IACM-Bulletin of February 18, 2001

Science — Endocannabinoids play an important role in circuits responsible for vomiting

Endogenous cannabinoids produced by the human body play an important role in emetic circuits of the brain. This is the conclusion of a study by researchers of the Department of Pharmacology, Kirksville College of Osteopathic (Missouri/USA), published in the February issue of Neuropsychopharmacology.

In an animal model of vomiting with shrews they investigated the mechanism of antiemetic action of cannabinoids.

Since cannabinoids that bind to cannabinoid receptors prevent vomiting, it was hypothesized that blockade of either the cannabinoid CB1 receptor or the cannabinoid CB2 receptor would induce vomiting. Indeed the CB1 receptor antagonist SR 141716A caused emesis and both the frequency of emesis and the percentage of animals vomiting increased with increasing doses. A CB2 receptor antagonist was without effect.

These results suggest that the antiemetic activity of THC reside in its ability to stimulate the CB1 receptor. Furthermore endogenous cannabinoids seem to play an important role in circuits that are responsible for vomiting.

(Source: Darmani NA. Delta-9-tetrahydrocannabinol and synthetic cannabinoids prevent emesis produced by the cannabinoid CB(1) receptor antagonist/inverse agonist SR 141716A. Neuropsychopharmacology 2001;24(2):198-203.)

News in brief

Science

In eight glaucoma patients resistant to conventional therapies the synthetic cannabinoid WIN55212-2 decreased the intraocular pressure between about 20 and 30%. These data confirm that CB1 receptors have direct involvement in the regulation of human intraocular pressure. (Source: Porcella A, et al. Eur J Neurosci 2001;13(2):409-412.

USA

The legislature of the state of Maryland will debate whether to legalize marijuana for therapeutic uses. Patients would be allowed to possess up to seven plants and one ounce of usable marijuana. Twenty-nine delegates, including nine Republicans, have signed on to the bill, which has a hearing scheduled for 1 March. Marijuana Policy Project Executive Director Robert Kampia says that of 25 states considering legalizing marijuana for medicinal use this year, Maryland is among the three most likely to approve it. (Sources: Washington Times of 9 February 2001, NORML of 15 February 2001)

Science

THC increases sexual desire in female rats. The effect of THC was inhibited by antagonists to both progesterone and dopamine D1 receptors. The studies indicate that THC acts on the CB1 cannabinoid receptor, therewith initiating a signal transduction response that requires both membrane dopamine and intracellular progesterone receptors for effective induction of sexual behaviour. (Source: Mani SK, et al. Proc Natl Acad Sci U S A. 2001;98(3):1249-1254.)

Switzerland

53 percent of the Swiss favour legalization of use and possession of cannabis. This figure was released on 15 February by the private Swiss Institute for Alcohol and other Drug Problems. In the survey of 1,600 people between the ages of 15 and 74, 27 percent said they had used cannabis at least once in their life. About 1.2 percent said they used it daily. Five percent of people between 20 and 25 years of age reported daily use. (Source: Associated Press of 15 February 2001)

Science

A new study contradicts the idea that marijuana is a "gateway" to harder drug use, saying that appears to have been true only for the baby boom generation peaking around 1960. Writing in February's issue of the American Journal of Public Health, Andrew Golub and Bruce Johnson of the National Development and Research Institutes in New York said young people who smoked marijuana in the generations before and after the baby boomers do not appear necessarily likely to go on to use harder drugs. The researchers said these findings suggest that the gateway phenomenon reflects norms prevailing among youths at a specific place and time. (Source: Xinhua News Agency of 5 February 2001)