Behavioural effects and mechanisms of essential oils of Dennettia tripetala G. Baker (Annonaceae) in mice.

The fruits of the plant Dennettia tripetala G.Baker (Annonaceae) are well known in many communities of some southern states of Nigeria and some West African countries. They are commonly eaten as spices. We investigated the acute toxicity and behavioural effects of the essential oils of these fruits in mice and the mechanism(s) involved in the mediation of the observed behavioural effects. The result obtained showed that LD50 value of the oils in mice is 470 mg/kg (i.p.). The oils at all the dose levels used suppressed the gross behaviours and significantly (p oil treatment, atropine, naloxone and yohimbine did not reverse the inhibitory effects of the oil on locomotive activity of mice, but cyproheptadine further enhanced the inhibitory effects of the oil while flumazenil reversed significantly the inhibitory effect. These results showed that the inhibitory effect of the oil on locomotive activity is mediated through GABA-benzodiazepine and serotonergic receptors. It is concluded that the essential oil of D. tripetala may possess depressant effects on central nervous system. Keywords: Dennettia tripetala , essential oil, acute toxicity, behavioural effects, mechanisms, mice