A valepotriate-enriched fraction from Valeriana glechomifolia decreases DNA methylation and up-regulate TrkB receptors in the hippocampus of mice.

DNA methylation, an epigenetic modification that mediates gene silencing, has been shown to play a role in the neurobiology of major depression. Studies suggested that terpenes inhibit DNA methylation and increase gene expression. The present study investigated the involvement of DNA methylation in the antidepressant-like activity of diene valepotriates, non-glicosilated carbocyclic iridoids that comprise a family of terpenes obtained from Valeriana glechomifolia. The antidepressant-like effect of diene valepotriates acute administration (5 mg/kg, p.o.) in mice submitted to the forced swimming test was followed by a decrease in global DNA methylation in animals' hippocampus (but not in the pre-frontal cortex). Mice pretreatment with anysomicin (a protein synthesis inhibitor) and K252a (an inhibitor of Trk receptors) attenuated diene valepotriates-induced antidepressant-like effect in the forced swimming test. Diene valepotriates elicited an upregulation in the TrkB receptor and a tendency to increase BDNF levels in mice hippocampus. These results demonstrate that DNA methylation could be an in vivo molecular target of diene valepotriates. The diene valepotriates-triggered reduction in hippocampal DNA methylation is accompanied by increased protein synthesis, which is involved in its antidepressant-like activity. Furthermore, BDNF-mediated TrkB signaling may contribute for diene valepotriates antidepressant-like effect.

LASSBio-1422: a new molecular scaffold with efficacy in animal models of schizophrenia and disorders of attention and cognition.

Aiming to identify new antipsychotic lead-compounds, our group has been working on the design and synthesis of new N-phenylpiperazine derivatives. Here, we characterized LASSBio-1422 as a pharmacological prototype of this chemical series. Adult male Wistar rats and CF1 mice were used for in-vitro and in-vivo assays, respectively. LASSBio-1422 [1 and 5 mg/kg, postoperatively (p.o.)] inhibited apomorphine-induced climbing as well as ketamine-induced hyperlocomotion (1 and 5 mg/kg, p.o.), animal models predictive of efficacy on positive symptoms. Furthermore, LASSBio-1422 (5 mg/kg, p.o.) prevented the prepulse impairment induced by apomorphine, (±)-2,5-dimethoxy-4-iodoamphetamine, and ketamine, as well as the memory impairment induced by ketamine in the novel object-recognition task at the acquisition, consolidation, and retrieval phases of memory formation. Potential extrapyramidal side-effects and sedation were assessed by catatonia, rota-rod, locomotion, and barbiturate sleeping time, and LASSBio-1422 (15 mg/kg, p.o.) did not affect any of the parameters observed. Binding assays showed that LASSBio-1422 has a binding profile different from the known atypical antipsychotic drugs: it does not bind to AMPA, kainate, N-methyl-D-aspartate, glicine, and mGluR2 receptors and has low or negligible affinity for D1, D2, and 5-HT2A/C receptors, but high affinity for D4 receptors (Ki=0.076 µmol/l) and, to a lesser extent, for 5-HT1A receptors (Ki=0.493 µmol/l). The antagonist action of LASSBio-1422 at D4 receptors was assessed through the classical GTP-shift assay. In conclusion, LASSBio-1422 is effective in rodent models of positive and cognitive symptoms of schizophrenia and its ability to bind to D4 and 5-HT1A receptors may at least in part explain its effects in these animal models.

Is Forced Swimming Immobility a Good Endpoint for Modeling Negative Symptoms of Schizophrenia? - Study of Sub-Anesthetic Ketamine Repeated Administration Effects.

Immobility time in the forced swimming has been described as analogous to emotional blunting or apathy and has been used for characterizing schizophrenia animal models. Several clinical studies support the use of NMDA receptor antagonists to model schizophrenia in rodents. Some works describe the effects of ketamine on immobility behavior but there is variability in the experimental design used leading to controversial results. In this study, we evaluated the effects of repeated administration of ketamine sub-anesthetic doses in forced swimming, locomotion in response to novelty and novel object recognition, aiming a broader evaluation of the usefulness of this experimental approach for modeling schizophrenia in mice. Ketamine (30 mg/kg/day i.p. for 14 days) induced a not persistent decrease in immobility time, detected 24h but not 72h after treatment. This same administration protocol induced a deficit in novel object recognition. No change was observed in mice locomotion. Our results confirm that repeated administration of sub-anesthetic doses of ketamine is useful in modeling schizophrenia-related behavioral changes in mice. However, the immobility time during forced swimming does not seem to be a good endpoint to evaluate the modeling of negative symptoms in NMDAR antagonist animal models of schizophrenia.

