mg/kg) was found for 1-(4-(4-(2-methoxyphenyl)piperazin-1-yl)butyl)-3-methyl-5,5-diphenylimidazolidine-2,4-dione hydrochloride (19a). The results indicated a significant correlation between α(1)-AR affinities (pK(i)) and antiarrhythmic activity (ED(50)) in adrenaline model (R(2)=0.92, p <0.005). Influence of the examined phenylpiperazine hydantoin derivatives on hERG K(+) channel, predicted by means of in silico methods, suggested their hERG K(+)-blocking properties.

Derivatives of pyrrolo[3,4-d]pyridazinone, a new class of analgesic agents.

A series of N2-{2-[4-aryl(benzyl)-1-piperazinyl(piperidinyl)]ethyl}pyrrolo[3,4-d]pyridazinones 4 and related derivatives 5 were synthesized as potential analgesic agents. The structures of the new compounds were elucidated by micro, spectral and X-ray analysis. Analgesic activity of the compounds was investigated in the phenylbenzoquinone induced 'writhing' and 'hot plate' test in mice and at radioligand binding assay. At 'writhing' test all compounds, without exception, were more active than acetylsalicylic acid (ASA) with ED(50) values ranging from 0.04 to 11 mg/kg (i.p.) (ED(50) for ASA--39.15 mg/kg). Analgesic effect at the 'hot plate' test was observed for three compounds 4c,e,f at the dose 3-5 times higher then that of morphine (ED(50)-3.39 mg/kg). At radioligand binding assay of 4c,e,f only compound 4f exhibited affinity for the µ-opioid receptors similar to that of Tramadol. The acute toxicity of the pyrrolopyridazinones 4, 5 were also studied and non toxic effect was observed at the 2000 mg/kg (5a 1420 mg/kg) i.p. dose level. On the basis of the available pharmacological data S-A relationship is discussed. The preferred conformational characteristic of 4, taken 4c as an example, was also described.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT(1A) activity. part 3.

A number of 4-aryl-5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine with 3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole or 2-methyl-3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole residues were synthesized for further investigation of SAR in a group of pyrido[1,2-c]pyrimidine derivatives with dual 5-HT(1A)/SERT activity. Compounds 8a-8p were found to be potent ligands for both 5-HT(1A) and SERT with K(i) ranging from 28,3 to 642 nM and 42,4 nM-1,8 µM, respectively. Moreover compounds 8a, 8b, 8c, 8d, 8e and 8g were found to be selective agonists, while 8i as an antagonist of 5-HT(1A) presynaptic receptors in the inducible hypothermia test in mice.

Synthesis and pharmacological evaluation of new 5-(cyclo)alkyl-5-phenyl- and 5-spiroimidazolidine-2,4-dione derivatives. Novel 5-HT1A receptor agonist with potential antidepressant and anxiolytic activity.

The synthesis of 5-(cyclo)alkyl-5-phenyl- and 5-spiroimidazolidine-2,4-dione derivatives with an arylpiperazinylpropyl moiety (12-23) and their in vitro and in vivo pharmacological properties and molecular characteristics were described. The investigated compounds exhibited high affinity for 5-HT(1A) (13-22) and 5-HT(2A) (18, 20, 21, 23) receptors and diversified pharmacological profile. Compounds 17, 20 and 22 showed antagonistic, partial agonistic and agonistic activity, respectively, toward 5-HT(1A) receptor and they were investigated as potential antidepressants and/or anxiolytics. The most interesting compound 22 (1-[3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl]-3',4'-dihydro-2'H-spiro[imidazolidine-4,1'-naphthalene]-2,5-dione), a pre- and postsynaptic 5-HT(1A) receptor agonist produced an antidepressant-like effect, which was more pronounced than that of imipramine in the forced swim test in mice, without affecting locomotor activity. Moreover, compound 22 produced a weak anxiolytic-like effect in the four-plate test in mice. Molecular docking studies of compound 22 to the homology model of the 5-HT(1A) receptor showed that a 3',4'-dihydro-2'H-spiro[imidazolidine-4,1'-naphthalene]-2,5-dione moiety played an important role in stabilizing the ligand-receptor complex.

Alterations in hippocampal calcium-binding neurons induced by stress models of depression: a preliminary assessment.

