Interaction of prenatal stress and morphine alters prolactin and seizure in rat pups

•Prenatal stress and morphine increased prolactin blood level in pup rats.•Number of tonic-clonic seizure increased in stressed and morphine treated rats.•Seizure score increased in morphine groups.•Co-administration of morphine & stress attenuated morphine/stress-induced changes.

Prenatal exposure to stress and morphine has complicated effects on epileptic seizure. In the present study, effect of prenatal forced-swim stress and morphine co-administration on pentylenetetrazol (PTZ) induced epileptic behaviors and prolactin blood level (PBL) was investigated in rat offspring. Pregnant Wistar rats were divided to four groups of control-saline, control-morphine, stressed-saline and stressed-morphine. In the stressed group, pregnant rats were placed in 25 °C water on gestation days 17, 18 and 19 (GD17, GD18 and GD19) for 30 min. In the morphine/saline group, pregnant rats received morphine (10, 12 and 15 mg/kg, IP, on GD17, GD18 and GD19, respectively) or saline (1 ml, IP). In the morphine/saline-stressed group, the rats received morphine or saline and then exposed to stress. On postnatal days 6 and 15 (P6 and P15), blood samples were obtained and PBL was determined. At P15 and P25, the rest of the pups was injected with PTZ to induce seizure. Then, epileptic behaviors of each rat were observed individually. Latency of first convulsion decreased in control-morphine and stressed-saline groups while increased in stressed-morphine rats compared to control-saline group on P15 (P = 0.04). Number of tonic-clonic seizures significantly increased in control-morphine and stressed-saline rats compared to control-saline group at P15 (P = 0.02). PBL increased in stressed-saline, control-morphine and stress-morphine groups compared to control-saline rats. It can be concluded that prenatal exposure of rats to forced-swim stress and morphine changed their susceptibility to PTZ-induced seizure and PBL during infancy and prepubertal period. Co-administration of morphine attenuated effect of stress on epileptic behaviors.