LASSBio-579, a prototype antipsychotic drug, and clozapine are effective in novel object recognition task, a recognition memory model.

Previous studies on the N-phenylpiperazine derivative LASSBio-579 have suggested that LASSBio-579 has an atypical antipsychotic profile. It binds to D2, D4 and 5-HT1A receptors and is effective in animal models of schizophrenia symptoms (prepulse inhibition disruption, apomorphine-induced climbing and amphetamine-induced stereotypy). In the current study, we evaluated the effect of LASSBio-579, clozapine (atypical antipsychotic) and haloperidol (typical antipsychotic) in the novel object recognition task, a recognition memory model with translational value. Haloperidol (0.01 mg/kg, orally) impaired the ability of the animals (CF1 mice) to recognize the novel object on short-term and long-term memory tasks, whereas LASSBio-579 (5 mg/kg, orally) and clozapine (1 mg/kg, orally) did not. In another set of experiments, animals previously treated with ketamine (10 mg/kg, intraperitoneally) or vehicle (saline 1 ml/100 g, intraperitoneally) received LASSBio-579, clozapine or haloperidol at different time-points: 1 h before training (encoding/consolidation); immediately after training (consolidation); or 1 h before long-term memory testing (retrieval). LASSBio-579 and clozapine protected against the long-term memory impairment induced by ketamine when administered at the stages of encoding, consolidation and retrieval of memory. These findings point to the potential of LASSBio-579 for treating cognitive symptoms of schizophrenia and other disorders.

Effects of diene valepotriates from Valeriana glechomifolia on Na+/K+-ATPase activity in the cortex and hippocampus of mice.

Diene valepotriates obtained from Valeriana glechomifolia present antidepressant-like activity, mediated by dopaminergic and noradrenergic neurotransmissions. Also, previous studies have shown inhibitory activity of diene valepotriates towards Na(+)/K(+)-ATPase from the rat brain in vitro. Nevertheless, in vivo studies regarding the action of diene valepotriates on this enzyme are still lacking. Considering that Na(+)/K(+)-ATPase cerebral activity is involved in depressive disorders, the aim of this study was to investigate the effects of acute (5 mg/kg, p. o.) and repeated (5 mg/kg, p. o., once a day for three days) diene valepotriate administration on Na(+)/K(+)-ATPase activity in the cortex and hippocampus of mice submitted or not submitted to the forced swimming test. In addition, the protein expression of Na(+)/K(+)-ATPase α1, α2, and α3 isoforms in the cortex of mice repeatedly treated with diene valepotriates (and submitted or not submitted to the forced swimming test) was investigated. Diene valepotriates significantly decreased mice immobility time in the forced swimming test when compared to the control group. Only the animals repeatedly treated with diene valepotriates presented increased Na(+)/K(+)-ATPase activity in the cerebral cortex, and the exposure to the forced swimming test counteracted the effects of the diene valepotriates. No alterations in the hippocampal Na(+)/K(+)-ATPase activity were observed. Repeated diene valepotriate administration increased the cortical content of the α2 isoform, but the α3 isoform protein expression was augmented only in mice repeatedly treated with diene valepotriates and forced to swim. Mice treated with the vehicle and submitted to the forced swimming test also presented an increase in the content of the α2 isoform, but no alterations in Na(+)/K(+)-ATPase activity. These results suggest that cortical Na(+)/K(+)-ATPase may represent a molecular target of the diene valepotriates in vivo and long-term regulatory mechanisms are involved in this effect. Also, the forced swimming test per se influences the protein expression of Na(+)/K(+)-ATPase isoforms and counteracts the effects of the diene valepotriates on cortical Na(+)/K(+)-ATPase.

Acylphloroglucinol derivatives from Hypericum andinum: antidepressant-like activity of andinin A.

A new dimeric acylphloroglucinol derivative, andinin A (1), was isolated from the underground plant parts of Hypericum andinum, along with three known dimeric acylphloroglucinols, uliginosin A (2), uliginosin B (3), and isouliginosin B (4). The structure of 1 was elucidated using 1D and 2D NMR and MS experiments and by comparison with previously reported data for Hypericum dimeric acylphloroglucinols. Andinin A (1) displayed antidepressant-like activity in a mouse forced-swimming test when administered orally at doses of 3, 10, and 30 mg/kg.

