Lecture 5- Cannabis Flashcards
What are the background uses of cannabis?
-Produced from weedlike plant (Cannabis Sativa (Hemp) -Uses such as Rope, cloth, paper, seed for oil
-Over 70 other non-psychoactive agents incl Cannabidiol
What is the psychoactive agent ∆9Tetrahydocannabinol (THC)
Found in all parts of the plant but concentrated in sticky resin secreted the flowering tops of female plants.
What are the 4 forms of Cannabis?
Marijuana
Sinsemilla
Hashish (solid)
Hash oil
What is Marijuana
-Dried and crumbled leaves, small stems, flowering tops of the plant -Usually smoked in joints, pipes, bongs. -THC content varies
What is Sinsemilla?
-pollination prevented -↑ potency
What is Hashish?
-Prepared from resin -Potency varies with concentration
What is Hash oil?
-Reduced alcoholic extract -Single drop placed in a joint
What is the THC content of Cannabis?
-Typical joint contains approx. 0.5-1g of cannabis. -A joint w/ 1g of cannabis, 4% THC content, contains 40mg of THC
-THC content of samples in 1995 contain 4% THC compared to average 15% in 2015.
How does smoking Cannabis affect consumption?
-Burning marihuana results in vaporisation of THC
-THC readily absorbed through the lungs into blood plasma but only 20% of original THC is absorbed into lungs.
What is a potential way THC absorption can be increased w/ smoking?
-Absorption can be increased by breath holding eg Black et al (1998) found increased high w/ 15s hold vs 7s.
What is the half-life of cannabis?
-Half-life of 20/30 hrs, metabolism in liver and fat storage.
How does oral consumption of cannabis affect?
-Slower/delayed effects relative to smoking (smoking bypasses liver metabolism, goes straight from lungs to blood plasma).
-Effect is more sustained, due to slower metabolism and absorption into blood plasma.
What is the process of oral consumption of Cannabis?
Ingestion > Metabolism in liver > Absorbed into blood plasma.
What are Cannabinoid receptors?
Cannabis receptor = CB1 Agonist = THC Antagonist = SR141716
-Cannabis receptors active in areas consistent w/ behavioural effects eg hippocampus associated w/ spacial memory
Describe the study of Huestis et al (2001) for antagnoist effects
-Effects of marijuana attenuated by treatment of CB1 antagonist -Two groups : placebo control, SR141716 group -Responses recorded over next hour of rating of drug effect, increase in HR.
What is the Endocannabinoid system?
Given the presence of natural (endo)cannabinoids, is there a normal regulatory function of the system.
What are the effects of the CB1 antagonist from the Richardson et al (1988) study
-SR 141716 induces hyperalgesia (↑ pain sensitivity) -endocannabinoids ↓ responsiveness to pain.
What are the 3 types of behavioural effects (Iverson, 2000)?
The Buzz
The High
Being Stoned
What is ‘The buzz’ in the Iverson (2000) study
The buzz- Brief perception of dizziness, tingling sensations in extremities
What is ‘The high’ in Iverson (2000) study?
The high- Feelings of euphoria, exhilaration, disinhibition eg the giggles
What is ‘Being stoned’ in the Iverson (2000) study?
Being stoned- Reached w/ signif amount of marijuana, feelings of being calm, dreamlike. Sensations of floating and enhanced visual/auditory perception. Slowing of perception of time, changes in sociability
What is Psychopathology?
Paranoia, anxiety, panic (more likely in 1st time)
What are the physiological effects of Cannabis?
-Increased blood flow to skin (warmth sensation) -Increase in heart rate (pounding pulse) -Increase in hunger (munchies)
What is Hyperphagia?
Increased appetite and consumption
What are the cognitive deficits of Cannabis?
-Oral THC administration impairs verbal memory (Curran et al, 2002) Psychomotor functions affected eg makes driving dangerous
How is cognitive tolerance affected by cannabis?
(Hart et al, 2001)
Dose dependent=Low doses have relatively few effects (esp in heavy users)
Task dependent= If task demands are high creates impaired performance
What does the Tanda et al (2000) study suggests about rewarding effects of cannabinoids?
Phase 0: intravenous cocaine → lever press
Phase 1: extinguished with saline
Phase 2: intravenous THC → lever press
Phase 3: Effect abolished with CB1 antagonist
Phase 4: intravenous THC → lever press
What does Valjent & Maldonado (2000) say about conditioned place preference?
-Conditioned place preference w/ THC in mice -Only works if mice pre-exposed to THC in home cages (before being introduced to experimental apparatus -First experience is aversive then becomes rewarding
What is the age of initiation of Cannabis?
-Most widely used illicit drug in UK and US
-Most common in 18-21yrs
What is the definition of Tolerance?
Needing a greater dose to achieve same effect
What do human studies say about Cannabis tolerance?
Mixed result
Crompton et al (1990)- Tolerance observed following repeated administration of marijuana/pure THC.
Kirk & de Wit (1999)- Same ‘high’ in light users relative to heavy users
What do animal studies say about Cannabis use?
Consistent results
Breivogel et al (1999) w/ rats- Daily injection of THC over 3 wks and found progressive reduction in CB1 receptor density and activity and some brain areas were totally desensitised in 3wks.
What is the definition of Dependence?
Difficulty stopping taking, cravings, withdrawal symptoms.
What does the Buddy et al (2003) say about Dependence?
Found abstinence triggers irritability, anxiety, depression which resembles nicotine withdrawal symptoms. Found to be worst in first 2wks but can last for over a month.
What do animal studies say about Cannabis Dependence?
-Early studies found no effect of drug withdrawal but THC has a long half-life, so may still be in system.
What does Aceto (1996) animal study suggest about Precipitated withdrawal?
Rats given THC injections twice a day then given SR141716, symptoms of hyperactivity eg shaking, scratching. However, possible consequence of rats being stressed as it caused increased Corticotrophin releasing hormone (CRH)
How does CBT treat cannabis-use disorder?
Ppts rewarded w/vouchers for providing cannabis free urine sample.
-Moore & Budney (2003) found signif relapse. -Haney et al (2004) found withdrawal symptoms may be eased by oral THC consumption.
What were the conclusions of CBT treatment efficiency in the Haney (2004) study?
-Useful in ST but difficult to achieve in LT abstinence as only 30% had not relapsed after 180 days.
What does the Lynsky & Hall (2000) study say about Cannabis behavioural effects?
Chronic cannabis use associated w/ poor education performance eg neg attitudes, poor grades, absent from lessons.
Amotivational syndrome= Apathy, aimlessness, lack of productivity in ST and LT.
What does Fergusson et al (2003) say about Cannabis behavioural effects?
Found regular cannabis use in early life predicts poor school performance and dropout rates.
What does Solowij et al (2002) say about Cannabis cognitive effects?
Found cognitive deficits in LT users, standardised tests of learning, memory, attention. LT user deficient 1 and 7 days after exposure.
What does Pope et al (2001) say about Cannabis cognitive effects?
No difference found between heavy user and control after 28days of abstinence. Cognitive deficits linked to recent use but reversible over time.
What are the health considerations of Cannabis?
-Higher concentrations of carcinogens in cannabis smoke than tobacco
-More tar and Carbon monoxide in joint than cigarette.
What are the clinical applications of Cannabis?
-Can be tracked back thousands of years but identification of THC led to manufacture of synthetic compounds.
-Can be used for chronic pain treatment eg spinal cord injuries
-Limited widespread use due to side effects
What is the definition of Dronabinol and Nabilone?
Dronabinol: Antiemetic for chemotherapy patients
Nabilone: Appetite stimulant on AIDS patients
