Quantifying drug-drug interactions in pharmaco-EEG

Antinociceptive and gastroprotective activities of Bocconia arborea S. Watson and its bioactive metabolite dihydrosanguinarine in murine models

ETHNOPHARMACOLOGICAL RELEVANCE

Bocconia arborea S. Watson (Papaveraceae) is known as "palo llora sangre" and is used in Mexican traditional medicine for the treatment of infections, it is also used as anxiolytic, analgesic, and antidiabetic, among others.

AIM OF THE STUDY

to evaluate the antinociceptive and gastroprotective activities of extracts from B. arborea and dihydrosanguinarine (DHS) in murine models.

MATERIALS AND METHODS

Organic extracts [hexane (HEX), dichloromethane (DCM) and methanol (MeOH)] were obtained by maceration. DHS was isolated and purified from HEX and DCM by precipitation and chromatographic column, respectively. Organic extracts and DHS were evaluated to determine their antinociceptive effect using formalin test in murine model. Also, the ambulatory effect of the HEX and DHS was determined in Open field test. The possible mechanism of action of DHS was explored in the presence of naltrexone (NTX, 1 mg/kg, i.p.), and picrotoxin (PTX, 1 mg/kg, i.p.). Gastric damage as possible adverse effect or gastroprotection were also investigated. Whereas DHS acute toxicological study was done, and 100 mg/kg of DHS was examined by electroencephalographic (EEG) analysis to discard neurotoxic effects.

RESULTS

The B. arborea extracts significantly showed effects in both neurogenic and inflammatory phases of the formalin test, where the HEX extract reached the major antinociceptive effect. A significant and dose-response (10, 30, and 100 mg/kg) antinociceptive activity was observed with the HEX (ED₅₀ = 69 mg/kg) and DHS (ED₅₀ = 85 mg/kg) resembling the effect of the reference analgesic drug tramadol (30 mg/kg). The significant effect of DHS was inhibited in the presence of NTX and PTX. Neither the extracts or DHS produced sedative effects or gastric damage per se at antinociceptive doses. The EEG analysis demonstrated central depressant activity but not sedative or neurotoxic effects at the highest antinociceptive dosage tested, and LD₅₀ is higher than 2000 mg/kg.

CONCLUSIONS

HEX, DCM, and MeOH extracts showed significant antinociceptive activity, and DHS was identified as one of bioactive compounds without producing sedative, neurotoxic or gastric damage effects, as possible adverse effects reported for analgesic drugs. A role of opioid and GABA_A neurotransmission appears to be involved as mechanisms of action of DHS, suggesting its potential for pain therapy and reinforcing the traditional use of B. arborea.

Tabernaemontana arborea and ibogaine induce paroxysmal EEG activity in freely moving mice: involvement of serotonin 5-HT1A receptors

Several Apocynaceae species, most notably Tabernanthe iboga, Voacanga africana and many Tabernaemontana species, produce ibogan-type alkaloids. Although a large amount of information exists about the Tabernaemontana genus, knowledge concerning chemistry and biological activity remains lacking for several species, especially related to their effects on the central nervous system (CNS). The aim of this study was to evaluate the effect of Tabernaemontana arborea Rose ex J.D.Sm. (T. arborea) hydroalcoholic extract (30, 56.2 and 100 mg/kg, i.p.) and two of its main alkaloids (ibogaine and voacangine, 30 mg/kg, i.p.) on electroencephalographic (EEG) activity alone and in the presence of the chemical convulsant agent pentylenetetrazole (PTZ, 85 mg/kg, i.p.) in mice. EEG spectral power analysis showed that T. arborea extract (56.2 and 100 mg/kg) and ibogaine (30 mg/kg, i.p.) promoted a significant increase in the relative power of the delta band and a significant reduction in alpha band values, denoting a CNS depressant effect. Voacangine (30 mg/kg, i.p.) provoked an EEG flattening pattern. The PTZ-induced seizures were not modified in the presence of T. arborea, ibogaine, or voacangine. However, sudden death was observed in mice treated with T. arborea extract at 100 mg/kg, i.p., combined with PTZ. Because T. arborea extract (100 mg/kg, i.p.) and ibogaine (30 mg/kg, i.p.), but not voacangine (30 mg/kg, i.p.), induced paroxysmal activity in the EEG, both were explored in the presence of a serotonin 5-HT_1A receptor antagonist (WAY100635, 1 mg/kg, i.p.). The antagonist abolished the paroxysmal activity provoked by T. arborea (100 mg/kg, i.p.) but not that observed with ibogaine, corroborating the participation of serotonin neurotransmission in the T. arborea effects. In conclusion, high doses of the T. arborea extract induced abnormal EEG activity due in part to the presence of ibogaine and involving serotonin 5-HT_1A receptor participation. Nevertheless, other possible constituents and mechanisms might participate in this complex excitatory activity that would be interesting to explore in future studies.