Study of antidepressant-like activity of an enriched phloroglucinol fraction obtained from Hypericum caprifoliatum.

CONTEXT: Hypericum caprifoliatum Cham & Schlecht (Guttiferae) extracts have a potential antidepressant-like effect in rodents. However, the molecular mechanisms by which these extracts exert this effect remain unclear. OBJECTIVE: This study evaluated the effect of HC1, a fraction obtained from H. caprifoliatum enriched in phloroglucinol derivatives, on the Na⁺, K⁺ ATPase activity in mouse brain and verified the influence of veratrine on the effect of HC1 in the forced swimming test (FST). MATERIALS AND METHODS: Veratrine (0.06 mg/kg) and HC1 (360 mg/kg) were given alone or combined i.p. 60 and p.o. 30 min, respectively, before FST. The effect of single and repeated administration (once a day for 3 consecutive days) of HC1 (360 mg/kg) on Na⁺, K⁺ ATPase activity was evaluated ex vivo in the cerebral cortex and hippocampus of mice subjected or not to FST. RESULTS: HC1 reduced the immobility time (103.15 ± 18.67 s), when compared to the control group (183.6 ± 9.51 s). This effect was prevented by veratrine (151.75 ± 22.19 s). Mice repeatedly treated with HC1 presented a significant increase in Na⁺, K⁺ ATPase activity, both in cerebral cortex (46 ± 2.41 nmol Pi/min·mg protein) and hippocampus (49.83 ± 2.31 nmol Pi/min·mg protein), in relation to the respective controls (30 ± 2.66 and 29.83 ± 2.31 nmol Pi/min·mg protein respectively). DISCUSSION AND CONCLUSION: The HC1 antidepressant-like effect on FST might be related to its capacity to inhibit Na⁺ influx. HC1 increases hippocampal and cortical Na⁺, K⁺ ATPase activities possibly through long-term regulatory mechanisms.

Acylphloroglucinols from Elaphoglossum crassipes: antidepressant-like activity of crassipin A.

Nine new terpenylated acylphloroglucinols, crassipins A-I, were isolated from the rhizomes and roots of the fern Elaphoglossum crassipes, and their structures were elucidated by analysis of spectroscopic data and chemical derivatization. The absolute configurations of some of the compounds were established by CD and VCD in combination with a quantum mechanical method. Crassipin A (1), the major acylphloroglucinol of the Et(2)O extract of E. crassipes, as well as its peracetylated derivative (8), displayed antidepressant-like activity in a mouse forced-swimming test when administered orally at a dose of 15 mg/kg.

In vitro effect of valepotriates isolated from Valeriana glechomifolia on rat P-type ATPases.

Valepotriates are iridoids found in variable amounts in Valerianaceae and might be among the bioactive compounds which confer anxiolytic properties to the Valeriana species. On the other hand, unspecific cytotoxicity has also been described. Presently, however, no particular molecular target has been defined for these compounds. Here we studied the effect of valtrate, acevaltrate, and 1- ß-acevaltrate isolated from Valeriana glechomifolia on the enzymatic activity of rat P-type ATPases. Valepotriates did not affect rat skeletal muscle sarco/endoplasmic reticulum Ca²âº-ATPase (SERCA) activity at the highest concentration used (100 µM). In contrast, the same concentration inhibited roughly half of the total H⁺/K⁺-ATPase activity from rat gastric epithelium (valtrate 54.6 ± 3.2 %, acevaltrate 60.7 ± 7.3 %, 1- ß-acevaltrate 50.2 ± 3.1 %; mean ± SEM, n = 3-5). Finally, these substances showed the highest inhibitory potency toward Na⁺/K⁺-ATPase, and the inhibition curves obtained provided a similar IC50 (in µM) for rat kidney α1 isoform (valtrate 21.2, acevaltrate 22.8, 1- ß-acevaltrate 24.4) and brain hemispheres α2/ α3 isoforms (valtrate 19.4, acevaltrate 42.3, 1- ß-acevaltrate 38.3). Our results suggest that P-type ATPases are differentially inhibited by valepotriates and that Na⁺/K⁺-ATPase might be one of their molecular targets in vivo.

Intermittent repeated stress but not ketamine changes mice response to antidepressants.

