Chemical composition of Zhumeria majdae essential oil and its effects on the expression of morphine withdrawal syndrome and tolerance to the anticonvulsant effect of morphine on pentylenetetrazole-induced seizures in mice / Composição química do óleo essencial de Zhumeria majdae e seus efeitos na expressão da síndrome de abstinência de morfina e tolerância ao efeito anticonvulsivante da morfina em crises induzidas por pentilenotetrazol em camundongos

Abstract Regarding the proven anticonvulsant effect of Zhumeria majdae essential oil (ZMEO) in previous studies we were prompted to investigate the ZMEO effects on the tolerance to the anticonvulsant effects of morphine and the morphine withdrawal syndrome. Tolerance to the morphine anticonvulsant effect was induced in mice by subcutaneous injection of 2.5 mg/kg of morphine for 4 days. Subsequent doses of ZMEO (20 mg/kg) were used to study the expression and development of morphine tolerance. Clonidine was used as the standard drug to inhibit the morphine withdrawal syndrome symptoms. To study the ZMEO effect on withdrawal syndrome, mice received appropriate morphine values for 4 days and on the fifth day, 60 min before administration of naloxone. The effective dose of ZMEO was determined and the number of jumps, stands and changes in the dry stool weight, as symptoms of withdrawal syndrome were evaluated. The dose of 20 mg/kg of ZMEO decreased the tolerance in development and expression groups significantly. Counting the number of jumping, standing and defecation were assessed 30 min after morphine and 1 h after the vehicle and clonidine. The dose of 40 mg/kg ZMEO decreased all the signs of withdrawal syndrome significantly. ZMEO was analyzed by GC/MS and linalool (53.1%) and camphor (23.8%) were characterized as the main components. The results suggest that ZMEO possesses constituent(s) that have activity against tolerance to the anticonvulsant effects of morphine and the morphine withdrawal symptoms.

Resumo Em relação ao efeito anticonvulsivante comprovado do óleo essencial de Zhumeria majdae (ZMEO) em estudos anteriores, fomos instigados a investigar os efeitos do ZMEO em relação à tolerância aos efeitos anticonvulsivantes da morfina e da síndrome de abstinência de morfina. A tolerância ao efeito anticonvulsivante da morfina foi induzida em camundongos por injeção subcutânea de 2,5 mg/kg de morfina por 4 dias. Doses subsequentes de ZMEO (20 mg/kg) foram utilizadas para estudar a expressão e o desenvolvimento da tolerância à morfina. A clonidina foi usada como droga padrão para inibir os sintomas da síndrome de abstinência da morfina. Para estudar o efeito do ZMEO na síndrome de abstinência, os camundongos receberam valores apropriados de morfina por 4 dias e, no 5º dia, 60 minutos antes da administração de naloxona. A dose efetiva de ZMEO foi determinada, e o número de saltos e de permanência e as alterações no peso das fezes secas, conforme os sintomas da síndrome de abstinência, foram avaliados. A dose de 20 mg/kg de ZMEO diminuiu significativamente a tolerância nos grupos de desenvolvimento e expressão. A contagem do número de saltos, permanência e defecação foi avaliada 30 minutos após a morfina e 60 minutos após o veículo e a clonidina. A dose de 40 mg/kg de ZMEO diminuiu significativamente todos os sinais da síndrome de abstinência. O ZMEO foi analisado por GC/MS, e linalol (53,1%) e cânfora (23,8%) foram caracterizados como os principais componentes. Os resultados sugerem que o ZMEO apresenta constituintes que possuem atividade contra a tolerância aos efeitos anticonvulsivantes da morfina e aos sintomas de abstinência da morfina.

Antiepileptic potential of Anisomeles indica (Linn.) Kuntze aerial parts in pentylenetetrazole-induced experimental convulsions in Wistar rats.

The chloroform (4.20% w/w), ethyl acetate (4.23% w/w) and aqueous decoction (12.11% w/w) extracts of the aerial parts of A. indica were screened for the antiepileptic activity against maximal electroshock (MES) model and pentylenetetrazole (PTZ) models at  doses of 200, 400 mg/kg, po once. Phenytoin and diazepam (25 and 2 mg/kg, ip) were used as standard drugs in MES and PTZ model, respectively. Further, ethyl acetate extract (active extract) was fractionated into flavonoid and tannin fraction, which were subsequently evaluated for the antiepileptic potential against both MES and PTZ models at a dose of 50 mg/kg, po. Pretreatment with ethyl acetate extract 200, 400 mg/kg, po, for 1 week showed significant antiepileptic activity against PTZ induced convulsions only. Isolated flavonoid fraction showed more potent antiepileptic activity as compared to ethyl acetate extract, without any neurotoxic effect. However, tannin fraction did not produce antiepileptic activity against PTZ induced convulsions. It may be concluded that the flavonoids fraction of ethyl acetate extract of aerial parts of A. indica, but not the aqueous decoction has antiepileptic potential, without producing neurotoxic effects.

CNS depressive role of aqueous extract of Spinacia oleracea L. leaves in adult male albino rats.

