Drugs for Pain

Question 1

Nociceptive

Answer 1

Sensation of pain stimuli

Pain signal –> Spinal Chord –> Brain area

Question 2

Ascending Pathway

Answer 2

Upward signal from:

periphery –> spinal cord –> brain

Question 3

Thalamus

Answer 3

Determines what information reached the cortex

Filters pain signal

Question 4

Limbic Cortex

Answer 4

Emotion Processing

Question 5

Descending Pathyway

Answer 5

Reduces pain perception because it activates the inhibitory neurons in the spinal cord that releases endorphins.

Question 6

Endorphins

Answer 6

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.

Question 7

Inhibitory Neurons

Answer 7

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

Question 8

Local Anaesthetics (lidocaine or Novocaine)

Answer 8

blocks the action potential of the nociceptive neurons,

Question 9

NSAIDS (Non-steroidal anti-inflammatory drugs)

Answer 9

Drugs: ibuprofen, aspirin, and naproxen

Reduce pain and fever by reducing the production of prostaglandin, which is produced by injury and inflammation.

Question 10

Opioids

Answer 10

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.

Question 11

Common effects of Opioids

Answer 11

Euphoria, addiction, sleepiness, constipation, and breathing suppression.

Question 12

Classes of Pain Medicine

Answer 12

1) Anesthetics
2) NSAIDS
3) Opioids

Question 13

What is the receptor for morphine, heroin, and fentanyl?

Answer 13

Mu Opioid Receptor (MOR, a G-Protein coupled receptor)

Also, binds with Kappa and Delta Opioid Receptors

Question 14

Is Morphine an agonist or antagonist of MOR?

Answer 14

Agonist (as is heroin and fentanyl)

Question 15

Where in the body does morphine bind to reduce pain?

Answer 15

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.

Question 16

Side effects of morphine

Answer 16

Euphoria, constipation, slow breathing, sleep, and addiction.

Also, can cause skin rash, allergic reaction, reduced production of sex hormones.

Question 17

How does lethal overdose occur (what part of the brain is morphine affecting to cause death)? How does naloxone prevent death?

Answer 17

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)

Question 18

Why is morphine addictive?

Answer 18

1. Quiets those inhibitory neurons.
2. An increase in dopamine levels in the brain
3. This causes euphoria
4. Wanting to take the drug again
5. Unpleasant withdrawal symptoms