Uterus makes a marijuanalike compound - anandamide in mice linked to embryo development - Brief Article

Science News, April 19, 1997

In recent years, researchers have found that mammalian brains can make a compound, anandamide, whose effects resemble those of THC, the active component of marijuana (SN: 2/6/93, p. 88).

Yet the brain may not be the only anandamide producer around, or the most impressive. According to studies of pregnant mice, the uterus can synthesize this compound in massive quantities-possibly to ensure that an embryo lodges in the uterine wall at the appropriate time.

"Anandamide may determine the window of uterine receptivity for implantation," says S.K. Dey of the University of Kansas Medical Center in Kansas City.

In past studies, Dey and his colleagues found that early mouse embryos display a cell surface protein that can interact with anandamide and that exposure to the compound can impair or halt development of the embryos.

Those observations prompted Dey, Patricia C. Schmid of the University of Minnesota in Austin, and their colleagues to investigate whether the uteri of pregnant mice make anandamide.

In the April 15 Proceedings of the National Academy of Sciences, the scientists report that tissue from such uteri harbors anandamide in amounts far greater than those found in mouse brains. In fact, says Dey, the anandamide concentrations are "the highes t found in any tissue of any species."

The group also reports that anandamide concentrations in the uterus change during the early stages of a mouse's pregnancy, peaking at the same time that the uterus becomes resistant to the embryo's implantation.

The researchers further found that they could prevent embryos of recently impregnated mice from lodging in the uterus by implanting in the mice a pump that continuously releases a synthetic, anandamidelike compound.

Dey speculates that some cases of infertility result when a woman's uterus makes too much anandamide or her embryos are abnormally sensitive to the compound.

The high uterine concentrations of anandamide are "quite surprising, but if they are correct, then we have something very novel concerning pregnancy," comments Raphael Mechoulam of Hebrew University of Jerusalem, the discoverer of both THC and anandamide.

Does this new work imply that marijuana smoking alters fertility? Mechoulam is skeptical, arguing that the many epidemiological studies done on marijuana smoking have not revealed any such link.