CHICAGO, Oct. 13 (Xinhua) -- Mice with epilepsy have altered patterns of neuron activity in the portion of the brain that controls the reproductive endocrine system, University of Illinois (UI) researchers found in a study.
They also found that the differences in neuron activity in female mice fluctuate across the reproductive cycle.
The researchers studied a mouse model of epilepsy commonly used in research. The mouse estrous cycle is similar to the human menstrual cycle, although only a few days in length.
The researchers tracked hormones in the animals' blood and saw that while testosterone levels remained unaltered in male mice, female mice with epilepsy showed significant changes in levels of the hormones estradiol and progesterone.
Then they studied the firing activity of the specific neurons in the brain that trigger the body to release reproductive hormones. Across the board, neurons from mice with epilepsy were more excitable, meaning more likely to fire in response to incoming signals.
However, neuron firing activity varied among the groups. Of the epileptic mice, males and females without endocrine disruptions showed small changes in firing activity compared with the control group. Female epileptic mice with endocrine disruptions had dramatic shifts in firing activity that fluctuated across the cycle.
In female control mice, the hormone-signaling neurons had high rates of firing during one stage of the estrous cycle and lower rates of firing during another stage. However, in female mice with epilepsy and endocrine disruptions, the opposite pattern emerged.
"There are many fluctuations and dynamic changes going on during the female cycle, and signals in the mice with epilepsy are going in the wrong direction at the wrong time," said study leader Catherine Christian, a professor of molecular and integrative physiology at UI.
"We usually think of neurological changes correlated with epilepsy going in one direction at a static rate, and tailor treatments to correct that. But here, we show that one neuron population has big fluctuations in activity. At one stage of the cycle, they're showing higher rates than what would be expected, but at another point in the cycle their activity is strongly suppressed."
In the next step, the researchers plan to investigate activity both downstream from the neurons and upstream, attempting to trace the cause of the changes in neuron firing back to seizure activity.
The study has been published in the journal eNeuro.
