Researchers identify clues about marijuana effects

Scientists have been studying cannabinoids, substances that are chemically related to the ingredients found in marijuana, for more than two decades, hoping to learn more about how the drug produces its effects–both therapeutic and harmful. Marijuana has been reported effective in the treatment of multiple sclerosis, glaucoma, nausea caused by chemotherapy and wasting caused by AIDS. However, like all drugs, it also causes numerous unwanted side effects, including hypothermia, sedation, memory impairment, motor impairment and anxiety. Research on cannabinoids could someday yield new, more effective drugs or drug combinations.

At Temple University’s School of Pharmacy and Center for Substance Abuse Research (CSAR), one of only a few centers in the nation focused on the basic science of substance abuse, several researchers are investigating how cannabinoids produce pharmacological effects in rats.

One such study, “L-NAME, a nitric oxide synthase inhibitor, and WIN 55212-2, a cannabinoid agonist, interact to evoke synergistic hypothermia,” published in the February issue of the Journal of Pharmacology and Experimental Therapeutics, reveals how cannabinoids produce one of the drug’s most robust actions, hypothermia, or decreased body temperature.

According to lead author Scott Rawls, Ph.D., assistant professor of pharmacodynamics at Temple’s School of Pharmacy, “To operate at maximum efficiency, the body needs to maintain a stable, normal temperature. When the body’s temperature is altered, as in hypothermia, normal body functions, such as blood pressure and circulation, are impaired.”

Marijuana operates via two receptors in the body. One receptor, called CB1, is located in the brain and produces the drug’s psychoactive effects, including euphoria and dizziness. The other receptor, CB2, is found throughout the body and impacts the immune system. Substances in marijuana bind to one of these receptors and set off a chemical process that leads to an effect, such as hypothermia. Scientists have focused on this chemical process at the molecular level to pinpoint the exact molecules involved.

Knowing that the molecule nitric oxide (NO) plays an important role in the regulation of body temperature, the Temple researchers set out to determine what role it might play in cannabinoid-induced hypothermia. By combining a cannabinoid with a substance that blocked NO synthesis, they found that cannabinoid-induced hypothermia increased more than two-fold.

“This demonstrates the possibility that NO plays a part in regulating the impact of cannabinoids on body temperature and other cannabinoid-mediated actions,” said Rawls. “These findings could be helpful in determining the mechanisms that underlie some of the pharmacological actions of marijuana,” he added.

Rawls’ research team is currently investigating the impact of cannabinoids on other physiological systems, such as analgesia and movement, and the brain neurotransmitters that mediate those systems.