E.T. Venâncio

Anxiolytic-like effect of Carvacrol (5-isopropyl-2-methylphenol) in mice: involvement with GABAergic transmission.

Carvacrol (5‐isopropyl‐2‐methylphenol) is a monoterpenic phenol present in the essencial oil of many plants. It is the major component of the essential oil fraction of oregano and thyme. This work presents the behavioral effects of carvacrol in animal models of elevated plus maze (EPM), open field, Rotarod and barbiturate‐induced sleeping time tests in mice. Carvacrol (CVC) was administered orally, in male mice, at single doses of 12.5; 25 and 50 mg/kg while diazepam 1 or 2 mg/kg was used as standard drug and flumazenil (2.5 mg/kg) was used to elucidate the possible anxiolytic mechanism of CVC on the plus maze test. The results showed that CVC, at three doses, had no effect on the spontaneous motor activity in the Rotarod test nor in the number of squares crossed in the open‐field test. However, CVC decreased the number of groomings in the open‐field test. In the plus maze test, CVC, at three doses significantly increased all the observed parameters in the EPM test and flumazenil was able to reverse the effects of diazepam and CVC. Therefore, CVC did not alter the sleep latency and sleeping time in the barbiturate‐induced sleeping time test. These results show that CVC presents anxiolytic effects in the plus maze test which are not influenced by the locomotor activity in the open‐field test.

Mechanisms involved in the gastroprotective activity of esculin on acute gastric lesions in mice.

This work describes the gastroprotective actions of esculin (6,7-dihydroxycoumarin-6-o-glucoside) against indomethacin- or ethanol-induced lesions and verifies the role of nitric oxide, ATP-dependent K(+) channels, prostaglandins, transient receptor potential vanilloid 1 and antioxidant effects in the gastroprotective mechanism of esculin in the ethanol-induced gastric lesion model. The intragastric administration of esculin at doses of 12.5, 25 and 50 mg/kg was able to protect the gastric mucosa against ethanol (0.2 mL/animal p.o.), and esculin at doses of 25 and 50 mg/kg protected against indomethacin-induced lesions (20mg/kg p.o.). Administration of l-NAME (10mg/kg i.p.), glibenclamide (10mg/kg i.p.) or indomethacin (10mg/kg p.o.), but not capsazepine (5mg/kg p.o.), was able to reduce the gastroprotection promoted by esculin (25mg/kg) on the ethanol-induced lesions. Measurements of nitrite, a NO metabolite, were increased in the group that was pretreated with esculin. In terms of antioxidant activity as a gastroprotective mechanism of esculin, the results show that pre-treatment with esculin decreased the amount of GSH, increased SOD activity, did not interfere with the CAT activity and decreased both the MPO activity and the MDA amount. In conclusion, pre-treatment with esculin confers significant gastroprotective and antioxidant activity and leads to a reduction in gastric injury; the mechanisms underlying these effects include stimulation of endogenous prostaglandins, nitric oxide synthesis, opening of K(ATP) channels and reduction of free radicals or modulation of antioxidant enzyme systems.

Melatonin: Pharmacological Aspects and Clinical Trends

ABSTRACT Melatonin, N-acetyl-5-methoxytryptamine, the major hormone produced by the pineal gland under the influence of the dark/light cycle, has been shown to have a large number of therapeutic possibilities. It has been utilized in several countries for circadian rhythm disorders, sleep disturbances, jet lag, and sleep–wake cycle disturbances in blind people, and shift workers. In our mechanism of act, the Gi protein-coupled metabotropic melatonin receptors MT1 and MT2 are the primary mediators of the physiological actions of melatonin. This hormone plays an important role in the regulation of physiological and neuroendocrine functions, such as synchronization of seasonal reproductive rhythms and entrainment of circadian cycles. In addition to its chronobiological role, several pharmacological effects of melatonin have been reported in mammals including sedative, antioxidant, anxiolytic, antidepressant, anticonvulsant, and analgesic activities. There is some evidence from clinical trials that melatonin can be helpful in that event. Current trends of pharmacological functions of melatonin pointed out its use in the treatment of neurodegenerative and neoplastic diseases. These effects and uses of melatonin are mentioned but further confirmatory studies are needed in most of them.

