Lecture 26 - Pleasure and Pain II

Question 1

Example of responses to a fearful stimulus
1)
2)
3)

Answer 1

1) Somatic nerves -> skeletal muscles. Freezing behaviour.
2) Autonomic nerve -> Smooth or cardiac muscle. Leads to increased heartrate, blood pressure, etc
3) Autonomic nerve, hormones from pituitary->endocrine gland. Hormonal release

Question 2

Definition of an emotion (EG: pain)

Answer 2

An emotion constitutes an internal, central (as in central nervous system) state, which
is triggered by specific stimuli (extrinsic or intrinsic to the organism)

Question 3

Descending pain modulation system
1)
2)
3)
4)

Answer 3

1) Starts in cortex, amygdala, hypothalamus
2) Projects down to rostral ventromedial medulla
3) Rostral ventromedial medulla (including nucleus raphae magnus 5HT neurons) projects to dorsal horn of spinal cord.
4) These modulate sensitivity of secondary neurons in spinal cord onto which nociceptors synapse

Question 4

Serotonin system
1)
2)
3)

Answer 4

1) A diffuse transmitter system (few neurons, very large number of projections)
2) Neuron cell bodies are in Raphae magnus of medulla.
3) Neurons project down spinal cord, EG: to dorsal horn, where they work with the descending pain modulation system

Question 5

Noradrenaline system
1)
2)
3)

Answer 5

1) A diffuse system
2) Neuron cell bodies are in locus coeruleus of pons
3) Can inhibit nociceptor signals in dorsal horn

Question 6

Two natural products made in opium poppy

Answer 6

Opium, codeine

Question 7

Chemical name for heroin

Answer 7

Diacetyl morphine

Question 8

Pure opioid receptor agonists

Answer 8

Morphine, fentanyl

Question 9

Opioid receptor partial agonist

Answer 9

Buprenorphine

Question 10

Opioid receptor pure antagonist

Answer 10

Naxolone.

Question 11

Drug used to reverse opioid overdose

Answer 11

Naxolone. An opioid receptor complete antagonist.

Question 12

How do norepinephrine and serotonin systems reduce nociceptor stimulation of dorsal horn neurons?
1)
2)

Answer 12

1) Directly inhibit neuron to which nociceptor projects
2) Stimulate an enkephalin interneuron, which synapses with the same dorsal horn neuron as nociceptor does, and inhibits nociceptor signal

Question 13

Major classes of centrally-acting analgesic drugs
1)
2)
3)
4)
5)
6)
7)

Answer 13

1) Opioids
2) NSAIDs
3) Anticonvulsants (EG: gabapentin)
4) Cannabinoids
5) Tricyclic antidepressants
6) Alpha2 adrenergic agonists (EG: clonidine)
7) Serotonin-noradrenaline reuptake inhibitors

Question 14

Four major classes of endogenous opioid peptides
1)
2)
3)
4)

Answer 14

1) POMC propeptide->beta-endorphin, endomorphin 1 and 2
2) Proenkephalin propeptide-> Met-enkephalin, leu-enkephalin
3) Prodynorphin->Dynorphin A, B
4) Pro-orphanin FQ propeptide->Orphanin FQ

Question 15

Opioid receptors that POMC-propeptide-derived opioids stimulate

Answer 15

Mu- and delta-opioid receptors

Question 16

Opioid receptors that pro-enkephalin opioids stimulate

Answer 16

Delta

Question 17

Opioid receptors that prodynorphin opioids stimulate

Answer 17

Kappa

Question 18

Opioids that particularly affect ascending pain pathways

Answer 18

Enkephalins, dimorphins

Question 19

Two broad sections of amygdala

Answer 19

1) Cortical amygdala - fear, learning. Necessary for learned fear responses.
2) Central amygdala - projects to the rest of brain. Coordinates fear response

Question 20

Areas involved in the psychological modulation of pain
1)
2)
3)
4)

Answer 20

1) Anterior cingulate cortex, prefrontal cortex, insula cortex
2) These project to periaqueductal grey matter in midbrain
3) These project to rostral ventromedial medulla in the midbrain.
4) Interfere with pain transmission neurons in the spinal cord

Question 21

Where do dopamine-secreting neurons reside?

Answer 21

Ventral tegmental area (substantia nigra)

Question 22

Roles of dopamine

Answer 22

Motor function

Motivation

Question 23

Dopamine relationship to reward.

Answer 23

‘Pulse’ of dopamine release from neurons when an activity occurs that warrants a reward, EG: food.
This pulse decreases in intensity the more often the events occurs (begin expecting event)

Question 24

Where does the dopamine system project to?
1)
2)
3)

Answer 24

1) Basal ganglia
2) Prefrontal cortex
3) Amygdala

Question 25

Can placebo stimulate genuine analgesia in the brain?

Answer 25

Yes. This can be blocked with naxolone.

There is overlap between places that release opioids in the brain and areas that are stimulated in placebo analgesia.