OBJECTIVEThis study investigated the effects of flurothyl-induced neonatal recurrent seizures on gamma-aminobutyric acid B1 receptor (GABAB1R) expression in neonatal and adult rat brain, and explored the possible relationship between the alterations of GABAB1R in mature brain and the changes of spatial memory and seizure susceptibility in adult rats.

METHODSForty-eight postnatal day (P) 7 Sprague-Dawley rats were randomly assigned into two groups: Control and Seizure group (n=24 each). Seizures were induced by inhalant flurothyl daily for six consecutive days in rat pups from the Seizure group. Twelve rats selected randomly in each group were sacrificed on the 7th day after the last seizure for detecting the expressions of GABAB1R mRNA and protein in cerebral cortex and hippocampus by reverse transcription-polymerase chain reaction (RT-PCR) and immuno-histochemistry method. The spatial memory was tested by using the Morris water maze task during P61 to P64 and the seizure threshold was measured at P75 following intraperitoneal injection of pentylenetetrazol ( PTZ ) in the remaining rats. The rats were then sacrificed for detecting the expressions of GABAB1R mRNA and protein in cerebral cortex and hippocampus.

RESULTSThe expressions of GABAB1R mRNA and protein in the cerebral cortex on the 7th day after the last seizure and at P75 decreased significantly in the Seizure group when compared with the Control group (P < 0.05). The GABAB1R protein expression in the dentate gyrus on the 7th day after the last seizure in the Seizure group was significantly lower than that in the Control group (P < 0.05), but the GABAB1R mRNA expression in the hippocampus was not different from that in the Control group. There were no significant differences in the expressions of GABAB1R mRNA and protein in the hippocampus between the two groups at P75. The escape latencies in water maze of the rats in the Seizure group at P64 were significantly longer than those in the Control group (98,533.8 +/- 27,205.4 ms vs 46,723.3 +/- 40,666.5 ms; P <0.05). There were no differences in the seizure threshold between the two groups.

CONCLUSIONSThe expressions of GABAB1R mRNA and protein in the cerebral cortex and hippocampus of neonatal rats with recurrent seizures decreased significantly, suggesting the changes of GABAB1R may be related to acute brain injury following neonatal recurrent seizures and the memory deficit in adult rats caused by neonatal recurrent seizures.