An experimental drug’s effects on the sexual behavior of certain animals is arousing interest among investigators.… The drug, para-chlorophenylalanine … reduces the level of a naturally occurring neurochemical, serotonin, in the brain of rats, mice and dogs.… Little is known about how serotonin acts in the brain, and investigators quickly recognized that PCPA could be used to study this brain chemical.
PCPA helped establish serotonin’s role in regulating sexual desire, as well as sleep, appetite and mood. The chemical messenger has become key to one common class of antidepressant drugs called selective serotonin reuptake inhibitors. Identified in 1974, SSRIs work by increasing the brain’s serotonin levels. But such drugs can hinder sexual desire. One SSRI that failed to relieve depression in humans found a second life as a treatment for sexual dysfunction. Approved by the U.S. Food and Drug Administration in 2015, this “little pink pill,” sold as Addyi, may boost sex drive in women by lowering serotonin in the brain’s reward centers.