Avaliação do potencial anticonvulsivante do extrato padronizado de Justicia pectoralis (Chambá): estudo de neuroproteção e mecanismo de ação

Abstract

Epilepsy affects about 50 million people and 30% of these people have refractory seizures to the treatment available. The mechanism of seizure involves alteration in neurotransmitters and amino acids, oxidative stress, excitotoxicity and neuronal injury. The standardized extract of Chamba (CH), prepared from the aerial parts of Justicia pectoralis, presented in previous studies anxiolytic effect related to the upregulation of GABA/benzodiazepine receptors. Thus, with the aim to investigate the anticonvulsant potential of Chamba and its mechanism of action, we performed seizure models induced by picrotoxin, strychnine, electroshock and pilocarpine. To evaluate the antioxidant activity, we measured levels of lipid peroxidation, nitrite and catalase activity in hippocampus, striatum and marrow (strychnine model) in the seizure models mentioned above. Next, we determined the levels of inhibitory amino acid (GABA, glycine, and taurine) and excitatory amino acid (glutamate and aspartate) in the hippocampus after pilocarpine seizure and, to verify neuroprotective activity, we also evaluated the percentage of neuronal damage in the CA1 and CA3 fields of hippocampus after status epilepticus induced by pilocarpine. Swiss female mice were treated orally (gavage) and divided into groups according to the study, among them: anticonvulsant activity [6 groups (n = 10): control (distilled water); CH (25, 50 and 100 mg/kg); Phenobarbital (10 mg/kg) or oxcarbazepine (60 mg/kg)], antioxidant activity [4 groups (n = 10): control (distilled water), CH (50 mg/kg), phenobarbital (10 mg/kg) or oxcarbazepine (60 mg/kg)], determination of the amino acid levels [3 groups (n = 8): control (distilled water), CH (50 mg/kg) and phenobarbital (10 mg/kg)] and verification of neuronal damage [3 groups (n = 4): control (distilled water), CH (50 mg/kg) or pilocarpine (400mg/kg, intraperitoneally). The results showed that CHAMBA presented a anticonvulsant effect because it increased latency of first convulsion and latency to death parameters in all models and doses used, except the dose of 25 mg/kg, that was not significant in picrotoxin model. The evaluation of the antioxidant activity showed that Chamba reduced levels of lipid peroxidation and nitrite, and increased catalase activity in hippocampus and striatum in all models used. The determination of amino acid levels showed that Chamba increased levels of inhibitory amino acids, and reduced levels of excitatory amino acids and, finally, the evaluation of the neuroprotective activity by the percentage of neuronal damage, Chamba showed a reduced neuronal damage in the CA1 and CA3 areas of the hippocampus. In conclusion, the study suggests a modulating action carried out by the standardized extract of Justicia pectoralis on seizures by altering levels of neurotransmitters, amino acids, oxidative stress and neuronal damage, which are the mechanisms involved in the pathology.