Allopregnanolone and Pregnanolone Are Reduced in the Hippocampus of Epileptic Rats, but Only Allopregnanolone Correlates with Seizure Frequency

BACKGROUND: Neurosteroids modulate epileptic activity by interacting with the γ-aminobutyric acid type A receptor, but their brain levels are still undetermined. OBJECTIVES: We aimed to establish neurosteroid levels in the neocortex and hippocampus by liquid chromatography/mass spectrometry in epileptic rats. METHODS: Kainic acid-treated rats were continuously monitored up to 9 weeks to determine seizure frequency by video electrocorticography (n = 23) and compared to age-matched controls monitored in the same manner (n = 11). RESULTS: Decreased allopregnanolone (-50%; p < 0.05, Mann-Whitney test) and pregnanolone levels (-64%; p < 0.01) were found in the hippocampus, whereas pregnenolone sulfate, pregnenolone, progesterone, and 5α-dihydroprogesterone were nonsignificantly reduced. No changes were found in the neocortex. Moreover, allopregnanolone (but not pregnanolone) levels were positively correlated with seizure frequency (r2 = 0.4606, p < 0.01). CONCLUSION: These findings indicate a selective reduction in hippocampal levels of 3α-reduced neurosteroids. This reduction was partially mitigated by seizures in the case of allopregnanolone.