Rat Study: Inactivity After Menopause Tied to Changes in Brain's Pleasure Center

For many women, menopause often leads to a significant drop in physical activity levels. But rather than being a simple lack of energy, inactivity after menopause may be due to changes in dopamine signaling within the brain’s pleasure center. This could lead to a lack of rewarding feelings after exercising, according to a new rat study by researchers at the University of Missouri.

The findings show that activation of the dopamine receptors in a certain part of the brain may serve as a future treatment to improve motivation for physical activity in postmenopausal women.

“Postmenopausal women are more susceptible to weight gain and health issues,” said Victoria Vieira-Potter, assistant professor of nutrition and exercise physiology at University of Missouri. “This is especially frustrating for women, who already are dealing with significant changes to their bodies. We found that the decrease in physical activity that leads to weight gain may be caused by changes in brain activity.”

For the study, the research team compared the physical activity of highly fit rats to rats that had lower fitness levels. The researchers closely observed the rats’ use of their running wheels both before and after the rats had their ovaries removed. They also examined gene expression changes of dopamine receptors within the brain’s pleasure center.

The researchers found that the high-fit rat group naturally had more activity in the brain’s pleasure center. This correlated with greater wheel running before and after the loss of ovarian hormones.

Still, the high-fit rats experienced a significant reduction in wheel running after their ovaries were removed. This reduction in physical activity was also significantly connected to a reduction in their dopamine signaling levels, indicating that the brain’s pleasure center is involved.

“We found that in both groups of rats, the hormonal changes from menopause led to changes in the brain that translated to less physical activity,” Vieira-Potter said.

“The findings confirm previous evidence in humans and rodents that weight gain that occurs after menopause is likely due to decreased overall physical activity rather than increased energy intake from diet.”

“Understanding what is causing the decrease in activity and subsequent weight gain may allow us to intervene, possibly by activating dopamine receptors, to preserve the motivation to be physically active.”

Menopause typically occurs in women between the ages of 45 and 55 with an average age of 51. As the ovaries begin to reduce their production of female hormones, estrogen and progesterone, menstruation becomes less frequent until it finally comes to a stop.

Source: University of Missouri-Columbia