Neuropharmacological effects of themethanol seed extract of cola rostrata in mice.
Cola nut is widely used in Nigeria and many West African countries as part of traditional hospitality, cultural and social ceremonies. It is known to contain caffeine, theobromine and some vitamins such as niacin and riboflavin. Cola rostrata (CR) seed has been grouped among the plants that possessed aphrodisiac effect. Comparative effect of chronic consumption of a specie “Cola nitida” and it active constituent, caffeine diet on locomotor behavior and body weights has been elucidated.This study investigated the neuropharmacological effect of the methanol extract of Cola rostrataseed in mice. This was with the objective of establishing the possible stimulant effects of the seed being a Cola specie. The seeds obtained from ripe pulp of authenticated Cola rostrata plant, were air-dried, powdered and was extracted with pure methanol. The acute toxicity test using Lorke’s method was carried out to determine oral LD50 of the plant in mice. The effects of the extract on novelty-induced behaviors (NIBs) such as open-field locomotion, rearing, and grooming in mice were evaluated. The exploratory and anxiolytic effect using hole board test were also investigated. The extract was also screened for anti-depressant and sedative activity using forced-swimming test (FST) and pentobarbitone-induced sleeping time models in mice respectively. The involvement of noradrenergic (NA) and serotonergic (5-HT) systems in the activities of the plant were also investigated by the use of NA antagonist (yohimbine) and 5-HTantagonist (cyproheptadine) to elucidate the mechanism(s) of action of the extract in depression. The results obtained showed that methanol (MeOH) extract has LD50(p.o) of 3807.89 mg/kg. The extract caused a significant (p < 0.05) inhibition of novelty-induced grooming (NIG) at 500 mg/kg and 1000 mg/kg, p.o, when compared to the vehicle control group (VEH; 10 ml/kg of 5% Tween 80). A significant (p < 0.01) reduction in the frequency of head dips was produced at 250 mg/kg in the same pattern as Chlorpromazine (0.01 mg/kg, i.p), and also a significant (p< 0.05) reduction was produced at 500 and 1000 mg/kg, p.o, compared to vehicle group. The extract at 250 mg/kg and 1000 mg/kg produced a significant (p < 0.01) reduction in latency of sleep (LOS) and significant (p < 0.05) increase in the duration of sleep (DOS) at 250 mg/kg and a significant (p < 0.01) increase in the duration of sleep at 500 mg/kg and 1000 mg/kg doses when compared to the vehicle group. which implicated that CR possessed a sedative activity at intermediate and high doses. CR at low dose produced a significant (p < 0.05) reduction of immobility time and more significant (p < 0.01) reduction when pretreated with fluoxetine (20 mg/kg,i.p) compared to vehicle group. However, pretreatment with cyproheptadine (3 mg/kg, i.p) significantly (p < 0.001) reduces the immobility time at all doses when compared to vehicle group. Pretreatment with yohimbine (1 mg/kg, i.p) also produced a significant (p < 0.01) reduction of immobility time only at low and intermediate doses compared to the vehicle group. These pretreatment with cyproheptadine or yohimbine only significantly reduced (p < 0.05) the immobility time at low dose when compared to the respective positive control groups. This study shows that the methanol extract of Cola rostratawas moderately toxic in mice and possessed a significant (p < 0.05) anti-depressant effect at low dose which could be mediated partly by serotonergic and partly by adrenergic system. It also concluded that CR possessed anxiogenic effect prominent at low dose a CNS depressant and sedative effect at intermediate and high dose.