Drugs for Pain Flashcards
Nociceptive
Sensation of pain stimuli
Pain signal –> Spinal Chord –> Brain area
Ascending Pathway
Upward signal from:
periphery –> spinal cord –> brain
Thalamus
Determines what information reached the cortex
Filters pain signal
Limbic Cortex
Emotion Processing
Descending Pathyway
Reduces pain perception because it activates the inhibitory neurons in the spinal cord that releases endorphins.
Endorphins
Regulates pain perception, appetite, wakefulness, and immunity.
1) Causes the nociceptive neuron to release less neurotransmitter
2) Cause the ascending pathway to become hyperpolarized, and less likely to fire.
Inhibitory Neurons
1) Reduce the amount of neurotransmitter that the nociceptive neuron releases
2) Reduces the excitability of the ascending pathway neurons that send the pain signal to the brain
Local Anaesthetics (lidocaine or Novocaine)
blocks the action potential of the nociceptive neurons,
NSAIDS (Non-steroidal anti-inflammatory drugs)
Drugs: ibuprofen, aspirin, and naproxen
Reduce pain and fever by reducing the production of prostaglandin, which is produced by injury and inflammation.
Opioids
Drugs: Morphine, codeine, heroin, and fentanyl
Activates the Mu Opiate Receptor: mediates pain relief
Causes the neuron to fire less and release less neurotransmitter
Opioids silence the inhibitory neurons that keep dopamine neurons quiet.
Common effects of Opioids
Euphoria, addiction, sleepiness, constipation, and breathing suppression.
Classes of Pain Medicine
1) Anesthetics
2) NSAIDS
3) Opioids
What is the receptor for morphine, heroin, and fentanyl?
Mu Opioid Receptor (MOR, a G-Protein coupled receptor)
Also, binds with Kappa and Delta Opioid Receptors
Is Morphine an agonist or antagonist of MOR?
Agonist (as is heroin and fentanyl)
Where in the body does morphine bind to reduce pain?
Morphine binds to MORs located on the terminals of nociceptors and on neurons in the dorsal horn of the spinal cord. Morphine also binds to MORs in the periaqueductal grey to reduce pain perception.
Side effects of morphine
Euphoria, constipation, slow breathing, sleep, and addiction.
Also, can cause skin rash, allergic reaction, reduced production of sex hormones.
How does lethal overdose occur (what part of the brain is morphine affecting to cause death)? How does naloxone prevent death?
Morphine reduces the activity of those neurons to slow/stop breathing. The brain loses oxygen and death ensues. Naloxone is an antagonist that competes with morphine to bind the MOR. When it binds with MOR, it blocks its activity (it’s an antagonist of the receptor instead of an agonist)
Why is morphine addictive?
- Quiets those inhibitory neurons.
- An increase in dopamine levels in the brain
- This causes euphoria
- Wanting to take the drug again
- Unpleasant withdrawal symptoms
