Anticonvulsant and anxiolytic-like potential of the essential oil from the Ocimum basilicum Linn leaves and its major constituent estragole on adult zebrafish (Danio rerio).

The Ocimum species present active compounds with the potential to develop drugs for treating chronic disease conditions, such as anxiety and seizures. The present study aims to investigate the anticonvulsant and anxiolytic-like effect of the essential oil from O. basilicum Linn (OEFOb) leaves and its major constituent estragole (ES) in vivo on adult zebrafish (aZF) and in silico. The aZF were treated with OEFOb or ES or vehicle and submitted to the tests of toxicity, open-field, anxiety, and convulsion and validated the interactions of the estragole on the involvement of GABAergic and serotonergic receptors by molecular docking assay. The results showed that the oral administration of OEFOb and ES did not have a toxic effect on the aZF and showed anxiolytic-like effects with the involvement of GABAA, 5-HT1, 5-HT2A/2C and 5-HT3A/3B as well on anxiety induced by alcohol withdrawal. The OEFOb and ES showed anticonvulsant potential attenuating the seizures induced by pentylenetetrazole (PTZ) by modulation of the GABAA system. Both anxiolytic and anticonvulsant effects were corroborated by the potential of the interaction of ES by in silico assay. These study samples demonstrate the pharmacological evidence and potential for using these compounds to develop new anxiolytic and anticonvulsant drugs.

Combretum lanceolatum extract reverses anxiety and seizure behavior in adult zebrafish through GABAergic neurotransmission: an in vivo and in silico study.

Combretaceae are reported in the literature for presenting neuroprotective and anxiolytic effects in animal models. Combretum lanceolatum Pohl. has few scientific reports on its pharmacological effects. The aim of this study was to evaluate the anxiolytic and anticonvulsant effects of the ethanol extract from the leaves of C. lanceolatum Pohl. (EtFoCl) and its possible mechanism of GABAergic action in adult zebrafish. EtFoCl was subjected to determination of the total phenol concentration, identification of phytochemical flavonoids by HPLC and in vitro antioxidant activity test, open field test and 96-hour acute toxicity in zebrafish. Anxiolytic doses were tested for pentylenetetrazole-induced seizures in adult zebrafish. To study the mechanisms of action, molecular docking simulations were performed between the main phytochemicals and the GABAA receptor (anxiolytic activity) and carbonic anhydrase II (anticonvulsant). The non-toxic doses that caused motor impairment were assessed in acute and chronic anxiety using the light and dark test. EtFoCl had altered the animals' locomotion, presenting an effect similar to the anxiolytic and anticonvulsant. These effects were prevented with flumazenil (GABAA antagonist). The phytochemicals homoorientin and quercetin-3-O-galactoside coupling in a region close to that of the inhibitor diazepam (GABAA receptor). Regarding the anticonvulsant mechanism, Homoorientina and Isovitexina were identified as the most favorable for the complex form with the carbonic anhydrase enzyme. C. lanceolatum has pharmacological potential for the treatment of acute and chronic anxiety and seizures, which can be partially explained by an interaction with the GABAA receptor.Communicated by Ramaswamy H. Sarma.

Antinociceptive Effect of the Essential Oil of Schinus terebinthifolius (female) Leaves on Adult Zebrafish (Danio rerio).

Schinus terebinthifolius Raddi (Anacardiaceae) is popularly known in Brazil as aroeira-da-praia and has pharmacological use as an astringent, antidiarrheal, anti-inflammatory, depurative, diuretic, and antifebrile agent. Although the neuropathic antinociceptive potential of S. terebinthifolius fruits has already been investigated, this study is the first one to analyze the acute antinociceptive effect of the essential oil of S. terebinthifolius (female) leaves (EOFSt) on adult zebrafish. EOFSt was submitted to antioxidant activity evaluation by two methods (ferrous ion-chelating capacity [FIC] and ß-carotene). The animals (n = 6/group) were treated orally (20 µL) with EOFSt (0.1, 0.5, or 1.0 mg/mL) or vehicle (0.9% sodium chloride [NaCl]; 20 µL), and submitted to nociception (formalin, cinnamaldehyde, capsaicin, glutamate, acidic saline, and hypertonic saline). Possible neuromodulation mechanisms, as well motor alterations and toxicity were also evaluated. In the FIC assay, EOFSt showed ferrous ion-chelating capacity in ∼40% to 90%. Regarding the ß-carotene bleaching assay, EOFSt showed inhibition in a 58% to 80% range. Oral administration of EOFSt showed no acute toxicity and did not alter the locomotor system of aZF, and reduced the nociceptive behavior in all tested models. These effects of EOFSt were significantly similar to those of morphine, used as a positive control. The antinociceptive effect of EOFSt was inhibited by naloxone, L-NAME, ketamine, camphor, ruthenium red, and amiloride. The antinociceptive effect of the EOFSt cornea was inhibited by capsazepine. EOFSt has the pharmacological potential for acute pain treatment and this effect is modulated by the opioid system, NMDA receptors, and transient receptor potential ankyrin 1 (TRPA1), transient receptor potential vanilloid 1 (TRPV1), and acid-sensing ion channels. The EOFSt also has the pharmacological potential for corneal pain treatment and this effect is modulated by the TRPV1 channel.