Treatment with Spinacia oleracea extract (SO; 400 mg/kg body weight) decreased the locomotor activity, grip strength, increased pentobarbitone induced sleeping time and also markedly altered pentylenetetrazole induced seizure status in Holtzman strain adult male albino rats. SO increased serotonin level and decreased both norepinephrine and dopamine levels in cerebral cortex, cerebellum, caudate nucleus, midbrain and pons and medulla. Result suggests that SO exerts its CNS depressive effect in PTZ induced seizure by modulating the monoamines in different brain areas.

Effect of propofol in altering pentylenetetrazol induced seizure threshold in rats.

The present study was undertaken to evaluate the role of propofol in altering pentylenetetrazol induced seizure threshold in rats. Total 42 Wistar rats were used to evaluate different parameters (onset of action, duration of seizure, seizure severity score and number of seizure) following propofol injection. The present results showed that there was significant reduction in the time required for onset of seizure in propofol treated groups following PTZ treatment. If treated with propofol alone (2 and 5 mg/kg), there was no significant difference as compared to controls. In seizure severity score assessment, there was no significant difference with various doses of propofol alone treated groups, but the difference was observed in propofol (2 and 5 mg/kg) treated groups following PTZ treatment. Duration of seizure also significantly increased in propofol (5 mg/kg) treated group, but at 2 mg/kg of propofol treatment, no significant difference was observed. The present results showed that propofol ameliorate seizure threshold and caused prolongation of duration of seizure. However, further study and trials are needed to confirm the present results.

Pro-convulsant effect of cefazolin sodium against pentylenetetrazol- or picrotoxin-induced convulsions in mice.

Cefazolin injection (3000 mg/kg, i.v.) in mice showed several behavioral excitations such as wild running, jumping, rolling, and finally undergoing severe convulsions followed by death. It's lower doses (500-2000 mg/kg, i.v.) were unable to produce any convulsions or behavioral excitations in mice. However, cefazolin (500 or 1000 mg/kg, i.v.) when administered before different doses of pentylenetetrazol (PTZ; 40 or 60 mg/kg, i.p.) or picrotoxin (PTX; 4 or 8 mg/kg, i.p.), it produced severe tonic-clonic convulsions in mice. The convulsions or behavioral excitations produced by 3000 mg/kg, i.v. cefazolin was also reversed by different doses of diazepam (0.5-2 mg/kg, i.p.) further proving the GABAergic modulatory effect of cefazolin. The results conclude the pro-convulsant action of cefazolin on PTZ- or PTX-induced convulsions, and further confirm the clinical reports.

Anticonvulsant profile of nimodipine and nitrendipine against pentylenetetrazole induced seizures in rats.

The activity of nimodipine and nitrendipine against pentylenetetrazole (PTZ) induced seizures in Albino rats was studied alone and in combination with valproate. The median effective dose [ED50] of valproate, nimodipine and nitrendipine were initially determined. All the 3 drugs were injected i.p. 30 min before the induction of seizures. Seizures were induced by PTZ 85 mg/kg i.p., and subsequently the effect of combining ED50 doses of nimodipine and nitrendipine with ED50 dose of valproate was evaluated. ED50 of valproate and nitrendipine were 129 and 2.5 mg/kg respectively. ED50 of nimodipine could not be established since a dose-response relationship was not obtained. Hence, for the purpose of combination studies, 4 mg/kg of nimodipine was used. Both nimodipine (4 mg/kg) and nitrendipine (2.5 mg/kg) decreased the ED50 of valproate from 129 to 40 mg/kg. Both nimodipine and nitrendipine potentiate the activity of valproate against PTZ induced seizures and can be considered as potential adjuvant anticonvulsants which merit further study.

Effect of sodium valproate and flunarizine administered alone and in combination on pentylenetetrazole model of absence seizures in rat.

Sodium valproate (VPA) and flunarizine (FLU) administered individually and together were examined for their effects on behavioural, and EEG changes in the pentylenetetrazole (PTZ) induced rat model of absence seizures. PTZ, 20 mg/kg, i.p., produced behavioural staring and immobility with concomitant, repetitive 7 to 9 Hz spike/wave discharges (SWDs) in EEG, monitored continuously for 1 hr and thereafter, intermittently for 4 hr, post-vehicle/drug. The number and duration (sec) of SWDs/hr were the parameters used for evaluation of vehicle vs. drug effects in normal as well as rats made epileptogenic by repeated cortical stimulation. VPA, 200 mg/kg, i.p., produced a significant reduction in the number and duration of SWDs at 20 min only in epileptogenic rats, declining to non-significant levels at 60 min, whereas FLU, 10 mg/kg i.p. had no effect on either parameter. The combination of VPA and FLU produced a highly significant reduction of the number and duration of SWDs/h for 60 min in normal and epileptogenic rats. The results provide evidence for a synergistic effect of VPA and FLU in experimental absence seizures and possible potential benefit in pharmaco resistant seizures.

Dose-related proconvulsant and anticonvulsant activity of isatin, a putative biological factor, in rats.

