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Definitive proof of an adverse effect of chronic marijuana use revealed at SNM's 58th Annual Meeting could lead to potential drug treatments and aid other research involved in cannabinoid receptors, a neurotransmission system receiving a lot of attention. Scientists used molecular imaging to visualize changes in the brains of heavy marijuana smokers versus non-smokers and found that abuse of the drug led to a decreased number of cannabinoid CB1 receptors, which are involved in not just pleasure, appetite and pain tolerance but a host of other psychological and physiological functions of the body.

"Addictions are a major medical and socioeconomic problem," says Jussi Hirvonen, MD, PhD, lead author of the collaborative study between the National Institute of Mental Health and National Institute on Drug Abuse, Bethesda, Md. "Unfortunately, we do not fully understand the neurobiological mechanisms involved in addiction. With this study, we were able to show for the first time that people who abuse cannabis have abnormalities of the cannabinoid receptors in the brain. This information may prove critical for the development of novel treatments for cannabis abuse. Furthermore, this research shows that the decreased receptors in people who abuse cannabis return to normal when they stop smoking the drug."

According to the National Institute on Drug Abuse, marijuana is the number-one illicit drug of choice in America. The psychoactive chemical in marijuana, or cannabis, is delta-9-tetrahydrocannabinol (THC), which binds to numerous cannabinoid receptors in the brain and throughout the body when smoked or ingested, producing a distinctive high. Cannabinoid receptors in the brain influence a range of mental states and actions, including pleasure, concentration, perception of time and memory, sensory perception, and coordination of movement. There are also cannabinoid receptors throughout the body involved in a wide range of functions of the digestive, cardiovascular, respiratory and other systems of the body. Currently two subtypes of cannabinoid receptors are known, CB1 and CB2, the former being involved mostly in functions of the central nervous system and the latter more in functions of the immune system and in stem cells of the circulatory system.

For this study, researchers recruited 30 chronic daily cannabis smokers who were then monitored at a closed inpatient facility for approximately four weeks. The subjects were imaged using positron emission tomography (PET), which provides information about physiological processes in the body. Subjects were injected with a radioligand, 18F-FMPEP-d2, which is a combination of a radioactive fluorine isotope and a neurotransmitter analog that binds with CB1 brain receptors.

Results of the study show that receptor number was decreased about 20 percent in brains of cannabis smokers when compared to healthy control subjects with limited exposure to cannabis during their lifetime. These changes were found to have a correlation with the number of years subjects had smoked. Of the original 30 cannabis smokers, 14 of the subjects underwent a second PET scan after about a month of abstinence. There was a marked increase in receptor activity in those areas that had been decreased at the outset of the study, an indication that while chronic cannabis smoking causes downregulation of CB1 receptors, the damage is reversible with abstinence.

Information gleaned from this and future studies may help other research exploring the role of PET imaging of CB1 receptors—not just for drug use, but also for a range of human diseases, including metabolic disease and cancer.

More information: Scientific Paper 10: J. Hirvonen, R. Goodwin, C. Li1, G. Terry, S. Zoghbi, C Morse, V. Pike, N. Volkow, M. Huestis, R. Innis, National Institute of Mental Health, Bethesda, MD; National Institute on Drug Abuse, Baltimore, MD; "Reversible and regionally selective downregulation of brain cannabinoid CB1 receptors in chronic daily cannabis smokers," SNM's 58th Annual Meeting, June 4-8, 2011, San Antonio, TX.
Provided by Society of Nuclear Medicine

Lµs. D schreef:Bangmakerij, het enige wat ze hier eigenlijk zeggen is dat je tolerantie opbouwt voor wiet, want dat is eig. wat tolerantie is; Een verminderde concentratie receptoren voor de betreffende stof. Oud nieuws.

The study is the first to demonstrate CB1 receptor downregulation in human chronic cannabis users, Dr. Hirvonen said.

"We have an imaging biomarker that is directly relevant to the effects of cannabis. We can use this biomarker to study the pathophysiology of various brain disorders known to be associated with cannabinoids."

Satoshi Minoshima, MD, PhD, who moderated the session, agreed that the identification of a this biomarker offers the promise of a better understanding of the effects of cannabis abuse on the brain.

"Cannabinoid receptor PET imaging is a relatively new field," said Dr. Minoshima, professor and vice chair of research in the Department of Radiology and Bioengineering and director of the Neuroimaging and Biotechnology Laboratory at the University of Washington in Seattle.

"This study is done well and provides neurochemical insights into cannabis dependency in human subjects. This is an initial study demonstrating downregulation, but I hope the authors will continue this research and correlate such neurochemical changes to clinical symptoms and addiction traits."

Lµs. D schreef:Oud nieuws.

Einstein schreef:Mja, dit kon de gemiddelde farmacologieliefhebber ook al beredeneren

Claviceps schreef:

Einstein schreef:Mja, dit kon de gemiddelde farmacologieliefhebber ook al beredeneren

Dit soort opmerking hoor ik maar al te vaak. Soms heb ik het idee dat mensen niet weten wat wetenschap inhoud...