Pharmacological and toxicological effects of Ruta chalepensis L. on experimentally induced seizures and electroencephalographic spectral power in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Ruta chalepensis L. (Rutaceae) is used in traditional medicine to treat a wide variety of disorders such as rheumatism, fever, mental disorders, dropsy, neuralgia, menstrual problems, anxiety, and epilepsy.

AIM OF THE STUDY

To evaluate and compare the anticonvulsant properties of an aqueous extract and ethyl acetate (AcOEt) fraction of R. chalepensis on pentylenetetrazole (PTZ)-induced seizures and maximal electroshock (MES) test in mice, by analyzing behavior and electroencephalogram (EEG), as well as GABA_A receptors involvement.

METHODS

The effect of an acute administration of different dosage of the aqueous extract (300 or 500 mg/kg) or AcOEt fraction (100, 300, 500 or 1000 mg/kg) of R. chalepensis was explored on two different models of acute seizure induction in mice, the PTZ and maximal electroshock (MES) tests. Behavioral and electrographic effects were quantified. Additionally, the possible involvement of the GABA_A receptors was explored in the presence of picrotoxin (a non-competitive antagonist of the GABA_A receptor).

RESULTS

AcOEt fraction of R. chalepensis was more efficient than aqueous extract to reduce the incidence of tonic-clonic seizures and mortality in a significant and dose-dependent manner in both the PTZ and MES tests. This anticonvulsant effect was not abolished in the presence of picrotoxin. The EEG spectral power analysis revealed that aqueous extract decreased alpha and beta power, while AcOEt fraction decreased alpha and gamma power confirming previous findings of its depressant effect in the central nervous system. It is important to mention that the highest dosage of the AcOEt (1000 mg/kg) produced a severe suppression or isoelectric EEG activity (EEG flattening), recognized as a comatose state, suggesting a neurotoxic effect at this dosage.

CONCLUSION

Our data reinforce that depressant and anticonvulsant effects of R. chalepensis depend in part on the presence of constituents from medium polarity. We also found that anticonvulsant effect is not mediated by GABA_A receptors. In addition, cautious is emphasized when high doses of this natural product are used in traditional medicine since it might produce neurotoxic effects.

Anticonvulsant effect of Marsilea quadrifolia Linn. on pentylenetetrazole induced seizure: a behavioral and EEG study in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Marsilea quadrifolia Linn (MQ) extract has been used traditionally as sedative and antiepileptic drug in India.

AIM OF THIS STUDY

To investigate the anticonvulsive potential of MQ extracts by using behavior and electroencephalographic (EEG) analysis on pentylenetetrazole (PTZ) induced seizure model in rats.

MATERIALS AND METHODS

For anticonvulsant effect, 60minutes after administration of MQ, behavior and EEG were analyzed during PTZ (60mg/kg) induced seizures. Changes of EEG power, latency of onset of seizure, seizure severity score, and duration of epileptic seizure were determined.

RESULTS

Both the water and ethanol extract of MQ increased the latency of seizure but also decreased duration of epileptic seizure and seizure severity score. This reduction of seizure severity was also observed in EEG recording and EEG power analysis. The effectiveness of MQ ethanol extract is better than MQ water extract.

CONCLUSION

Both water and ethanol extract of MQ were effective in reducing the severity of behavioral and EEG seizures induced by PTZ in rats. This study justifies the traditional use of this plant in epilepsy.

Influence of ocular filtering in EEG data on the assessment of drug-induced effects on the brain

Ocular artifacts in EEG signals affect the interpretation of clinical study results. The aim of this study was to assess the influence of automatic ocular filtering procedures in the conclusions drawn from a pharmaco-EEG trial. Regression analysis, gold standard, and blind source separation (BSS), Second Order Blind Identification algorithm, ocular filtering procedures were compared using time, frequency, topographic and tomographic brain mapping approaches and pharmacokinetic-pharmacodynamic (PK-PD) relationships. Data consisted of EEGs obtained from 20 volunteers who received single oral doses of haloperidol 3 mg, risperidone 1 mg, olanzapine 5 mg and placebo in a randomized cross-over double-blind design. Although the BSS-based technique preserved brain activity more than regression analysis in anterior leads, in general, topographic significance probability maps globally showed similar results with both methods for most spectral variables. However, different results were obtained when using whole multi-channel information for studying drug effects in the brain: (i) higher correlations between PK and PD time courses showing that BSS allowed estimation of spectral variables more accurately related to drug effects and (ii) larger and more symmetric drug related tomographic LORETA maps showing that BSS led to results that were more neurophysiopharmacologically sound. Definitely, the BSS-based procedure is an effective and efficient preprocessing method to remove ocular artifacts from EEG data. The selection of the ocular filtering procedure could determine different results whose impact depends on the evaluating tool applied to analyze the pharmaco-EEG data.