Abstract:
Objective. Hydroalcoholic extract of leaves of Mallotus oppositifolius (MOE), a plant used for CNS conditions in Ghana, was
investigated for acute antidepressant effects in the forced swimming (FST) and tail suspension tests (TST). Results. In both
FST and TST, MOE (10, 30, and 100 mg kg−1 ) significantly decreased immobility periods and frequencies. A 3-day pretreatment
with 200 mg kg−1 , i.p., para-chlorophenylalanine (PCPA), a tryptophan hydroxylase inhibitor, reversed the decline in immobility
and the increase of swimming score induced by MOE in the modified FST. Pretreatment with reserpine alone (1 mg kg−1 ), 𝛼-
methyldopa alone (400 mg kg−1 , i.p.), or a combination of both drugs failed to reverse the decline in immobility or the increase
in swimming score caused by the extract in the modified FST. The extract potentiated the frequency of head twitch responses
induced by 5-hydroxytryptamine. Pretreatment with d-serine (600 mg kg−1 , i.p.), glycine/NMDA agonist, abolished the behavioural
effects of MOE while d-cycloserine (2.5 mg kg−1 , i.p.), a glycine/NMDA partial agonist, potentiated it in both TST and modified
FST. Conclusion. The extract exhibited antidepressant effects in mice which is mediated by enhancement of serotoninergic
neurotransmission and inhibition of glycine/NMDA receptor activation.