Discovery of the rapid antidepressant effect of ketamine has been considered one of the most important advances in major depressive disorder treatment. Several studies report a significant benefit to patients that lasts up to 19 days after treatment. However, concerns arise from the long-term use of ketamine, thus a safe and effective strategy for maintaining its antidepressant effect is still necessary. To this end, our work assessed the effects of imipramine and fluoxetine after repeated ketamine treatment in male mice. Ketamine (30 mg/kg/day for 14 days) induced an anti-immobility effect in the forced swimming (FS) paradigm, detected 1 and 3 days after treatment. Seven days after the last ketamine injection, mice received imipramine (20 mg/kg) or fluoxetine (30 mg/kg). Imipramine and fluoxetine did not change mice's immobility time, regardless of the pre-treatment (saline or ketamine). Since both drugs' anti-immobility effect was demonstrated in the classical FS test, we can assume that repeated exposure to intermittent stress inhibited the antidepressant drugs' anti-immobility effects. Moreover, pre-exposure to ketamine did not counteract stress-induced changes in mice response to antidepressants. Since exposure to forced swim and i.p. injections are stressful to rodents, each stressor's contribution to the blunted response to antidepressants was investigated. Our data demonstrated that both stressors (FS and i.p. injections) influenced the reported effect. In summary, our results showed that exposure to intermittent repeated stress inhibited the anti-immobility effect of imipramine and fluoxetine in mice and corroborated findings demonstrating that exposure to stress can blunt patients' response to antidepressants.

Design of new dopamine D2 receptor ligands: biosynthesis and pharmacological evaluation of the hydroxylated metabolite of LASSBio-581.

LASSBio-581 is a N-phenylpiperazine derivative designed for the treatment of schizophrenia. In this study, four strains of filamentous fungi were screened for their capabilities to biotransform LASSBio-581. Cunninghamella echinulata ATCC 9244 was chosen to scale up the biosynthesis of the p-hydroxylated metabolite of LASSBio-581. The chemical structure of the metabolite was confirmed by NMR, LC-MS and X-ray crystallography. Binding studies performed on brain homogenate indicated that the p-hydroxylated metabolite can be considered more selective for dopamine receptors than LASSBio-581, and, therefore, can be used to design new selective dopamine inhibitors.

Searching for multi-target antipsychotics: Discovery of orally active heterocyclic N-phenylpiperazine ligands of D2-like and 5-HT1A receptors.

We described herein the design, synthesis, and pharmacological evaluation of N-phenylpiperazine heterocyclic derivatives as multi-target compounds potentially useful for the treatment of schizophrenia. The isosteric replacement of the heterocyclic ring at the biaryl motif generating pyrazole, 1,2,3-triazole, and 2-methylimidazole[1,2-a]pyridine derivatives resulted in 21 analogues with different substitutions at the para-biaryl and para-phenylpiperazine positions. Among the compounds prepared, 4 (LASSBio-579) and 10 (LASSBio-664) exhibited an adequate binding profile and a potential for schizophrenia positive symptoms treatment without cataleptogenic effects. Structural features of this molecular scaffold are discussed regarding binding affinity and selectivity for D(2)-like, 5-HT(1A), and 5-HT(2A) receptors.

Serotonergic neurotransmission mediates hypothermia induced by the N-phenylpiperazine antipsychotic prototypes LASSBio-579 and LASSBio-581.

Previous studies have demonstrated that LASSBio-579 and LASSBio-581, two N-phenylpiperazine derivatives designed for the treatment of schizophrenia, are presynaptic dopamine D(2) receptor agonists that induce a hypothermic effect in mice that is not mediated by dopamine receptor activation. The aim of the present study was to investigate possible serotonergic mechanisms underlying hypothermia induced by LASSBio-579 and LASSBio-581 in CF1 mice. The reduction in core temperature was dose-dependent (15-60 mg/kg, i.p.) and occurred by the oral route (30 mg/kg). Pretreatment with haloperidol (4 mg/kg, i.p.) resulted in a synergistic hypothermic effect. Pretreatment with (+/-)DOI (0.25 mg/kg, i.p.), a serotonin 5-HT(2A/C) receptor agonist, reduced the hypothermic effect induced by LASSBio-579 and LASSBio-581 at 15 and 30 mg/kg, i.p. In contrast, (+/-)DOI enhanced the hypothermia induced by both compounds at 60 mg/kg, i.p. The serotonin 5-HT1A antagonist WAY 100635 (0.05 mg/kg, s.c.) abolished the hypothermia induced by LASSBio-579 and diminished the hypothermia induced by LASSBio-581. Pretreatment with LASSBio579 (30 and 60 mg/kg, i.p.) and LASSBio-581 (60 mg/kg, i.p.) reduced the number of head-twitches induced by (+/-)DOI (2.5 mg/kg, i.p.). The ear-scratch response induced by (+/-)DOI was inhibited by both LASSBio-579 and LASSBio-581 at 60 mg/kg, i.p. These results indicate that LASSBio-579 and LASSBio-581 have mechanisms of action through the serotonergic neurotransmitter system.