In this study, the neuropathological changes induced by chronic unpredictable stress (CUS) and chronic mild stress (CMS) in calbindin D-28K (CB) and parvalbumin (PV) immunoreactive neurons in the rat hippocampus were demonstrated. We used immunohistochemical techniques to quantify the numerical density and morphological changes of PV immunoreactive and CB immunoreactive neurons in the dentate gyrus (DG) and the CA1 and CA3 regions of the hippocampus. We also assessed cell proliferation (Ki-67) and apoptotic processes (active caspase-3) in the DG. We found a significant decrease (16.6% for CUS and 13.3% for CMS) in the numerical density of granule cells (GC), alterations in the CB immunoreactive cells of the GC in the DG and an impairment of mossy fiber CB immunolabelling in the CA3. These changes were not accompanied by a decrease in Ki-67 labeling or the level of caspase-3 in the DG. These data indicate a stress-induced reduction of calcium binding neuron parameters, which may be related to the behavioral paradigms exhibited in these models.

Synthesis and preliminary pharmacological evaluation of imidazo[2,1-f]purine-2,4-dione derivatives.

A series of N-8-arylpiperazinylpropyl derivatives of 1,3-dimethyl-(1H,8H)-imidazo[2,1-f]purine-2,4-dione (2-10) and amide derivatives of 1,3-dimethyl-6,7-dihydroimidazo[2,1-f]purine-2,4-(1H,3H)-dione-7-carboxylic acid (11-13) were synthesized. Compounds (2-10) evaluated in vitro were potent 5-HT(1A) receptor ligands. Preclinical studies indicated that 8-[3-(N4-phenyl)-piperazin-N1-yl-propyl]-1,3-dimethyl-(1H,8H)-imidazo[2,1-f]purine-2,4-dione (2) exerts anxiolytic-like activity in the four-plate test in mice; however its effect was weaker, than that produced by Diazepam. This compound and 8-[3-(N4-2'-metoxyphenyl)-piperazin-N1-yl-propyl]-1,3-dimethyl-(1H,8H)-imidazo[2,1-f]purine-2,4-dione (3) behaved like antidepressants in the forced swimming test in mice; and their activity in that model was comparable with the effect of Imipramine. The obtained results suggested that the long-chain arylpiperazines (LCAPs) linked to tricyclic derivatives of the theophylline remain a worthy of future research for obtaining new derivatives with potential anxiolytic/antidepressant activity.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT1A activity: part 2.

Derivatives of 4-aryl-5,6,7,8-tetrahydro-pyrido[1,2-c]pyrimidine were synthesized. These compounds contain the 3-(4-piperidyl)-1H-indole residue or its 5-methoxy or 2-methyl derivative. In vitro binding tests were performed to determine the affinity of the compounds for the 5-HT(1A) receptor and serotonin transporter (SERT) proteins in the rat brain cortex. In vivo studies, particularly the inducible hypothermia test and forced swimming test, were conducted to determine agonistic/antagonistic activity with pre- and postsynaptic 5-HT(1A) receptors. Molecular modeling techniques were used to determine the binding modes of the selected compounds at the 5-HT(1A) receptor and SERT. The SAR analysis showed that the presence of the 3-(4-piperidyl)-1H-indole group or its 5-methoxy derivative, as well as a para substitution with -OCH(3) or -F in the aryl ring of 4-aryl-5,6,7,8-tetrahydro-pyrido[1,2-c]pyrimidine, results in an increased affinity for both the 5-HT(1A) receptors and SERT. In contrast, the presence of the 2-methyl-3-(4-piperidyl)-1H-indole group resulted in a considerable decrease in binding affinity.

Evaluation of oxidative status and depression-like responses in Brown Norway rats with acute myeloid leukemia.

