Acute low-dose melamine affects hippocampal synaptic plasticity and behavior in rats

Foods contaminated with melamine potentially cause risk to human health. However, the neurotoxicity of melamine has not been adequately assessed. Here, we aimed to examine the effects of acute low-dose exposure to melamine on hippocampal synaptic plasticity and behaviors in rats. We found that bath application of 50–500 μg/ml melamine decreased basal synaptic transmission in the Schaffer collateral-CA1 pathway of hippocampal slices from postnatal days (P) 10–14 rats in a concentration-dependent manner; furthermore, this decrease in transmission was related to the reduction of presynaptic function as indicated by the increased paired-pulse facilitation ratio. Rats at 2–3 months old were less vulnerable to the effects of 500 μg/ml melamine on basal synaptic transmission when compared with P10–14 and P21–28 rats. Melamine (50 μg/ml) significantly impaired long-term potentiation (LTP), without affecting long-term depression (LTD), in both P10–14 and 2–3 month-old rats. Oral treatment with melamine (5 and 25 mg/kg) 1 h before behavioral tests significantly decreased the immobility time of the forced swim test in 2–3 month-old rats and had no effect on locomotor activity in the open field test in both P21–28 and 2–3 month-old rats. Our findings reveal some of the aspects of neurotoxicity induced by acute low-dose of melamine in hippocampal synaptic plasticity and behavior.

► Neurotoxicity of acute low-dose exposure to melamine was investigated in rats. ► Melamine depressed basal synaptic transmission in the hippocampal CA1 through a presynaptic mechanism. ► Melamine impaired long-term potentiation (LTP) without affecting long-term depression (LTD). ► Melamine decreased immobility time of the forced swim test in adult rats.