Comparisons between anxiety tests for selection of anxious and non anxious mice.

Male Swiss albinos mice were submitted to two behavioural tests intended to determine their anxiety level: the elevated plus-maze test as well as the black and white compartments test. In addition they were submitted to the hole-board test. It was observed: (i) that the correlation between scores in the two first tests was weak, suggesting that they explore different components of anxiety; (ii) that the score on the latter test was better correlated with the response in the elevated plus-maze test than in the black and white compartments test. From these data three groups of animals were constituted, considered, respectively, as anxious, non anxious and intermediates. It was observed that both horizontal and vertical locomotion in an unfamiliar environment differed between groups, with higher activity in non anxious than in anxious. In the hole-board test, only animals classified as anxious displayed an obvious response to the anxiolytic drug diazepam (0.5mg/kg). Finally in the forced-swimming test, the three groups demonstrated a similar immobility time, suggesting that the operated segregation was not depending on a helpless component. It is proposed that the selection of mice from a combination of either elevated plus-maze and black and white compartments tests or a combination of hole-board test and black and white compartments test, allows to distinguish high or low anxiety animals among a population of mice.

Hypericum caprifoliatum (Guttiferae) Cham. & Schltdl.: a species native to South Brazil with antidepressant-like activity.

In this work, previously published and unpublished results on biological activity of Hypericum caprifoliatum, a native species to South Brazil, are presented. Lipophilic extracts obtained from this species showed an antidepressant-like activity in mice and rat forced swimming test. Results from in vivo experiments suggest an effect on the dopaminergic transmission. Besides that, in vitro experiments demonstrated that the extract and its main component (a phloroglucinol derivative) inhibit monoamine uptake in a concentration-dependent manner, more potently to dopamine, but this effect is not related to direct binding at the uptake sites. It was also observed that a 3-day treatment with lipophilic extract prevents stress-induced corticosterone rise in mice frontal cortex but not in plasma. The lipophilic and methanolic H. caprifoliatum extracts also demonstrated antinociceptive effect, which seems to be indirectly mediated by the opioid system. These results indicate that H. caprifoliatum presents a promising antidepressant-like effect in rodents which seems to be related to a mechanism different from that of other classes of antidepressants.

Dimeric acylphloroglucinols from Hypericum austrobrasiliense exhibiting antinociceptive activity in mice.

Three dimeric acylphloroglucinols, austrobrasilol A, austrobrasilol B and isoaustrobrasilol B were isolated from the flowers of Hypericum austrobrasiliense (Hypericaceae, section Trigynobrathys). Their structures were elucidated using mass spectrometry and NMR experiments (1D and 2D), and by comparison with previously reported data for other dimeric acylphloroglucinols isolated from Hypericum and Elaphoglossum genera. The three compounds were orally administered in mice at equimolar doses to uliginosin B (15mg/kg, p.o.) displaying antinociceptive activity in the hot-plate test. The compounds did not induce motor impairment in the rotarod apparatus.

Synergistic interaction between diene valepotriates from Valeriana glechomifolia†Meyer (Valerianaceae) and classical antidepressants: an isobolographic analysis.

OBJECTIVES: Combinations of different classes of antidepressants (including herbal adjuvants) have been used as an alternative means of achieving better results in the treatment of depressed patients. However, studies characterizing the interactions between herbal adjuvants and antidepressants are lacking. This study is the first to investigate the interaction between diene valepotriates (VAL) from Valeriana glechomifolia, a species with antidepressant-like effects, and imipramine (IMI), desipramine (DESI) and bupropion (BUP). The interactions were assessed via isobolographic analyses, which represent a tool for evaluating interactions between drugs. METHODS: The interaction between VAL and each antidepressant was evaluated in mice given concurrent oral administration of each drug with fixed ED50 ratios and subjected to a forced swimming test (FST). Spontaneous locomotion was measured in the open field test. KEY FINDINGS: The drug combinations produced a dose-dependent anti-immobility effect in the FST without altering mouse locomotor activity. Isobolographic analysis revealed that VAL resulted in synergistic interactions in combination with each of the antidepressants tested. CONCLUSION: The synergistic interactions between VAL and IMI, DESI and BUP highlight the potential for VAL to serve as adjuvants to antidepressant drugs and suggest that VAL does not directly target the same sites on neuronal transporters as the antidepressants.

