Objective: To study gamma-aminobutyric acid (GABA) B receptor subunits GABABR1 and GABABR2 protein expression changes after recurrent febrile seizures in the hippocampus of developing rats.
Methods: The rats were randomly divided into hyperthermia-treated group (n = 68) and control group (n = 24). According to the times of treatment, and to whether seizures developed, hyperthermia-treated group were subdivided into 4 groups: F1 (febrile, one-time, n = 12), FS1 (febrile seizure, one-time, n = 16), F10 (febrile, ten-time, n = 13), FS10 (febrile seizure, ten-time, n = 15). Immunohistochemical staining was used to demonstrate GABABR1 and GABABR2 expressions in brain sections (12 microns each).
Results: GABABR1 and GABABR2 protein expressions significantly decreased in dentate gyrus and CA1-CA3 neurons in FS10 compared with those in F10, F1, FS1 and control groups. The expressions of GABABR1 and GABABR2 protein showed less intense in F10 than those in FS1, F1 and control groups. No significant differences were observed among F1, FS1 and control group. Throughout the hippocampus, the expressions of GABABR1 and GABABR2 protein largely overlaped. GABABR1 protein expressions decreased seriously as compared with the expressions of GABABR2 protein in dentate gyrus, whereas GABABR2 protein expressions decreased more apparently in hippocampus CA1 and CA3 than that of GABABR1 in FS10.
Conclusion: Recurrent febrile seizures and recurrent hyperthermia all can make the GABABR receptor protein expression down-regulated in the immature rat brain, and GABABR protein expression decreased more apparently in recurrent febrile seizure groups than that in recurrent hyperthermia groups. These suggest that GABABR subunits may play an important role in the immature rat febrile seizures and the difference between GABABR1 and GABABR2 protein expression changes is possible as a result of subunit reorganization, which may lead to the changes of the inhibitory function.