Cannabis Sativa Native to Central Asia, Cultivated for Thousands of Years for Fiber, Seeds, Medicine, Drug Use

Cannabis Sativa Native to Central Asia, Cultivated for Thousands of Years for Fiber, Seeds, Medicine, Drug Use

THC/Marijuana Marijuana/THC Overview (an intoxicant) • Cannabis Sativa native to Central Asia, cultivated for thousands of years for fiber, seeds, medicine, drug use • Main psychoactive ingredient, delta- 9-tetrahydrocannabinol (THC), from resin on unfertilized flowers • 421 chemicals (60-70 cannabinoids) • Psychoactive uses: euphoria, sedative, altered state of consciousness Marijuana Smoke vs. Tobacco Smoke • Which is more harmful? • Each type has more of certain toxins and carcinogens than other • Mitigating factors – Filtration – Additives – Frequency of use – Method of inhalation World Cannabis Highlights • Archaelogical record of hemp cord (~8000 B.C.) • Documentation of medical use in China (~2700 B.C.) • Religious use in India (~2000 B.C.) • Hashish use in Arab world (~1000 A.D.) • Western World learns of psychoactive use (mid 1800s) U.S. Cannabis History • Harvested for hemp in American colonies • Smoking introduced in 1850s by Mexicans and West Indians • Portrayed as evil in 1920s, laws passed to outlaw use • By mid-1930s, considered a “narcotic” • Marijuana Tax Act (1937): made illegal • By 1940 public convinced that it – Induced violent crimes – Led to heroin addiction – Was a great social menace U.S. Cannabis History continued • THC isolated from marijuana (1964) • Hippie era (1960s) • Synthetic marijuana - Marinol (1980) • First cannabinoid receptor isolated and cloned (1990) • Endogenous ligand (anandamide) isolated (1992) • Voters in CA, AZ approve medical use (1996) • Marinol as Schedule 3 (1999) THC Pharmacokinetics • Absorption – Inhaled (smoked) – Oral (tea, food) • Distribution – Peak blood levels in about 10 minutes – Significant depot binding due to high lipid solubility THC Pharmacokinetics continued • Metabolism and Elimination – Metabolized almost entirely by liver – Half-life 20-30+ hours (1-10 days) – More than 24 metabolites, some of which are psychoactive (e.g. 11-hydroxy-delta-9-THC) – Testing done on THC-COOH (an inactive metabolite), can be detected for several weeks – Excreted via feces (2/3) and urine (1/3) THC Pharmacodynamics • Mimics action of endogenous anandamide and sn2 arachidonylglycerol (2-AG) • Direct agonist for cannabinoid (CB) receptors, found in both CNS (CB1) and periphery (CB2) •CB1 receptors are – Metabotropic – Primarily presynaptic heteroreceptors – Mostly inhibitory • Inhibits Ach, Glu • Complex dose-related effects on reuptake and release of DA and NE • Location-specific effects on DA CB Receptor Localization • Cortex • Thalamus • Hippocampus • Cerebellum • Striatum • Accumbens • Amygdala •VTA •Retina Acute Effects • Analgesia • Euphoria • Disinhibition • Disrupted attention • Sedation • Impaired short-term • Increased appetite memory and learning • Antiemesis • Impaired multi-tasking • Altered control of motor • Altered sensory awareness movements/coordination • Hallucinations (at high • Increased heart rate and doses) blood pressure • Anxiety, fear, panic (at high doses) Chronic Effects • Respiratory system • Emotion – bronchitis, pneumonia – amotivational syndrome • Immune system • Intellect – increased likelihood of – impaired thinking/reasoning becoming ill – difficulty maintaining • Reproductive system attention – decreased sperm count • Psychological – menstrual irregularities – increasing tolerance – drug craving/seeking – addiction Possible Roles for Anandamide and 2-AG • Broaden Attentional Spotlight – Effects on cortex, thalamus, cerebellum – Wider distribution of resources – More processing of “irrelevant” stimuli • Facilitate Selective Forgetting – Effects on hippocampus –Block LTP – Facilitate rejection of “irrelevant” stimuli Medical Uses (National Academy of Sciences, 1999 •AIDS – reduces nausea, vomiting, and loss of appetite • Glaucoma – reduces intraocular pressure • Cancer – reduces side effects of chemotherapy • Multiple Sclerosis – limits muscle pain and spasticity; relieves tremors • Epilepsy – prevents seizures • Chronic Pain – alleviates pain caused by many disorders Chronic Health Effects • Cardiovascular: speeds heartbeat; risk for those with heart rhythm or blood pressure problems (but may provide protection against strokes) • Pulmonary: damage from smoke; lung cancer • Immunosuppression (but significance unclear) • Reproductive: reductions in sex hormones (sperm counts); reduces sperm mobility • Extrapolating from animal experiments, TI is estimated to be on order of 1000 Tolerance and Withdrawal • Tolerance to cardiovascular effects in both light and heavy users, but to psych effects more in heavy users • Mechanism: CB receptor downregulation and desensitization • Withdrawal precipitated in animals receiving high doses, seen in chronic heavy users who abstain: – Restlessness – Reduced food intake – Irritability – Insomnia – Agitation – Sleep disturbances – Anxiety –Nausea –Depression –Cramping .

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