Mucoadhesive Amphiphilic Methacrylic Copolymer-Functionalized Poly(ε-caprolactone) Nanocapsules for Nose-to-Brain Delivery of Olanzapine.

Nose-to-brain drug delivery has been proposed to overcome the low absorption of drugs in central nervous system due to the absence of brain-blood barrier in the olfactory nerve pathway. However, the presence of a mucus layer and quick clearance limit the use of this route. Herein, amphiphilic methacrylic copolymer-functionalized poly(ε-caprolactone) nanocapsules were proposed as a mucoadhesive system to deliver olanzapine after intranasal administration. In vitro evaluations showed that these nanocapsules were able to interact with mucin (up to 17% of increment in particle size and 30% of reduction of particle concentration) and nasal mucosa (2-fold higher force for detaching), as well as to increase the retention of olanzapine (about 40%) on the nasal mucosa after continuous wash. The olanzapine-loaded amphiphilic methacrylic copolymer-functionalized PCL nanocapsules enhanced the amount of drug in the brain of rats (1.5-fold higher compared to the drug solution). In accordance with this finding, this formulation improved the prepulse inhibition impairment induced by apomorphine, which is considered as an operational measure of pre-attentive sensorimotor gating impairment present in schizophrenia. Besides, nanoencapsulated olanzapine did not affect the nasal mucosa integrity after repeated doses. These data evidenced that the designed nanocapsules are a promising mucoadhesive system for nose-to-brain delivery of drugs.

Uliginosin B, a natural phloroglucinol derivative, presents a multimediated antinociceptive effect in mice.

OBJECTIVE: Investigate the involvement of monoaminergic and glutamatergic systems on the antinociceptive and ataxic effects of uliginosin B, which we have already demonstrated to be a promising molecular scaffold to develop new analgesic drugs. METHODS: Uliginosin B was obtained from hexane extract of aerial parts of Hypericum polyanthemum by chromatographic methods. Uliginosin B antinociceptive and motor coordination effects were evaluated in mice by using hot-plate (15 and 90 mg/kg, i.p.) and rotarod (90 mg/kg, i.p.) tests, respectively. The mechanism of action was investigated through pretreatments with prazosin 1 mg/kg intraperitoneal (α1 receptor antagonist), yohimbine 5 mg/kg intraperitoneal (α2 receptor antagonist), pCPA 300 mg/kg intraperitoneal (serotonin synthesis inhibitor) and MK-801 0.25 mg/kg intraperitoneal (N-methyl-D-aspartic acid receptor antagonist). KEY FINDINGS: The antinociceptive effect of uliginosin B (15 and 90 mg/kg, i.p.) was reduced significantly by pCPA and MK-801. Prazosin and yohimbine improved the antinociceptive effect of the highest dose (90 mg/kg, i.p.) of uliginosin B only. The ataxic effect of uliginosin B (90 mg/kg, i.p.) was completely prevented by pretreatment with pCPA or MK-801, but it was unaffected by pretreatment with prazosin or yohimbine. CONCLUSION: These data confirm the contribution of monoaminergic neurotransmission as well as provide the first evidence of glutamatergic neurotransmission contribution to the uliginosin B effects.

Determination of pharmacological interactions of uliginosin B, a natural phloroglucinol derivative, with amitriptyline, clonidine and morphine by isobolographic analysis.

Uliginosin B is a natural phloroglucinol derivative, obtained from Hypericum species native to South America. Previous studies have shown that uliginosin B presents antidepressant-like and antinociceptive effects. Although its mechanism of action is still not completely elucidated, it is known that it involves the activation of monoaminergic neurotransmission. The aim of the current study was to further investigate the antinociceptive mechanism of action of uliginosin B by combining it with different drugs used for treating pain in clinical practice. The intraperitoneal administration of uliginosin B, morphine, amitriptyline and clonidine, alone or in mixture, produced a dose-dependent antinociceptive effect in the hot-plate assay in mice. The effect of the mixtures of drugs was studied using an adapted isobologram analysis at the effect level of 50% of the maximal effect observed. The analysis showed that the interactions between uliginosin B and morphine was synergistic, while the interactions between uliginosin B and amitriptyline or clonidine were additive. These findings point to uliginosin B as a potential adjuvant for pain pharmacotherapy, especially for opioid analgesia.