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.