It has been proved that oxidative stress increases when leukemia is accompanied by depression. This fact may indicate the role of oxidative stress in the development of depression in cancer patients. The aim of this study was to determine whether the acute myeloid leukemia of Brown Norway rats, which is accompanied by oxidative stress, evoked behavioral and receptor changes resembling alterations characteristic of rat models of depression. The rats were divided into two groups: leukemic rats and healthy control. Leukemia was induced through intraperitoneal injection of 10(7) promyelocytic leukemia cells to the Brown Norway rats. Depression-like behavior was evaluated in the forced swim test at 30 or 34 days after leukemic cells injection. The rats were killed after the evaluation and the spleen, brain cortex and hippocampus were excised. The red-ox state was assessed in homogenates of tissues by measuring total glutathione (GSH) content, the ferric ion reducing ability of plasma (FRAP) level, expression of heme oxygenase-1 (HO-1), biliverdin reductase (BvR) and ferritin mRNA, superoxide dismutase (SOD) activity, as well as malondialdehyde (MDA) concentration. Radioligand binding assay was used to assess of the effect of leukemia on cortical receptors. Leukemic cells were identified using RM-124 antibody by FACS Calibur flow cytometry. Leukemia influenced locomotory activity as well as forced swim test behavior in a 34-day series of experiments. Signs of oxidative stress in leukemic rats were observed in each examined stage of leukemia development. The FRAP values and glutathione contents, were significantly lowered whereas HO-1 mRNA expression, and malonodialdehyde concentrations were significantly increased in the spleen and brain structures of leukemic rats in comparison with the healthy controls. A significant increase in the potency of glycine to displace [(3)H]L-689,560 from the strychnine-insensitive glycine site of the N-methyl-D-aspartic (NMDA) receptors receptor complex in cortical homogenates of the leukemic rats in 30- and 34-day experimental series was observed in comparison with the control. Upregulation of 5-HT(2A) receptors was observed in rat cortex after 30 days of leukemia development but not in 34-days series compared with the control. It is concluded that disturbances in antioxidant system in brain cortex were accompanied by an activation of glycine sites of the NMDA receptor complex, regardless of stage of leukemia development, which are characteristic of model of depression. Findings of our study demonstrate the link between glutamatergic activity, oxidative stress and leukemia.

Preliminary evaluation of pharmacological properties of some xanthone derivatives.

A series of xanthone derivatives were synthesized and examined for electrocardiographic, antiarrhythmic, hypotensive and anticonvulsant activities as well as for alpha(1)- and beta(1)-adrenergic binding affinities. Among the investigated compounds, some of them exhibited significant antiarrhythmic and/or hypotensive activity. The data obtained via receptor binding assay are in agreement with pharmacological results and could explain antiarrhythmic and/or hypotensive activity of the newly synthesized structures.

The involvement of serotonergic system in the antidepressant effect of zinc in the forced swim test.

Recent preclinical data indicated the antidepressant-like activity of zinc in different tests and models of depression. The present study investigates the involvement of the serotonergic system in zinc activity in the forced swim test (FST) in mice and rats. The combined treatment of sub-effective doses of zinc (hydroaspartate, 2.5 mg Zn/kg) and citalopram (15 mg/kg), fluoxetine (5 mg/kg) but not with reboxetine (2.5 mg/kg) significantly reduces the immobility time in the FST in mice. These treatments had no influence on the spontaneous locomotor activity. Moreover, while the antidepressant-like effect of zinc (5 mg/kg) in the FST was significantly blocked by pretreatment with inhibitor of serotonin synthesis, p-chlorophenylalanine (pCPA, 3x200 mg/kg), 5HT-2(A/C) receptor antagonist, ritanserin (4 mg/kg) or 5HT-1A receptor antagonist, WAY 1006335 (0.1 mg/kg), the zinc-induced reduction in the locomotor activity was not affected by these serotonin modulator agents. These results indicate the specific involvement of the serotonergic system in antidepressant but not the motion behavior of zinc in mice. Also, an increase in the swimming but not climbing parameter of the rat FST observed following zinc administration (2.5 and 5 mg Zn/kg) indicates the serotonin pathway participation. This present data indicates that the antidepressant-like activity of zinc observed in the FST involves interaction with the serotonergic system.

Synthesis and adrenolytic activity of 1-(1H-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethyl]amino}propan-2-ol and its enantiomers. Part 1.

