About a third of the women who take Prozac and other selective serotonin reuptake inhibitors (SSRI) find that the antidepressants dull sexual desire and pleasure. The side effects lead some patients to stop taking the drug. Alternatives to SSRIs, such as those that modulate the neurotransmitters dopamine and norepinephrine instead of serotonin, may avoid the sexual problems. But the few studies done on these drugs, chief among them bupropion (Wellbutrin), have generated conflicting results--some found they boosted sexual interest, whereas others found they lowered it. Now the first animal study on bupropion has weighed in, and it suggests that acute doses do not dampen libido.
"Given how big a deal all this is, we were surprised to find no animal studies on it," says Skidmore College senior Gabriel Wurzel. "So we did one." Working with Hassan Lopez, professor of psychology at Skidmore, and junior Benjamin Ragen, Wurzel presented a poster session on their study October 15 at the Society for Neuroscience meeting in Atlanta.
"This is, of course, a first study, and it doesn't address long-term effects," Lopez says of the team's work on rats. "But at least for acute use, it seems to suggest bupropion has a fairly neutral effect."
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To test the rats' amorous interest, the team used a "runway apparatus." A female test rat was let into one end of a five-foot-long walled runway that ended in a "goal box"--a circular area about 18 inches across with a Plexiglas wall across its middle. The wall had a few small holes to let sound and odor pass through. The test rat's interest in any "target" placed on the barrier's far side was gauged by how long she took to get down the runway and how long she stayed once there. In this case, the team ran the test with three different targets: an empty box; a box with a nonestrus female rat; and box with male. The subject rats were in four different conditions: not in estrus; in estrus but not drugged; and then in estrus and given bupropion 45 minutes prior to the testing, with the dose doubling from the third to the fourth test.
In heat, the test females cut travel times and extended visits sharply, especially for male targets. Giving the subject females bupropion didn't cool this ardor, nor did it dampen typical displays of mating interest--back-flexing and hopping--when the females were allowed to mate with the males.
All that, noted Wurzel, was about what they expected. The one real surprise, he said, what that "the males seemed to show more interest in the females when the females had the bupropion." Neither student nor professor dared hazard a guess as to why. For an answer to that question, Lopez suggested, you'd have to ask the rats.