Abstracts

Rationale: Patients with temporal lobe epilepsy (TLE) are at higher risk of reproductive endocrine disorders. Gonadotropin-releasing hormone (GnRH) release is necessary to drive pulsatile luteinizing hormone (LH) release from the pituitary, which is required for reproductive endocrine function in both sexes. Disrupted patterns of LH release are reported in men and women with epilepsy, but underlying mechanisms are not known. Our lab has observed altered GnRH neuron firing and excitability in the intrahippocampal kainic acid (IHKA) mouse model of TLE (1). Here, we examined pulsatile rhythms of LH release and acute release of LH in response to systemic GnRH treatment in IHKA females at different estrous cycle stages.

Methods: Adult female GnRH-Cre:Ai9 mice on C57BL/6J background were injected in right dorsal hippocampus with KA (IHKA, 50 nl of 20 mM, n=8) or saline (n= 6) and implanted 2 wks later with depth EEG electrodes in ipsilateral hippocampus. EEG was collected at 2 mo post-injection for 24 h prior to and during blood sampling. EEG traces were quantified for electrographic seizures. Estrous cycle stage was recorded daily. Tail blood sampling for ultrasensitive LH assay on estrus and diestrus between 0900-1400 h (1900 h lights off) consisted of 6-μL collections every 5 min for 3 h, followed by GnRH injection (150 ng/kg i.p.) and a final tail blood sample collection 15 min later. Trunk blood was collected between 0900-1100 h for corticosterone analysis. Data were compared using 2-way ANOVA, Tukey’s post hoc tests, and Kruskal-Wallis tests.

Results: There were no differences in basal (p = 0.9) or mean (p = 0.88) LH levels between saline or IHKA mice on either diestrus or estrus. LH pulse amplitude (p = 0.99) and interpulse interval (p = 0.09) also did not differ. All mice showed higher LH after GnRH injection, but IHKA mice showed significant increases (saline diestrus: pre 1.09 ± 0.34 ng/ml, post 2.23 ± 0.44; p = 0.12; estrus: pre 0.91 ± 0.23, post 2.3 ± 0.52; p = 0.14; IHKA diestrus: pre 0.97 ± 0.60, post 2.92 ± 0.79; p < 0.0001; estrus: pre 1.00 ± 0.45, post 2.9 ± 1.57; p = 0.005). IHKA mice also showed higher pre- to post-injection differences than controls on diestrus (saline: 1.26 ± 0.46; IHKA: 1.95 ± 0.27; p = 0.006), but not on estrus (saline: 1.43 ± 0.52; IHKA: 1.90 ± 1.29; p = 0.46). There was no effect of cycle stage on EEG parameters in IHKA mice (p = 0.68), and there was no difference in corticosterone between groups at either cycle stage (saline diestrus: 2345 ± 738.03, estrus: 2571 ± 566.09, IHKA diestrus: 1638.58 ± 1166.33, estrus: 2949.50 ± 746.42 pg/ml; p = 0.22).