Opiates and cannabinoids (Lect 6) Flashcards
Opiate definition
any drug derived from opium
e.g. morphine, codeine
Opioid defintion
any drug that is an agonist at opioid receptors in the body
endogenous opioid definition
opiate-like substance that occurs naturally in the body
e.g. endorphins
Opioids basics
comes from the opium poppy plant and contains many different opiates such as morphine and codeine
heroin: semi-synthetic opioid synthesized from morphine
acute effects: euphoria, sedation, analgesia (pain killing)
endogenous opioid systems
types: endorphins, enkephalins, dynorphins
- opioid receptor mu most studied
- mu receptors are concentrated in the limbic system (emotion and motivation), found on dopaminergic neurons in reward system
- endogenous opioids and opiates reduce noradrenic activity
- withdrawal: increases noradrenic activity: anxiety, insomnia, agitation
- play role in pain perception, responses to food, alcohol, sex, exercise
opioid antagonists
occupy opioid receptors but do not activate them
1) Naloxone: treats opiate overdose
2) Naltrexone: treats opiate addiction
pain
Opioids are most potent and effective pain killers
opioid antagonist: block pain killing effects of opioid drugs and reduces pain relief
Study on Endorphins and Placebo
Sauro and Greenberg (2005)
- when injected with an inert substance and the suggestion of pain relief: reduced reported pain
- pain perception increases for subjects with placebo when getting hidden naloxone injection
- suggests that expectation of pain relief must trigger endorphins
Eating behaviour and opioids
Yeomans and Gray (2002)
- opioid antagonists reduce short term food intake by 20%
- not due to reduced hunger more due to reduced liking of the food
- no changes in sensory qualities
- endogenous opioids modulate feeding by altering hedonic response elicited by food
- animal studies: show opioid antagonists reduce food intake for food with higher fat and sugar
- have been used to treat binge eating disorder
Alcohol &opioid antagonists
Yeomans and Gray (2002)
- daily dose of naltrexone: can reduce drinking
- effect due to reduction in cravings
- may also reduce hedonic response
- nalmefene similar to naltrexone (Scotland fist country to have available in pharmacies)
Cannabis basics
current use of population at 4% (160 million people)
- from cannabis sativa plant in herbal form: marijuana, weed
- contains hundreds of compounds including 70 different types of cannabinoids: main psychoactive ingredient is THC (agonist at receptors for endocannabinoids)
endocannabinoid system:
- endocannabinoids act as neuromodulators,
- appears to inhibit release of amino acids nt (GABA, glutamate)
plays role in: pain perception, mood, appetite, memory and learning, motor control - CB1 receptors in hippocampus, hypothalamus, basal ganglia, cerebellum and cortex
- THC is a CB1 receptor, Mimics natural occurring endocannabinoids and reduces nt release
Cannabis acute effects:
+ increased relaxation and euphoria
+ paranoia
+ mild Psychedelic effects (color perceptions)
+ hunger and food cravings
- slower task performance on complex tasks
- impaired memory learning when on drug
Study on cannabis and memory
Hooker and Jones (1987)
- 12 experienced users
- 1-3 weeks tested on two days. one day had the THC removed
- THC seemed to increase forgetting
- THC also increased intrusions like recall of memory
-
endocannabinoid system antagonists:
- cannabidiol: occurs naturally in the cannabis sativa plant and reduces psychoactive effects of THC
- has established anxiolytic effects
- Englund et al. (2013): participants either had placebo or cannabidiol
- reduced effect on memory in delayed recall
