Ben A. Chindo

Anticonvulsant properties of saponins from Ficus platyphylla stem bark

Preparations of Ficus platyphylla have been used in Nigerian traditional medicine for the management of epilepsy for many years and their efficacy is widely acclaimed among the Hausa communities of northern Nigeria. The anticonvulsant properties of the saponin rich fraction (SFG) obtained from the methanol extract of F. platyphylla stem bark were studied on pentylenetetrazole-, strychnine- and maximal electroshock seizures in mice. Effects of SFG were also examined in murine models for neurological disease and on relevant in vitro targets for anticonvulsant drugs. SFG protected mice against pentylenetetrazole- and strychnine-induced seizures; and significantly delayed the onset of myoclonic jerks and tonic seizures. SFG failed to protect mice against maximal electroshock seizures at doses tested. SFG neither abolished the spontaneous discharges induced by 4-aminopyridine in a neonatal rat brain slice model of tonic-clonic epilepsy nor could it modulate chloride currents through GABA(A) receptor channel complex in cultured cortical cells. However, it was able to non-selectively suppress excitatory and inhibitory synaptic traffic, blocked sustained repetitive firing (SRF) and spontaneous action potential firing in these cultured cells. Our results provide scientific evidence that F. platyphylla stem bark may contain psychoactive principles with potential anticonvulsant properties. SFG impaired membrane excitability; a property shared by most anticonvulsants particularly the voltage-gated sodium channel (VGSC) blocking drugs, thus supporting the isolation and development of the saponin components of this plant as anticonvulsant agents.

Pharmacological evidence favouring the use of Nauclea latifolia in malaria ethnopharmacy: Effects against nociception, inflammation, and pyrexia in rats and mice

AIM OF THE STUDY Nauclea latifolia Smith is used traditionally in the treatment of uncomplicated malaria and painful conditions among its several other applications. The objective of this study is to investigate the pharmacological activities of the plant relevant to the symptomatic treatment of malaria fever and other painful conditions as an initial step towards developing an effective therapy for the symptomatic management of malaria fever and relief of other painful conditions. MATERIALS AND METHODS Various concentrations of the aqueous extract of the root bark of this plant were evaluated for its anti-nociceptive, anti-inflammatory and anti-pyretic activities in mice and rats. Investigation of the anti-nociceptive activities was performed using the acetic acid-induced abdominal constriction and hot-plate tests in mice and formalin-induced pain test in rats, as models of nociception. The extract was also investigated for its effect against inflammation induced by egg-albumin and pyrexia induced by yeast in rats. RESULTS Our data showed that the aqueous extract of Nauclea latifolia root bark (50-200mg/kg p.o.) significantly (P<0.05) attenuated writhing episodes induced by acetic acid and increased the threshold for pain perception in the hot-plate test in mice, dose-dependently. The product also remarkably decreased both the acute and delayed phases of formalin-induced pain in rats and also caused a significant reduction in both yeast-induced pyrexia and egg-albumin-induced oedema in rats. These effects were produced in a dose-dependent manner. CONCLUSION The results suggest the presence of biologically active principles in the extract with anti-nociceptive, anti-inflammatory and anti-pyretic activities that justifies its use in malaria ethnopharmacy and subsequent development for clinical application.

Postsynaptic Dopamine (D2)-mediated Behavioural Effects of High Acute Doses of Artemisinin in Rodents

Artemisinin or qinghaosu is the active principle of quinghao (Artemisia annua L.) developed from Chinese traditional medicine, which is now widely used around the world against falciparum malaria. Behavioural effects of high acute doses of artemisinin were studied on spontaneous motor activity (SMA), exploratory behavior, apomorphine-induced stereotype behavior and pentobarbital sleeping time in mice and rats in order to provide additional evidence on its safety profile on the central nervous system (CNS). Effects of the drug on bromocriptine-induced hyperactivity in short term reserpinised mice were also evaluated. Intraperitoneal (i.p.) injection of artemisinin at doses of 50 and 100mg/kg, significantly (P<0.05) reduced the SMA in mice, prolonged the pentobarbital sleeping time in rats, and attenuated the apomorphine-induced stereotypy in mice. Mice pretreated with reserpine, showed a significant decrease in locomotor activity compared to the saline-treated group. Bromocriptine, a D(2) receptor agonist, induced locomotor activity in mice pretreated with reserpine which was attenuated by artemisinin. The results suggest that artemisinin possesses sedative property, which may be mediated via postsynaptic dopamine (D(2)) receptor in the CNS.

Behavioural Effect of Pavetta crassipes Extract on Rodents

The effects of the ethanol extract of Pavetta crassipes on the central nervous system (CNS) and on actions of some selected centrally acting drugs were studied in mice and rats. These studies were carried out using the spontaneous motor activity (SMA), amphetamine-induced hyperactivity and stereotyped behaviour, pentobarbital-induced hypnosis and exploratory activity, apomorphine-induced climbing and haloperidol-induced catalepsy in rats. The results demonstrated that the extract of P. crassipes dose-dependently decreased SMA in mice and attenuated amphetamine-induced hyperactivity and the different episodes of stereotypic behavioural patterns induced by amphetamine. In addition, the extract decreased the number of head dips in the exploratory activity test and potentiated pentobarbital-induced sleeping time in rats. Furthermore, the extract inhibited apomorphine-induced climbing in mice and potentiated haloperidol-induced catalepsy in rats. Our results suggest that the extract of P. crassipes contains biologically active substance(s) that might be acting centrally through the inhibition of dopaminergic pathway or a system linked to this pathway to mediate the observed pharmacological effects.