Life in Technicolor

Smoke one & read this… ‘Effects of Marijuana Smoking on the Brain The effects of marijuana on the human brain are numerous and complex. The psychoactive constituent of cannabis, delta-9 THC, affects the brain in a fundamentally different way than many other drugs, such as cocaine and opiates. These drugs are associated with the dopamine pathways within the brain and are subject to high rates of abuse, as seen with self-administration experiments done with animals. Early research on cannabis’ effects on the brain was limited by the technology of the time and was thus subject to influence by observations of behavior, rather than neuropharmacology. This lack of concrete knowledge about THC’s effects allowed cultural biases to maintain fallacy that marijuana acted similarly to heroin. Research done during the past decade, since the discovery of a THC receptor in the brain, has refuted such claims. The congressional Office of Technology Assessment found that recent research findings, especially those done by Dr. Miles Herkenham of the National Institute of Mental Health (NIMH), have proved that marijuana has no effect on the dopamine-related brain systems. (citation) Dopamine is a neurotransmitter in the brain that is associated with pleasure. The neural systems that are associated with dopamine are known as the “brain reward system.” These systems are intimately involved with limbic system, an area of the brain which is associated with the control of emotions and behavior. Highly addictive drugs, such as cocaine, affect these pathways and cause an effective increase in the amount of dopamine in the brain. Cocaine and amphetamines block the reabsorbtion of dopamine, thus prolonging and intensifying the effects. Opiates activate production of dopamine by blocking the inhibitory signal, gamma-aminobutyric acid, which would ordinarily slow or stop dopamine production. Research on animals and observations of addicts in our population has shown that animals will forsake their own personal good, whether it be refusing food and water or exposing themselves to extreme risk of contracting HIV, in order to stimulate the brain’s reward system. Whether or not a drug stimulates the dopamine-associated pathways, is a large determining factor of whether or not the drug will prove to be addictive. As coined by the Office of Technological Assessment, “The capacity to produce reinforcing effects is essential to any drug with significant abuse potential.” (citation) The OTA continued to say, “Animals will not self-administer THC in controlled studies… Cannabinoids generally do not lower the threshold needed to get animals to self-stimulate the brain reward system, as do other drugs of abuse.” Another signal that a drug has a high potential for addiction and abuse is its ability to induce tolerance. Many drugs, such as cocaine and opiates, create a tolerance by wearing out the dopamine receptors in the brain. With a percentage of the receptors being worn out with each exposure, the consumer must progressively increase the dosage to achieve the same effects. This is not the case with THC. The mammalian brain creates an equilibrium by manipulating the number of active THC receptors to effectively put a ceiling on the drug’s effectiveness. The more marijuana a person smokes, fewer THC receptors remain active. If a person rarely smokes, or only does so occasionally, the receptors will stay functioning and the “high” can be achieved with a relatively small dose. The psychological effects of marijuana are not solely due to THC. While THC is the major psychoactive ingredient that is responsible for the altered sense of reality and euphoric feelings, another constituent of the smoke, cannabinol (CBN), produces only the depressant effects. Tolerance does not develop to this chemical. The paradoxical situation this sets up is this: to maximize the desired effects, a smoker must maintain moderate use. This will keep the THC receptors active, but minimize the proportional amount of CBN ingested. For more information on the specifics of marijuana tolerance, look at Jon Gettman’s Marijuana and the Brain, Part II: The Tolerance Factor The neural toxicity of acute marijuana ingestion was tested by NIDH when they administered a 10 mg/kg dose (a dose that is frequently used in clinical research) of THC to a group of rats. This amount of THC was proportionately more than a very heavy smoker would consume in a week (the approximate equivalent of 670 inhalations from a waterpipe or 100 joints of high-quality {7.5% THC} marijuana for a 165 lb. person). (citation) The chronic (heavy, regular use) effects of marijuana consumption on the brain are disputed and the evidence available makes it difficult to draw any certain conclusions. R.G. Heath et al found, in their 1979 study of rhesus monkeys, anatomic changes in brain tissue. These changes included widening of the synaptic cleft, clumping of synaptic vesicles and other unspecified changes in morphology of brain cells. These changes were observed 6 months after cessation of 6 months of heavy exposure to marijuana smoke. The report is unclear as to its methods for morphology evaluation and controls that were used. Regardless of slight changes in brain tissue morphology, the behavior and performance levels of the monkeys returned to normal with in 8 months of cessation.(Citation)”