Anxiolytic-like effect of chalcone N-{(4'-[(E)-3-(4-fluorophenyl)-1-(phenyl) prop-2-en-1-one]} acetamide on adult zebrafish (Danio rerio): Involvement of the GABAergic system.

Benzodiazepines are the standard drugs for the treatment of anxiety, but their undesirable side effects make it necessary to develop new anxiolytic drugs. The objective of this study was to evaluate the possible anxiolytic-simile effect of synthetic chalcone N-{(4'-[(E)-3-(4-fluorophenyl)-1-(phenyl) prop-2-en-1-one]} acetamide (PAAPFBA) on adult zebrafish (Danio rerio). PAAPFBA was synthesized with an 88.21% yield and its chemical structure was determined by 1H and 13C NMR. Initially, animals (n = 6/group) were treated (4 or 12 or 40 mg/kg, intraperitoneal) with PAAPFBA and were submitted to acute toxicity and open field tests. Then, other groups (n = 6/each) received PAAPFBA for the analysis of its effect on the Light & Dark Test. The participation of the GABAergic system was also assessed using the GABAA antagonist flumazenil. Molecular docking was performed using the GABAA receptor. The effect of PAAPFBA on anxiety induced by alcohol withdrawal was analyzed. PAAPFBA was non-toxic, reduced the locomotor activity, and showed an anxiolytic-like effect in both models. This effect was reduced by pre-treatment with the flumazenil. In agreement with in vivo studies, molecular docking indicated an interaction between chalcone and the GABAA receptor. The results suggest that PAAPFBA is an anxiolytic agent mediated via the GABAergic system.

Molecular mechanism underlying orofacial antinociceptive activity of Vanillosmopsis arborea Baker (Asteraceae) essential oil complexed with ß-cyclodextrin.

BACKGROUND: Vanillosmopsis arborea Baker has recognized economic value owing to the high content of (-)-α-bisabolol (BISA) in the essential oil of its stem (EOVA). The antinociceptive effect of EVOA has already been demonstrated, and ß-cyclodextrin (ßCD) is known to improve the analgesic effect of various substances. PURPOSE: Thus, we aimed to evaluate the orofacial antinociceptive effect of a complex containing EOVA-ßCD in rodents. METHODS: EOVA was obtained by simple hydrodistillation, and the essential oil was complexed with ßCD. The animals (n = 6/group) were treated orally with EOVA-ßCD (10 or 50 mg/kg), or vehicle (control), and subjected to cutaneous orofacial nociception (formalin, capsaicin, acidic saline or glutamate), corneal (hypertonic saline) or temporomandibular (formalin) tests. The expression of FOS protein was analyzed in the spinal cord. Molecular docking was performed using the 5-HT3 and M2 receptors and BISA. RESULTS: The oral administration of EOVA-ßCD reduced nociceptive behaviour. Moreover, EOVA-ßCD decreased FOS expression. The molecular docking study indicates that BISA interacts with 5-HT3 and M2 receptors, indicating the potential mechanism of action of the tested compound. CONCLUSIONS: Our results indicate that EOVA-ßCD possesses orofacial antinociceptive effect, indicating that this complex can be used in analgesic drug development.

Oleanolic acid promotes orofacial antinociception in adult zebrafish (Danio rerio) through TRPV1 receptors.

