The influence of developmental periods of sodium valproate exposure on synaptic plasticity in the CA1 region of rat hippocampus.

The effects of chronic sodium valproate (VPA) exposure during different developmental periods on synaptic plasticity were studied in the hippocampal CA1 area. Rats were exposed to VPA (300 mg/kg per day, intraperitoneal) over different developmental intervals: (1). prenatal exposure (PR group); (2). from parturition to weaning (PW group); (3). from pregnancy day 1 to weaning (PRW group). At postnatal day 22-28, field excitatory postsynaptic potentials were recorded in the CA1 area of hippocampal slices. We found that VPA exposure in the PR and PRW groups significantly impaired long-term potentiation (LTP), long-term depression (LTD) and paired-pulse facilitation (PPF). However, exposure during lactation (PW group) only impaired LTP and had no significant effect on LTD and PPF. These results suggested that VPA exposure during lactation had the least deficits on synaptic plasticity, while VPA exposure in the PR and PRW groups seriously impaired synaptic plasticity and should be avoided.