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Prenatal exposure to stress and morphine has complicated effects on epileptic seizure. Many reports have shown an interaction between morphine- and stress-induced behavioral changes in adult rats. In the present study, effect of prenatal forced-swim stress and morphine co-administration on pentylentetrazole (PTZ)-induced epileptic behaviors was investigated in rat offspring to address effect of the interaction between morphine and stress. Pregnant rats were divided to four groups of control-saline, control-morphine, stressed-saline and stressed-morphine. In the stressed group, the rats were placed in 25 °C water on 17-19 days of pregnancy. In the morphine/saline group, the rats received morphine/saline on the same days. In the morphine/saline-stressed group, they were exposed to stress and received morphine/saline simultaneously. On postnatal day 15 (P15), blood samples were collected to determine corticosterone (COS) level. On P15 and P25, PTZ was injected to the rest of pups to induce seizure. Then, epileptic behaviors of each rat were individually observed. Latency of tonic-colonic seizures decreased in control-morphine and stressed-saline groups while increasing in stressed-morphine rats compared to control-saline group on P15. Duration of tonic-colonic seizures significantly increased in control-morphine and stressed-saline rats compared to stressed-morphine and control-saline rats on P15, but not P25. COS levels increased in stressed-saline group but decreased in control-morphine group compared to control-saline rats. Body weight was significantly higher in morphine groups than saline treated rats. Prenatal exposure to forced-swim stress potentiated PTZ-induced seizure in the offspring rats. Co-administration of morphine attenuated effect of stress on body weight, COS levels, and epileptic behaviors.

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