2 November 2011
Birth control shots linked to memory loss
by Kate Melville
Depo Provera, the hormonal birth control injection, supposedly offers a convenient alternative for women who don't want to remember to take the Pill daily. Ironically, however, new research from Arizona State University indicates that the drug may profoundly impair a person's memory. Arizona State researchers Blair Braden and Heather Bimonte-Nelson have published their findings in the journal Psychopharmacology.
The findings connect medroxyprogesterone acetate (MPA), the hormone active in Depo Provera and many popular menopausal hormone therapies, to impaired memory in rodents. Bimonte-Nelson said she and Braden began asking questions about the effects of the drug because Braden was concerned about friends taking MPA as a contraceptive. Other forms of hormonal contraception, such as the Pill, do not use MPA. "This is an important question, because what we are going to have in our future are women who are menopausal that also have a history of taking MPA as birth control when they were younger," said Bimonte-Nelson.
Carried out over one year, the study followed 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," explained 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."
"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 added. "This work is an important step forward in our understanding of the potentially long-lasting effects of clinically used hormones on brain function." She and Braden now plan to follow the animal studies with human trials.
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Source: Arizona State University