This study aimed to evaluate the antinociceptive effect of oleanolic acid using adult zebrafish models of orofacial pain. Acute nociception was induced by formalin, capsaicin, cinnamaldehyde, menthol, acidified saline or glutamate (cutaneous modes) and hypertonic saline (corneal model). In another set of experiments, animals were pre-treated with naloxone, L-NAME, methylene blue, ketamine, camphor, HC-030031, mefenamic acid, ruthenium red or amiloride to investigate the mechanism of antinociception. The involvement of central afferent C-fibers was also investigated. A molecular docking was performed using the TRPV1 channel. Motor activity was evaluated with the open field test. Pre-treatment with oleanolic acid significantly reduced nociceptive behavior associated with acute pain. Antinociception was effectively inhibited by ruthenium red and capsaicin-induced desensitization. Presence of trpv1 was confirmed by RT-PCR in cerebral tissue of zebrafish. In line with in vivo experiments, docking studies indicated that oleanolic acid may interact with TRPV1. Results confirm the potential pharmacological relevance of oleanolic acid as an inhibitor of orofacial nociception mediated by TRPV1.

Antinociceptive activity of ethanolic extract of Azadirachta indica A. Juss (Neem, Meliaceae) fruit through opioid, glutamatergic and acid-sensitive ion pathways in adult zebrafish (Danio rerio).

Neem fruit (Azadirachta indica A. Juss.) are popularly used to treat infections, diarrhea, fever, bronchitis, skin diseases, infected burns and hypertension. Although the antinociceptive and anti-inflammatory potential of A. indica has already been investigated in experimental models of pain and inflammation in mice, the current research is the first to report the evaluation of the capacity of A. indica fruit ethanolic extract (EtFrNeem) in acute pain attenuation using the adult zebrafish (Danio rerio) as an alternative model to the use in rodents. EtFrNeem was submitted to antioxidant action, preliminary chemical prospecting, FT-IR and determination of phenol and flavonoid content tests. Subsequently, EtFrNeem was tested for acute nociception and abdominal inflammation, locomotor activity, and acute toxicity in adult zebrafish. Possible neuromodulation mechanisms were also evaluated. EtFrNeem showed low antioxidant activity, but was shown to be rich in flavonoids. EtFrNeem showed no anti-inflammatory action, did not alter the locomotor system, and it was not toxic. However, EtFrNeem significantly reduced the nociceptive behavior induced by formalin, glutamate and acidic saline, when compared to the control group. These effects of EtFrNeem were significantly similar to those of morphine, used as a positive control. The antinociceptive effect of EtFrNeem was inhibited by naloxone, ketamine and amiloride. EtFrNeem has the pharmacological potential for acute pain treatment and this effect is modulated by the opioid system, NMDA receptors and ASICs channels. These results lead us to studies of isolation and characterization of EtFrNeem bioactive principles, using adult zebrafish as an experimental model.

Orofacial antinociceptive effect of Mimosa tenuiflora (Willd.) Poiret.

Mimosa tenuiflora (Willd.) Poiret, popularly known in Brazil as "jurema-preta" is widely used against bronchitis, fever, headache and inflammation. Its antioxidant, anti-inflammatory and antinociceptive potential has already been reported. To assess the orofacial antinociceptive effect of M. tenuiflora, ethanolic extracts of M. tenuiflora (leaves, twigs, barks and roots) were submitted to in vitro tests of antioxidant activity. The extract with the highest antioxidant potential was partitioned and subjected to preliminary chemical prospecting, GC-MS, measurement of phenolic content and cytotoxicity tests of the fraction with the highest antioxidant activity. The nontoxic fraction with the highest antioxidant activity (FATEM) was subjected to tests of acute and chronic orofacial nociception and locomotor activity. The possible mechanisms of neuromodulation were also assessed. The EtOAc fraction, obtained from the ethanolic extract of M. tenuiflora barks, was the one with the highest antioxidant potential and nontoxic (FATEM), and Benzyloxyamine was the major constituent (34.27%). FATEM did not alter the locomotor system of mice and reduced significantly the orofacial nociceptive behavior induced by formalin, glutamate, capsaicin, cinnamaldehyde or acidic saline compared to the control group. FATEM also inhibited formalin- or mustard oil-induced temporomandibular nociception. In addition, it also reduced mustard oil-induced orofacial muscle nociception. However, FATEM did not alter hypertonic saline-induced corneal nociception. Neuropathic nociception was reversed by treatment with FATEM. The antinociceptive effect of FATEM was inhibited by naloxone, L-NAME and glibenclamide. FATEM has pharmacological potential for the treatment of acute and neuropathic orofacial pain and this effect is modulated by the opioid system, nitric oxide and ATP-sensitive potassium channels. These results lead us to studies of isolation and characterization of bioactive principles.