While other studies have examined Depo Provera's effects on bone density, Bimonte-Nelson's lab is the first to explore its effects on cognition. The researchers note that other forms of hormonal contraception, such as the pill, do not use MPA.
The study lasted approximately one year, using three groups of rats (which received doses at varying ages), plus a control group that did not receive the hormone. To test their memory, rats were placed in water-based mazes to swim and seek out hidden platforms in the water.
"What we found was pretty shocking animals that had been given the drug at any point in their life were memory impaired at middle age compared to animals that never had the drug," said Braden. "We also confirmed that in the subjects that only received the drug when young, the hormone was no longer circulating during memory testing when older, showing it had cleared from the system yet still had effects on brain function."
The researchers also measured a marker of the gamma-aminobutyric acid (GABA) neurotransmitter system in the hippocampus of the rats' brains to determine MPA's physiological effects.
"What GABA does is slow the brain down," Braden said. "So if there is too much of it, it can make it more difficult to produce memories. But then if there's too little of it and there's too much excitation, same thing it makes you not able to produce memories correctly."
The group plans to follow the animal studies with human trials, and the work is leading to results that could have profound implications for women of all ages.
"This research shows that even after this hormone is no longer on board, months and months later, resulting effects are impacting the brain and its function," Bimonte-Nelson said. "This work is an importan
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Arizona State University