Anxiolytic-like effect of the monoterpene 1,4-cineole in mice

Recent studies have shown that some monoterpenes exert anxiolytic- and depressant-like actions, however, these effects from monoterpene 1,4-cineole are still unknown. This work aimed to study the effects of 1,4-cineole in classic animal models for depression- and anxiety-like behavior, specifically the elevated plus maze (EPM), hole board, open field, pentobarbital sleeping time, forced swimming, tail suspension and rota rod tests. 1,4-Cineole was administered orally to mice (100, 200 and 400 mg/kg), while diazepam (1 or 2 mg/kg) and imipramine (10 or 30 mg/kg) were used as standard drugs. 1,4-Cineole (400 mg/kg) modified all parameters observed in the EPM, while no significant variation was observed on general motor activity in the open-field test. In the hole-board assay, 1,4-cineole induced increase on the number of head dips. Forced swimming and tail suspension tests showed that cineole (200 and/or 400 mg/kg) was able to promote significant increase on the immobility time, while a decreased sleep latency was observed (200 and 400 mg/kg ) on the pentobarbital sleeping time. Cineole had no effect on the motor coordination of animals in the rota rod test. The results suggest that 1,4-cineole presents potential anxiolytic-like action consistent with possible general depression of the CNS.

Anxiolytic-like effects of standardized extract of Justicia pectoralis (SEJP) in mice: Involvement of GABA/benzodiazepine in receptor

Justicia pectoralis (Acanthaceae) is used as an antiinflammatory, antimicrobial and bronchodilator, and its extract exerts an anxiolytic‐like effect profile in animal models. This work presents the behavioral effects of an aqueous standardized extract of Justicia pectoralis (SEJP) in animal models, such as the elevated plus maze (EPM), light/dark, open field, rota rod and pentobarbital sleep time. The extract was administered intragastrically to male mice at single doses of 50, 100 and 200 mg/kg, while diazepam 1 or 2 mg/kg was used as a standard drug and flumazenil 2.5 mg/kg was used to evaluate the participation of benzodiazepinic receptors. The results showed that, similar to diazepam (1 mg/kg), SEJP significantly modified all the observed parameters in the EPM test, without altering the general motor activity in the open field, rota rod and pentobarbital sleep time tests. Flumazenil reversed not only the diazepam effect but also the SEJP effect. In the same way, all doses of SEJP increased the time of permanence in the light box in the light/dark test. The results showed that SEJP presented an anxiolytic‐like effect, disproving sedative effects. Copyright

HIV antiretroviral drug Efavirenz induces anxiety-like and depression-like behavior in rats: evaluation of neurotransmitter alterations in the striatum

Abstract Efavirenz (EFV) is an effective antiretroviral drug with a favorable pharmacokinetic profile and widely used in combination regimens to treat HIV infection. However, there are major concerns about the safety of this drug. Patients treated with EFV often experience neuropsychiatric adverse effects, which frequently lead to switching to alternative EFV‐free regimens. The mechanisms involved in the central action of EFV are intrinsically unclear. Thus, this study aimed to investigate the effects of acute and subchronic (2 weeks) EFV administration in a series of behavioral tests for anxiety‐like and depression‐like behavior in healthy rats. We also evaluated the effect of EFV treatment in striatal concentrations of monoamine neurotransmitters (serotonin, dopamine and noradrenaline) and their metabolites and the amino acid neurotransmitters glutamate and GABA. Our results showed that acute treatment with EFV induced an anxiogenic‐like effect, while sub‐chronic treatment induced both anxiogenic‐like and depressive‐like behavior which was dose related. Additionally, EFV treatment caused marked alterations in the striatal concentrations of monoamines and their metabolites (and turnover rates) and the amino acid neurotransmitters glutamate and GABA. These changes were influenced by treatment duration and dose. These findings add more evidence about the neuropsychiatric adverse effects of EFV and propose potential new mechanisms for the toxic action of this drug in the central nervous system.