Alumna provides advancements in sexual medicine
A University alumna conducted a recent study to provide psychologists with a new neurological understanding of female sexual behavior in rodents and a new path toward advancements in human sexual medicine.
Loretta Flanagan-Cato, who graduated from the University in 1985, studies the influence of the female sex hormones estrogen and progesterone on the brain at the end of the menstrual cycle in rodents.
Sarah Ferri-Kolwicz, a graduate student in Flanagan-Cato’s laboratory at the University of Pennsylvania, said she conceived the experiment as a part of her dissertation.
“Uncovering the estrogen-induced differences through the cycle can begin to shed light on some of the mechanisms involved in reproductive behavior,” she said.
The team infused estrogen and progesterone into the rats’ ventromedial hypothalamus, the region of brain responsible for sexual activity, Flanagan-Cato said.
She said the team wanted to see how the hormones changed the morphology of neurons, nerves that are responsible for activity in the brain.
The team found that increased estrogen levels in ventromedial hypothalamus decreased the length of long dendrites, the extended ends of neurons, and increased the density of spines, or signal transmitters, in short ones, Flanagan-Cato said.
Flanagan-Cato said progesterone treatment shortened the dendrites back to their original length. These combined levels of estrogen and progesterone at the end of menstrual cycle cause rodents to exhibit female sexual behavior.
The same occurred in prairie voles, another rodent species. Flanagan-Cato said they used prairie voles, because unlike rats, the presence of potential mates induces their menstrual cycle.
Studying the two species allowed the team to determine whether the hormones in the ventromedial hypothalamus change the structure of the dendrites when regulated under different physiological controls, she said.
“In both cases, high estrogen levels led to reproductive activeness,” Flanagan-Cato said.
She said the team then focused their study on finding a correlation between the high estrogen levels and oxytocin, another hormone involved in sexual reproduction.
The team decided to study oxytocin because they unexpectedly found oxytocin in the dendrites of neurons in the ventromedial hypothalamus, said Dipak Sarkar, a professor in the Department of Animal Sciences at the University.
Flanagan-Cato said her team found the estrogen treatment of these dendrites resulted in more activity by the ventromedial hypothalamus, but they cannot tell what this means for sexual behavior in rats.
Oxytocin is just one factor for sexual behavior, Sarkar said.
“Still, we have done lots of case studies for oxytocin. It is appearing to be useful for [explaining] the behavior,” he said.
At the moment, Flanagan-Cato said the work has missing links.
Sarkar said he thinks Flanagan-Cato and Ferri-Kolwicz’s work may eventually benefit couples troubled with impotency or other issues.
“Realistically, this [research] is applicable to humans,” he said. “At this stage, not yet. We need more done in the future, but … sexual issues have a very huge market. Anything about mating performance and behavior has its benefits.”
Ferri-Kolwicz said their work might go beyond sexual issues.
“I think this research is important in highlighting estrogen’s effects in the brain, which can have implications in neurodegenerative and psychological disorders, many of which affect men and women differently — in prevalence, progression or severity,” she said.
While this is a work in progress, Flanagan-Cato said her work at least has evolutionary significance.
“There’s a lot of dependence on female sexual behavior,” Flanagan-Cato said. “Without this behavior, there would be no reproduction or no future generations.”