Methyl jasmonate ameliorates memory deficits in mice exposed to passive avoidance paradigm

Abstract

Passive avoidance task is a rodent model of memory in which the animal learnt to avoid an aversive stimulus precipitated by fear and it is always accompanied by inhibition of motor behavior. We have shown in our previous studies that methyl jasmonate (MJ), a bioactive compound isolated from Jasminum grandiflorum demonstrated memory enhancing effect in hippocampal-dependent memory tasks such as Y-maze and object recognition tests in mice. This present study was designed to investigate if MJ could ameliorate memory deficits associated majorly with the activation of the amygdala in response to an aversive stimulus in the passive avoidance paradigm. The present study also evaluated the effect of MJ on scopolamine (SC)- and lipopolysaccharide (LPS)-induced memory impairment in the passive avoidance paradigm. Mice were given intraperitoneal (i.p) injection of MJ (10-40 mg/kg), donepezil, DP (1 mg/kg) or vehicle daily for 7 days before testing for memory using passive avoidance step-down apparatus. In the interaction studies, the effects of SC (3 mg/kg, i.p.) or LPS (250 µg/kg, i.p.) given alone or with MJ (10, 20, 40 mg/kg) or DP (1 mg/kg) for 7 consecutive days were also evaluated. SC and LPS were injected 30 min after MJ or DP administration. The time it took (step-down latency) the mouse to step down from the elevated vibrating platform onto the grids (electrified stainless steel bars on the floor of the cage), which indicates memory function was recorded. Our findings revealed that MJ (10-40 mg/kg, i.p.) ameliorated memory deficits induced by electric shock in the passive avoidance test. MJ (10-40 mg/kg, i.p.) also attenuated memory impairment induced by SC (3 mg/kg) or LPS (250 µg/kg) in mice subjected to the shock in the passive avoidance task. Taken together, this study provides additional behavioral data, which further supports the potential usefulness of MJ in conditions associated with memory decline.