Female sex steroids and epilepsy: Part 1. A review of reciprocal changes in reproductive systems, cycles, and seizures

Low-Frequency Stimulation at the Ventromedial Hypothalamus Exhibits Broad-Spectrum Efficacy Across Models of Epilepsy

AIMS

The limited efficacy and very restricted antiseizure range of current deep brain stimulation (DBS) targets highlight the need to find an optimal target for managing various seizure types. Here, we aimed to investigate the efficacy of DBS on the ventromedial hypothalamus (VMH) in the different types of experimental epileptic seizures.

METHODS

The efficacy of DBS was examined in various epileptic seizure models, and the potential mechanisms were investigated by using in vivo calcium signal recording and optogenetics.

RESULTS

The c-fos expression was significantly increased in the glutamatergic neurons of VMH (VMHglu) following seizures. Then, 1-Hz low-frequency stimulation (LFS) at the VMH successfully attenuated the seizure severities across models of epilepsy, including the maximal electroshock, the pentylenetetrazol, the absence seizure, the cortical or hippocampal kainic acid-induced acute seizure, and the hippocampal-kindling models. The in vivo calcium imaging recordings revealed that LFS could inhibit the activities of the VMHglu. Optogenetic inhibition of VMHglu mirrored LFS's antiseizure impact. Further anterograde viral tracing confirmed the extensive distributed projections of VMHglu, which may compose the circuitry basis of the broad-spectral efficacy of LFS.

CONCLUSION

These findings demonstrate that VMH-LFS is a broad-spectrum treatment approach for different seizure types by decreasing VMHglu activity.

Repeated acoustic stimulation (audiogenic kindling) induces estrous arrest in the Wistar audiogenic Rat (WAR) strain. A model of pseudopregnancy?

BACKGROUND

Epilepsy is a chronic disorder characterized by a predisposition to epileptic seizures, affecting more than 50 million people worldwide.

METHODS

Wistar and Wistar Audiogenic Rats (WAR) females were evaluated regarding estrous cycle and seizures episodes during repeated (kindling) acoustic stimulation at different stages of the estrous cycle.

RESULTS

Acoustic stimulation did not affect the estrous cycle of most Wistar females in either control (91.6 %) or kindled (70.0 %) groups. They also had no seizures episodes. In WAR females, most of the control group (91.6 %) showed regular cycles during acoustic stimulation. In the kindling group, all females showed irregular cycles during acoustic stimulation with diestrus arrest for several days (11.8 ± 1.46 days) and 12 of them (92.3 %) showed, at least, four mesencephalic seizure behaviors during the acoustic stimulation (1 ≤ cSI ≤ 8). In this group, 7 females (53.84 %) also showed limbic seizures (2 ≤ LI ≤ 4). When WAR females were stratified by estrous cycle stage, the group that started the acoustic stimulation during estrus had five females (45.4 %) with diestrus arrest for several days (11.4 ± 0.89 days) and, eight females (72.7 %) exhibited, at least, two seizure behaviors (1 < cSI < 8). When acoustic stimulation was started in the metestrus stage, six females (54.5 %) exhibited diestrus arrest for several days (10.5 ± 3.27 days). In the metestrus group, ten females (90.9 %) presented five or six seizure episodes (1 < cSI < 8).

CONCLUSION

Our results showed that chronic audiogenic seizures (audiogenic kindling) affect the estrous cycle of WAR females, resulting in a consistent diestrus arrest for 10-12 days, which is consistent with the phenomenon of pseudopregnancy.

Female sex steroids and epilepsy: Part 2. A practical and human focus on catamenial epilepsy

Catamenial epilepsy is the best described and most researched sex steroid-specific seizure exacerbation. Yet despite this there are no current evidence-based treatments, nor an accepted diagnostic tool. The best tool we currently have is tracking seizures over menstrual cycles; however, the reality of tracking seizures and menstrual cycles is fraught with challenges. In Part 1 of this two-part review, we outlined the often complex and reciprocal relationship between seizures and sex steroids. An adaptable means of tracking is required. In this review, we outline the extent and limitations of current knowledge on catamenial epilepsy. We use sample data to show how seizure exacerbations can be tracked in short/long and even irregular menstrual cycles. We describe how seizure severity, an often overlooked and underresearched form of catamenial seizure exacerbation, can also be tracked. Finally, given the lack of treatment options for females profoundly affected by catamenial epilepsy, Section 3 focuses on current methods and models for researching sex steroids and seizures as well as limitations and future directions. To permit more informative, mechanism-focused research in humans, the need for both a consistent classification of catamenial epilepsy and an objective biomarker is highlighted.