Nature Neuroscience pp 570 - 572 and pp 643 - 650

Testosterone is the executive that barks out orders to masculinize the fetal brain during pregnancy, but little is known about the underlings who scurry around to implement them. One such signal is prostaglandin-E₂ (PGE₂), reports a paper in the June issue of Nature Neuroscience, because drugs like aspirin that block its synthesis can interfere with brain masculinization and later male sexual behavior in rats. If this is also true in humans (which is not yet known), then there may be cause for concern about the widespread use of drugs such as aspirin and acetaminophen (commonly sold as Tylenol or Paracetemol) by pregnant women.

The authors report that male rats exposed during pregnancy or as newborns to cyclo-oxygenase inhibitors, which block the synthesis of PGE₂, show a distinct dampening of copulatory behavior in adulthood, as might occur from a reduced sex drive. They also have a reduced number of dendritic spines on neurons in a brain region known to differ between males and females, making their brains look more female as well. Female rats injected with PGE₂ show male-like copulatory behavior, and have more masculine brains than normal females. These unexpected results reinforce the conservative advice that it is prudent for women to avoid unnecessary medication during pregnancy.

An accompanying News and Views from Marc Breedlove and colleagues explains the significance of the paper. In the June editorial, Charles Jennings describes a longitudinal study already underway in the UK that may soon provide data to determine whether this finding generalizes to humans.

Nature Neuroscience pp 587 - 588

Sometimes just pretending to give a drug can alleviate the symptoms of Parkinson's disease, as long as the patient believes that the treatment is effective. Such placebo treatment works when it causes a part of the brain that is overactive as a result of the disease to return to a more normal level of activity, reports a paper in the June issue of Nature Neuroscience.

For several days, Fabrizio Benedetti and colleagues gave Parkinson's patients injections of drugs that temporarily relieved symptoms such as muscle stiffness and tremors. Then, the researchers gave the patients a placebo injection (a harmless salt solution containing no medication) without revealing the change. Before this placebo injection, the scientists surgically implanted metal wires into the brain to measure electrical signals emanating from single brain cells in a region called the subthalamic nucleus, which is hyperactive in Parkinson'ss patients. After the patients received the sham medication, these brain cells became less active and their arm muscles relaxed, allowing them to move more easily. The clinical improvement in individual patients was correlated with the changes in brain activity. These findings are the first report of placebo responses in single neurons, and may help scientists to understand how people's mental states can influence their bodies.