"Rats regulate heat dissipation with their tail because the rest is covered by fur," Rance explained. "In rats without ovaries, the lack of estrogen causes vasodilation, which we can measure as increased tail skin temperature."
"Once we knew that estrogen really does control tail skin temperature in a rat, we wanted to know what role, if any, the KNDy neurons play in this."
When Rance and her team compared the tail skin temperatures of rats with intact KNDy neurons to those with inactivated KNDy neurons, they discovered that while tail skin temperatures still followed the same ups and downs over the course of the day and night cycle, they were lower in the absence of KNDy activity.
"They have lower levels of vasodilation," Rance said. "It is very consistent. Their tail skin temperature is lower than rats with normal KNDy neurons and stays low. It doesn't matter if they have estrogen or not; it doesn't matter if it's night or if it's day."
"The rats didn't seem unhappy at all," she added. "You'd think they'd be curling up and shivering, but no. There was no difference in the core temperature, so they weren't internally cold. We did all the activity measurements and found them to be completely normal. We couldn't tell a difference other than lower vasodilatation."
Rance said she is not surprised that the same neuronal switches that are important for reproduction also control thermoregulation.
"Being able to regulate body temperature is very important for the species and also for reproduction because it is important for a pregnant woman to avoid extreme hyperthermia. Hot flushes are a symptom of hyperactivity of these neurons."
The researchers caution that while KNDy neurons are critical for normal thermoregulation, they are by no means the sole center for managing body temperature.
"These animals would be in much more trouble if that were the case," Mittelman-Smith said. "In fac
|Contact: Daniel Stolte|
University of Arizona