Marijuana Flashcards
(25 cards)
What is cannabis sativa?
hemp, used as a tough natural fibres
not psychoactive
illegal to grow as can be used to hide psychoactive plants
What is marijuana?
dried preparation from flowering hemp
What is the psychoactive ingredient in marijuana?
cannabinoids; ~70 different ones
- e.g. Δ9-tetrahydrocannabinol (THC)
How can the potency of THC be increased?
preventing the flower from pollinating produces a sticky resin
What are the other cannabis derivatives?
hashish-dried resin; from trichrome outgrowths of flower
hash-oil solvents; high in THC ~10-30%
What are the routes of administration and their advantages/disadvantages?
smoking; only ~20-40% of THC is absorbed
vaporising; less irritating and more controlled
ingestion; slow but strong effect
Medical uses for marijuana
glaucoma treatment antiemetic; reduces nausea and vomiting anticonvulsant enhance appetite analgesic
What is the mechanism of action of cannabinoids?
metabotropic CB1 and CB2 receptors
CB1; found primarily in the brain (basal ganglia, hippocampus, cerebellum, not brainstem)
CB2; found in the immune system, glia
Describe the pharmacokinetics of THC
highly lipid-soluble
reaches the brain very rapidly after inhalation
distributes to body fat stores hence rapid decrease in peak conc.
delay between peak plasma levels and subjective high
What are the subjective effects of marijuana?
buzz
high
stoned
What are the physiological effects of marijuana?
increased HR
blood flow to skin
appetite stimulation
red eyes; vessel dilation
What are the undesirable acute effects of marijuana?
psychotic symptoms; depersonalisation, derealisation, agitation anxiety impaired judgement motor impairment impaired memory recall
How are THC effects modelled in animals?
cannabinoids are readily discriminated from other drugs
low doses are reliably administered in monkeys
SA is highly unreliable in rats
dose-dependent effects
- Low; CPP
- High; CP aversion
What has been found using synthetic cannabinoids?
animals will reliably self-administer synthetic THC
full agonist at cb1 and 2
What is a partial agonist?
intermediate levels of intrinsic activity
becomes an antagonist in the presence of a full agonist
What is an inverse agonist?
opposite pharmacological effect at a receptor to an agonist
What is THC’s mechanism of action?
partial agonist at CB1
What is the function of CB1 receptors?
reward sensitivity
CB1 K/O seem less responsive to rewards and less accumbal DA release
inverse agonist (rimonabant) blocks THC SA
What is the mechanism of CB1R?
activation inhibits Ca2+ channels via g-protein
What are the endogenous cannabinoids, their structure and mechanism of action?
structurally unrelated to THC
anandamide; partial CB1/2 agonist
2-AG; full CB1/2 agonist
What is the functional mechanism of endogenous cannabinoids?
important regulators of synaptic transmission for glut and GABA synapses
retrograde messengers that alter the physiology of the presynaptic terminal
What is the behavioural role of endocannabinoids?
hunger
feeding; rimonbant reduces feeding, anandamide increases feeding and pleasurable response to sucrose
social play; amygdala anandamide injections increase social playing juvenile rats
What are the effects of repeated cannabinoid exposure?
mixed evidence
- many heavy users do not consume escalating doses
- tolerance can be induced in a few days in animal models
- reduced CB1R following repeated THC
- decision making and risk taking may become impaired
- withdrawal symptoms alleviated by THC
What is the risk of THC dependence?
9-10%