The synthesis of (2RS)-1-(1H-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethyl]amino}propan-2-ol ((RS)-9) and its enantiomers has been described and tested for electrocardiographic, antiarrhythmic, hypotensive and spasmolytic activities as well as for alpha(1)-, alpha(2)- and beta(1)-adrenoceptors' binding affinities. All compounds significantly decrease systolic and diastolic blood pressure, and possess antiarrhythmic activity and affinity to alpha(1)-, alpha(2)- and beta(1)-adrenoceptors. The results suggest that the antiarrhythmic and hypotensive effects of these compounds are related to their adrenolytic but not spasmolytic properties.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT1A activity, part 1.

A series of new derivatives of 4-aryl-pyrido[1,2-c]pyrimidine containing the 3-(4-piperidyl)-1H-indole residue or its 5-methoxy derivative were synthesized. They were characterized (i) in vitro by binding to 5-HT(1A) receptors and 5-HT transporter proteins in rat brain cortex membranes and (ii) in vivo in the mouse by induced hypothermia and forced swimming models for antagonist/agonist activity against the 5-HT(1A) autoreceptors and postsynaptic 5-HT(1A) receptors, respectively. Structure activity relationship evaluation indicated that the presence of the 3-(4-piperidyl)-1H-indole residue and ortho- or para-substituents with -F or -CH(3) groups in the aryl ring as well as an unsubstituted aryl in the 4-aryl-pyrido[1,2-c]pyrimidine moiety promoted low K(i) values for both receptors. In contrast, the presence of a 5-methoxy-3-(4-piperidyl)-1H-indole residue as well as -Cl or -OCH(3) substituents at the para position markedly reduced the receptor affinity.

Specific binding sites for progesterone and 17beta-estradiol in cells of Triticum aestivum L.

The presence and location of specific binding sites for progesterone and 17beta-estradiol in cells of wheat were estimated using radioligand binding assay. Membrane and cytosolic fractions of non-vernalized and vernalized plants were tested using tritium-labelled ligands. Specific binding of [(3)H]progesterone and [(3)H]17beta-estradiol occurs in wheat cells. The binding sites are located in membranes and in the cytosol. Specific binding of [(3)H]17beta-estradiol is higher in the membranes than in the cytosol. Specific binding of both ligands in the cytosolic fraction is higher in vernalized plants than in non-vernalized ones. The possibility of the occurrence of steroid binding proteins specific for progesterone and 17beta-estradiol, putative steroid receptors for these steroids in Triticum aestivum L., is discussed.

Lack of NMDA-AMPA interaction in antidepressant-like effect of CGP 37849, an antagonist of NMDA receptor, in the forced swim test.

The NMDA receptor antagonist, CGP 37849-induced reduction in immobility time in the forced swim test in mice was not antagonized by pre-treatment with the AMPA receptor antagonist NBQX. This is the first demonstration of the antidepressant effect of the NMDA antagonist not being dependent on the AMPA transmission.

Antidepressant-like effect of chromium chloride in the mouse forced swim test: involvement of glutamatergic and serotonergic receptors.

Chromium (Cr) (III), an essential microelement of living organisms, was reported to exhibit potential antidepressant properties in preclinical and clinical studies. The aim of the present study was to examine the effect of CrCl(3) ip administration in the forced swim test (FST) in mice and the involvement of glutamatergic and serotonergic receptors in the antidepressant-like activity of chromium. CrCl(3) in a dose of 12 mg/kg, but not in doses of 6 or 32 mg/kg, reduced the immobility time in the FST. The locomotor activity was reduced by CrCl(3) in a dose of 32 mg/kg. Moreover, the reduction of the immobility time induced by the active dose (12 mg/kg) of CrCl(3) was completely abolished by NBQX (10 mg/kg; an antagonist of the AMPA receptor) pretreatment and partially inhibited by ritanserin (4 mg/kg; an antagonist of 5-HT(2A/C) receptor), WAY 1006335 (0.1 mg/kg; an antagonist of 5-HT(1A) receptor) and N-methyl-D-aspartate (75 mg/kg; agonist of NMDA receptor) administration. The present study demonstrates the antidepressant-like activity of chromium in the mouse FST and indicates the major role of the AMPA receptor and participation of NMDA glutamatergic and 5-HT(1) and 5-HT(2A/C) serotonin receptors in this activity.

Synthesis, physicochemical and anticonvulsant properties of new N-phenylamino derivatives of 2-azaspiro[4.4]nonane- and [4.5]decane-1,3-diones: part V.