Isatin (indole-2, 3-dione) is an endogenous compound with anxiogenic properties, which occur within a narrow dose range (15-20 mg/kg, i.p.). Dose increment beyond 50 mg/kg, i.p. leads to the loss of anxiogenesis. Since a link has been postulated between anxiogenic and convulsant activity, the effect of a range of doses of isatin (20-80 mg/kg, i.p.) was investigated on subconvulsant and convulsant doses of two seizure-inducing agents, namely, pentylenetetrazole (PTZ) and 3-mercapto-propionic acid (3MPA) in rats. Isatin was found to induce a dose-related effect on PTZ and 3MPA convulsions. The lower dose (20 mg/kg, i.p.) potentiated PTZ and 3MPA convulsions, a median dose (40 mg/kg, i.p.) had insignificant effect, whereas higher doses (60 and 80 mg/kg, i.p.) of isatin exhibited significant anticonvulsant effect against both PTZ and 3MPA induced clonic convulsions. The investigation, thus, supports the contention that anxiogenic agents increase the susceptibility to chemical seizures. The proconvulsant effect of isatin, may be due to its inhibitory effect on central atrial natriuretic peptide receptors and stimulation of 5-hydroxytryptamine3 (5-HT3) rather than its monoamine oxidase (MAO) B inhibitory action. The anticonvulsant effect on higher doses of isatin, on the contrary, may be induced by its metabolites, including 5-hydroxyisatin.

Effect of calcium channel blockers on experimentally induced seizures in rats.

Chemically different classes of calcium channel blockers were examined in rats for their effects on behavior, tolerability and protection against maximal electroshock seizures (MES) and pentylenetetrazol (PTZ) induced seizures. In MES test at doses (mg/kg, ip) that were devoid of side effects, felodipine, 50, afforded 100% protection, while nimodipine, 5; pimozide, 10; and thioridazine, 25, showed 50 to 66% protection. Nifedipine, 10, and diltiazem, 50, showed 30 and 66% protection respectively, but were associated with side effects. Verapamil and loperamide were ineffective against MES and PTZ induced seizures. Nimodipine, 1 mg/kg, ip, was the most potent agent and produced 100% protection against PTZ. Equieffective doses were pimozide, 25, felodipine, 50, and thioridazine, 50. The rest of the calcium channel blockers showed marginal to moderate activity against chemoshock. The data obtained suggest that some calcium channel blockers possess anticonvulsant activity and may be considered as adjuvant therapeutic agents in epileptics refractory to conventional antiepileptic medication.

Pentylenetetrazol (PTZ)-kindling development in intact and subcortical structure lesioned rats.

Kindling was induced in male wistar rats (280-320 g) by daily ip injections of PTZ in subthreshold doses (30 mg/kg). Repeated administration of PTZ to animals resulted in developing of enhanced seizures and also enhanced seizure susceptibility which could be sustained for a long time (6 months) after last seizure paroxysm. The lesioned hippocampus retarded the manifestation of PTZ kindling, where as lesioned caudate nuclei increased the seizure kindling development. Results also revealed hippocampus as a determinant structure in PTZ kindling formation, which stabilize the epileptic manifestations and make them chronic, at the same time caudate nuclei retarded the epileptic seizures stabilization. This role may be only antiepileptic, and not anti-kindling as is known for caudate nuclei.

Relaçoes entre a idade e a toxidade de anestésicos locais do tipo amida em animais de experimentaçäo / Age-related toxicity by local anesthetics of the amide-type in mice

A possível variaçäo no aparecimento de convulsäo e a mortalidade pós-ictal pela administraçäo de anestésicos locais tipo amida (lidocaína e bupivacaína) e do pentilenotetrazol em relaçäo a faixa etária foram estudadas em camundongos. Apesar da origem subcortical destas convulsöes, apenas o derivado tetrazólico se mostrou convulsivante efetivo desde o período neonatal. Para os anestésicos locais houve um período de hiporresponsividade no desencadeamento de convulsäo na primeira semana de vida, embora tenha sido registrada alta incidência de mortalidade a bupivacaína, sem o aparecimento prévio de episódio convulsivo. Na época do desmame (3ª semana pós-natal) observou-se a mais alta sensibilidade as amidas anestésicas, provavelmente relacionada com o amadurecimento de núcleos relacionados com este tipo de convulsäo, como a amígdala e substantia nigra, e de sistemas de neurotransmissores facilitadores da convulsäo por anestésicos locais, como o colinérgico e o endorfínico. No grupo "geriátrico" de 365 dias houve um discreto aumento na incidência de convulsäo, mas, em relaçäo a lidocaína, evidencia-se o aumento de mortalidade pós-ictal, em comparaçäo com os animais mais jovens. Estes dados falam a favor do conceito de que a imaturidade ou deterioraçäo de núcleos e sistemas de neuro-transmissores centrais, aliadas a alteraçöes farmacocinéticas relacionadas com a idade, podem desempenhar um papel relevante na severidade da convulsäo induzida por amidas anestésicas locais na mortalidade