Search for an antidote to electroconvulsion and lethality in aminophylline-sensitized mice

Behavioral and anticonvulsant effects of the standardized extract of Ficus platyphylla stem bark

ETHNOPHARMACOLOGICAL RELEVANCE

Decoctions of Ficus platyphylla Del.-Holl (Family: Moraceae) are used in Nigeria׳s folk medicine for the management of epilepsy and their efficacies are widely acclaimed among the rural communities of northern Nigeria. The aim of the study is to examine the behavioral and anticonvulsant properties of the standardized methanol extract of Ficus platyphylla (FP) stem bark, in order to scientifically describe its potential values in the management of convulsive disorders.

MATERIALS AND METHODS

High performance liquid chromatography (HPLC) and preliminary phytochemical analysis of the methanol extract were utilized and the intraperitoneal median lethal dose (LD50) determined in mice. The effects of FP were investigated on some murine models of behavior and its anticonvulsant effects studied on pentylenetetrazole (PTZ)-, strychnine (STN)-, picrotoxin (PCT)-, isoniazid (INH)-, aminophylline (AMI)- and maximal electroshock (MES)-induced seizures in mice.

RESULTS

The intraperitoneal oral LD50 of FP was estimated to be 5000mg/kg. FP significantly reduced the locomotor activities including the total distance covered, speed, active time and rearing counts. It shortened the onset and prolonged the duration of diazepam-induced sleep, but had no effect on motor coordination on the rota-rod treadmill or beam-walking assay in mice at the doses tested. The extract protected the mice against PTZ- and STN-induced seizures and significantly delayed the latencies of myoclonic jerks and tonic seizures induced by all the standard convulsant agents (PTZ, PCT, INH, STN and AMI) used in this study, but failed to protect the mice against MES seizures at the doses tested. The HPLC fingerprint of the extract shows a spectrum profile characteristic of Ficus platyphylla, while the preliminary phytochemical screening revealed the presence of saponins, flavonoids and tannins.

CONCLUSION

Our study provides scientific evidence that FP may contain psychoactive principles with potential anticonvulsant properties, thus supporting further development of the psychoactive components of this plant as anticonvulsant agents.

Possible role of free radicals in theophylline-induced seizures in mice

Theophylline is a methylxanthine bronchodilator with a narrow therapeutic index and is prone to induce seizures, the mechanisms for which are not clearly defined. Free radicals have considerable neurotoxic potential and the present study evaluated the possible involvement of these bioactive moieties in aminophylline-induced seizures in mice. Aminophylline (50-250 mg/kg) induced convulsions and mortality in mice in a dose-dependent manner. The anti-oxidants, melatonin (25-100 mg/kg) and N-actylcysteine (100 and 200 mg/kg) attenuated aminophylline seizures and mortality. Similar antagonism of aminophylline seizures was also observed after pretreatments with nitric oxide (NO) synthase inhibitors, L-NAME (3 and 10 mg/kg) and 7-nitroindazole (10 and 30 mg/kg). Further, combined treatment with otherwise sub-effective doses of melatonin and L-NAME or 7-nitroindazole produced marked protective effects against these seizures. Aminophylline-induced seizures enhanced malondialdehyde (MDA) concentrations and NO metabolite (NOx) levels in the brain homogenates of mice, and these were attenuated by melatonin and L-NAME pretreatments. The results are suggestive of the possible involvement of free radicals (reactive oxygen and reactive nitrogen species) in the convulsiogenic effects of aminophylline.

Effects of Saiko-ka-ryukotsu-borei-to, a Japanese Kampo medicine, on tachycardia and central nervous system stimulation induced by theophylline in rats and mice

Effects of Saiko-ka-ryukotsu-borei-to (SRBT) on theophylline-induced tachycardia in anesthetized rats and theophylline-induced locomotion and convulsions in mice were examined. An intraduodenal administration of SRBT (1 g/kg) prevented theophylline (5 mg/kg, i.v.)-induced tachycardia in rats. SRBT also attenuated an increase in arterial blood pressure with a slow reduction in heart rate of rats treated with theophylline, with no influence on the plasma level of theophylline. However, SRBT did not change the beating rate of right atrium isolated from rats in the absence or presence of theophylline or isoproterenol. The locomotor activity of theophylline in mice was reduced by the treatment with SRBT. Furthermore, the latency of convulsions in mice induced by administration of theophylline at a higher dose (240 mg/kg, i.p.) was prolonged by treatment with SRBT (1 g/kg, p.o.) and seven out of fifteen mice were saved from death due to convulsions. These results suggest that theophylline-induced tachycardia and central nervous stimulation are suppressed by SRBT and that SRBT may reduce the undesirable actions of theophylline on the cardiovascular and central nervous systems.

Dose-finding study with nimodipine: a selective central nervous system calcium channel blocker on aminophylline induced seizure models in rats

Nimodipine, a dihydropyridine derivative central nervous system (CNS) selective calcium channel blocker was studied at four different dosage schedules in five different models of seizures in rats. At a dose of 5 mg/kg, i.p. with pretreatment time of 15 min, nimodipine significantly antagonized aminophylline (175 and 200 mg/kg, i.p.), electroshock (150 mA for 0.2 s), pentylenetetrazole (60 and 75 mg/kg, i.p.), aminophylline (100 mg/kg i.p.) + electroshock (66mA for 0.2 s), and aminophylline (100 mg/kg, i.p.) + pentylenetetrazole (40 mg/kg, i.p.) induced seizures in rats. No hemodynamic alteration was observed with this dose of nimodipine. However, 2 mg/kg, i.p. (pretreatment time of 15 min and 30 min) and 5 mg/kg, i.p. (pretreatment time of 30 min) doses of nimodipine failed to demonstrate any significant anticonvulsant effect. The study highlighted the critical role of calcium ion flux into the neurons for the genesis of seizure activity to aminophylline, electroshock, and pentylenetetrazole in rats. Furthermore, the critical dose requirement for nimodipine could be explained on the basis of its short half-life and shorter duration of protection against seizures. Therefore, nimodipine may be tried clinically as an anticonvulsant in patients who are on aminophylline because of bronchial asthma or chronic obstructive pulmonary disease, when such patients have concomitant epilepsy or other seizure prone neurological deficits or are scheduled to undergo electroshock therapy.

A comparative study of aminophylline- and acepifylline-induced seizures and death in the chemoconvulsion model in rats

The convulsive, pro-convulsive and lethal effects of two theophylline-containing bronchodilating agents, aminophylline and acepifylline, have been evaluated in rats. Aminophylline (theophylline ethylenediamine) caused seizures and death in a dose-dependent manner; an intraperitoneal dose of 250 mg kg-1 caused seizures and death in all rats. Intraperitoneal doses of acepifylline (theophylline ethanoate of piperazine) up to 1000 mg kg-1, however, did not cause seizure or death. Further, pre-treatment of the rats by intraperitoneal administration of a subconvulsive dose (100 mg kg-1) of aminophylline caused a significant decrease in CD50 and LD50 values for pentylenetetrazole and a significant increase in the number of positive responders (i.e. rats with a pentylenetetrazole-induced seizure score of 3 or more on a seizure scale ranging from 0 to 6) and death rate compared with those obtained for rats pre-treated with an equivalent intraperitoneal dose (140 mg kg-1) of acepifylline ('equivalent dose' referred to here denotes the theophylline content of the two preparations). The study has established the neurosafety profile of acepifylline and documents a safer alternative to aminophylline for use in asthmatics suffering from concomitant epilepsy or other seizure-prone neurological defects.