The synthesis, physicochemical and pharmacological properties of new N-phenylamino derivatives of 2-azaspiro[4.4]nonane-1,3-dione (8-10), 2-azaspiro[4.5]decane-1,3-dione (11-18) and 3-cyclohexyl-pyrrolidine-2,5-dione (19, 20) derivatives were described. The anticonvulsant properties of those compounds were examined by a maximal electroshock (MES) and a pentylenetetrazole (scPTZ) tests, and their neurotoxicity was determined using a rota-rod test. The most active was N-[(2,4-dichlorophenyl)-amino]-2-azaspiro[4.4]nonane-1,3-dione (9), which exhibited anti-seizure properties in the MES model at a dose of 100mg/kg in mice and at a dose of 30mg/kg in rats. To explain the possible mechanism of action, for chosen active derivatives N-[(2,4-dichlorophenyl)-amino]-2-azaspiro[4.4]nonane-1,3-dione (9), N-[(4-bromophenyl)-amino]-2-azaspiro[4.4]nonane-1,3-dione (10), N-[(2,4-dichlorophenyl)-amino]-2-azaspiro[4.5]decane-1,3-dione (12) and N-[(4-bromophenyl)-amino]-2-azaspiro[4.5]decane-1,3-dione (13) their influence on GABA(A) receptors were tested in vitro. Moreover, for all compounds obtained the lipophilic properties were determined by use of RP-HPLC method.

Activation of the NMDA/glutamate receptor complex antagonizes the NMDA antagonist-induced antidepressant-like effects in the forced swim test.

The antidepressant activity of NMDA receptor antagonists has been demonstrated, and their mechanism of action was based on the assumption of their selectivity for the NMDA receptor only. However, no direct evidence for the NMDA receptor role in this activity was demonstrated. Now, in order to prove the NMDA pathway of antidepressant-like action of the NMDA antagonists in the mouse forced swim test (FST) we examined if antidepressant activity of NMDA receptor antagonists is mediated by NMDA receptors and whether the activation of different modulatory sites of the NMDA receptor complex influence the action of the antagonists of different sites of NMDA receptor. In our study, we used two NMDA ligands: competitive NMDA glutamate site antagonist CGP 37849, and glycineB antagonist L-701,324; both at doses found to be effective in the FST. The antidepressant-like activity of the compounds was abolished by the N-methyl-D-aspartic acid (NMDA) or by D-serine co-treatment. Ligands at the doses active in the FST did not alter locomotor activity. The present study indicates the major role of the NMDA/glutamate pathway in the antidepressant-like activity of NMDA antagonists in the mouse FST.

Medium supplementation with zinc enables detection of imipramine-induced adaptation in glycine/NMDA receptors labeled with [3H]L-689,560.

Antidepressant drugs after chronic administration induce adaptive changes in the NMDA receptor complex. Radioligand-receptorbinding studies using [3H]5,7-dichlorokynurenic acid demonstrated a "down-regulation" of the glycine site/NMDA receptor following chronic treatment with antidepressants and electroconvulsive shock. However, binding procedure using this radioligand is time consuming because it requires the use of centrifugation method in the separation process. The introduction of a new radioligand of glycine/NMDA receptor, [3H]L-689,560 enables the application of a rapid filtration method. In the present study we demonstrate that 2-week treatment with imipramine (15 mg/kg ip) did not evoke alterations in specific [3H]L-689,560 binding and in IC50 value of glycine in displacing [3H]L-689,560 binding in the mouse or rat cortex. However, longer, a 4-week treatment with imipramine induced a significant 71% increase in IC50 value in displacing [3H]L-689.560 binding in the mouse cortex. Moreover, the presence of zinc in the incubation media, dose-dependently enhances detection of imipramine-induced increase in IC50 value of glycine in displacing [3H]L-689,560 binding in the rat cortex. The present data indicate that: (1) [3H]L-689,560 may be a suitable ligand for assessing adaptation of the glycine/NMDA sites and (2) the presence of zinc enhances detection of imipramine-induced reduction of glycine affinity for glycine/NMDA receptors labeled with [3H]L-689,560 which further indicates a significance of zinc in the mechanism of antidepressant treatment.