opioids 1 Flashcards
what are opioids?
- narcotic (drug that affects mood/behaviour)
- produced analgesia (reduction of ability to feel pain) without anaesthesia
- promotes sense of relaxation and sleep
what does an overdose on opioids lead to?
- coma
- death
chemically, what 3 groups can opioids be divided into?
1/ opiates
2/ semisynthetic narcotics
3/ endogenous peptides
what are opiates?
- opium
- extract of the opium poppy plant
- any substances directly derived from opium
- e.g.: morphine, codeine
- natural narcotics
what are semi-synthetic narcotics?
- formed by modifying natural compounds
- chemical process
- e.g.: heroin
what are endogenous peptides?
- chemically very different
- these act on the same opioid receptors
identify acute physiological effects of opioids
- analgesia (inability to feel pain)
- cough supression
- euphoria
- relaxation
- decreased blood pressure
- reduced sex drive
- constipation
how does the molecular structure of opiates and related compounds relate to their physiological effects?
- 4 carbohydrate rings
- methyl amino groups = opioids backbone
what effect does replacing OH group with methyl oxy group have?
- codeine
- replacing hydroxy (OH) groups with methyl oxy group -> results in compound with different properties
- compound with methyl oxy group = less analgesic
- also has less side effects
- less addictive
- very potent cough suppressions
what effect does adding acetyl groups to opiates?
- heroin
- more lipophilic (mixes easier with fatty substances)
- crosses blood-brain barrier quicker
- strong high (euphoria)
- heroin converted into morphine in brain
what effect does replacing methyl group with longer carbohydrate chain?
- compound turns from compound receptor agonist to antagonist
- blocks opioid receptor
- used to treat opioid overdose
historically, what has opioids been used to against to treat?
- used against coughing, pain, diarrhoea
- nowadays, medical use = strictly regulated
- recreational use = illegal
what are the main cause of overdose deaths?
opioids
identify signs of opioid overdose
- respiratory depression
- pupil constriction (miosis)
- unresponsive (stupor)
- hypothermia
how can overdose be treated?
- injected with opioid antagonist
- naloxone
what is the suggestion that alcohol is more harmful than heroin or crack based on?
- expert assessment of drug harms to others
what type of receptors are opioid receptors?
- G-protein couples receptors
- transmembrane proteins
- sit in membrane of neurone
- via g-protein, they are coupled to other effector sites (i.e.: ion channel) or couples to intracellular signalling cascades
where can opioid receptors be found?
- CNS
- peripheral nervous system
- gastrointestinal tract
how are endogenous opioids different to opioids?
- chemically different
- these are peptides = chain of amino acids
why are there different opioid receptors?
- different receptors can exert different effects
- Kappa opioid receptor when activated = dysphoria rather than euphoria
once opioid receptor is activated, what impact does this have on neural activity?
- inhibit neural activity
- inhibit neurotransmitter release of the neurones carrying the opioid receptor
- done by neurones expressing opioid receptors
identify 3 ways that the opioid receptor may inhibit neural function
1/ post-synaptic inhibition of potassium channels (opening of K+ channels)
if potassium channels open -> makes neurone less likely to fire
2/ axoaxonic inhibition
(closing of Ca2+ channels)
opioid receptor sits on axon terminal
closing of calcium channels -> reduce release of neurotransmitter
3/ presynaptic autoreceptors
(reducing transmitter release)
neurones that co-express opioid receptor at synapse with other receptors
opioids act on this -> reduces transmitter release by that axon terminal
