The plant Parthenium hysterophorus l.was found causing toxicity in grazing animals. But the exact cause and nature of toxicity was vague till date in absence of any scientific investigation. The present study was carried out to evaluate the effect of methanol extract of parthenium hysterophorus l (PH) on psychological behavior of animals. The PH was administered orally in Swiss albino mice and the CNS effects were evaluated by general behavior, exploratory behavior, and phenobarbitone sodium induced sleeping time using standard procedures in experimental animal models.The results revealed that PH at 2.5 and 5 mg/kg caused a significant reduction in the spontaneous activity (general behavioural profile), exploratory behavioural pattern (Y maze and head dip test and significantly potentiated phenobarbitone sodium–induced sleeping time.The results conclude that the extract exhibit CNS depressant activity in tested animal models.
