Deck 5: Serotonin

Question 1

Another name for serotonin is

A) 5-hydroxytryptophan.
B) tryptophan.
C) 5-hydroxytryptamine.
D) tryptamine.

Answer 1

5-hydroxytryptamine.

Question 2

What type of meal is most likely to increase brain levels of serotonin in animals?

A) High carbohydrate, high protein
B) High carbohydrate, low protein
C) Low carbohydrate, low protein
D) Low carbohydrate, high protein

Answer 2

High carbohydrate, low protein

Question 3

Why might increasing levels of tryptophan in the blood not increase brain serotonin levels?

A) It doesn't matter how much tryptophan is present, serotonin is made at a constant rate from brain stores of tryptophan.
B) Tryptophan cannot cross the blood-brain barrier under any circumstances.
C) Tryptophan competes with other amino acids for transport across the blood-brain barrier.
D) Insulin is required for transport of tryptophan across the blood-brain barrier.

Answer 3

Tryptophan competes with other amino acids for transport across the blood-brain barrier.

Question 4

Researchers study the effects of serotonin depletion in human subjects by

A) using the synthesis blocking drug PCPA.
B) administering a special milkshake that is rich in tryptophan hydroxylase.
C) injecting subjects with insulin to alter the ratio of amino acids in the blood.
D) administering a cocktail of amino acids that compete with tryptophan for entry into the brain.

Question 5

One potential consequence of administration of an amino acid cocktail to human subjects is that

A) depressed subjects may experience a total remission of depressive symptoms if given a tryptophan-free cocktail.
B) serotonin syndrome can result.
C) previously healthy subjects can develop depression and anxiety if given a tryptophan-containing cocktail.
D) previously depressed but currently recovered patients maintained on a 5-HT-based antidepressant developed symptoms of depression if given a tryptophan-free cocktail.

Question 6

All of the following can increase the presence of serotonin in the synaptic cleft except

A) DOI.
B) MDMA.
C) fenfluramine.
D) fluoxetine.

Question 7

The activity of serotonergic neurons in humans can be determined indirectly by measuring

A) levels of 5-HIAA in cerebrospinal fluid.
B) levels of 5-HIAA in blood.
C) levels of 5-HT in cerebrospinal fluid.
D) activation of SERT.

Question 8

Later generation drugs used to treat schizophrenia, such as clozapine and risperidone, block/activate _______ receptors and produce _______ motor side effects.

A) D₂; severe
B) 5-HT_2A; fewer
C) 5-HT_2A; severe
D) both D₂ and 5-HT_2A; severe

Question 9

5,7-Dihydroxytryptamine (5,7-DHT)

A) is a metabolite of serotonin.
B) destroys the cell bodies of the serotonergic neurons.
C) inhibits serotonin synthesis.
D) must be administered directly into the brain.

Question 10

Which method(s) can be used to produce mice that lack brain serotonin throughout life, beginning with embryonic development?

A) Administering the tryptophan hydroxylase inhibitor PCPA
B) Knocking out the gene for tryptophan hydroxylase 2
C) Preventing the normal differentiation of cells that are destined to become serotonergic neurons
D) Both b and c

Question 11

In mice with a knockout of the tryptophan hydroxylase 2 gene,

A) no serotonin can be synthesized in any part of the animal's body.
B) no pharmacological treatment has been found that is able to restore serotonin, even temporarily.
C) the circuitry of the serotonergic system (fiber innervation) is normal, despite the lack of serotonin.
D) impulsive aggression is increased compared to wild-type mice.

Question 12

One brain region implicated in the neural circuitry of aggression in rodents but not in humans is the

A) amygdala.
B) cingulate cortex.
C) BNST.
D) hypothalamus.

Question 13

Evidence supporting a link between low levels of 5-HT and/or receptor activation and increased aggression, or high levels of 5-HT and/or receptor activation and decreased aggression, comes from all of the following studies except for those

A) measuring 5-HT release during play of violent video games.
B) correlating 5-HIAA concentration in the cerebrospinal fluid and measures of aggressive behavior.
C) using SSRIs to increase extracellular 5-HT levels.
D) examining inhibition of tryptophan hydroxylase.

Question 14

Evidence that serotonergic abnormalities may be involved in sudden infant death syndrome (SIDS) comes from studies showing that

A) the incidence of SIDS decreases if infants are given SSRIs.
B) response to a CO₂ challenge in mutant mice lacking central serotonin can be improved by treatment with DOI.
C) apnea in mutant mice lacking central serotonin can be reversed with SSRIs.
D) infants who died of SIDS had a reduced number of 5-HT_2A receptors in their brain.

Question 15

Administration of _______ is not likely to lead to a decrease in food intake and thus weight loss.

A) 5-HT_1B agonists
B) 5-HT_2C agonists
C) 5-HT_1A agonists
D) 5-HT₆ antagonists

Question 16

Which statement regarding serotonin and anxiety is false?

A) Buspirone is an effective antianxiety medication and a partial agonist at 5-HT_1A receptors.
B) Knockout mice lacking 5-HT_1A receptors show increased anxiety on the elevated zero maze.
C) Knockout mice lacking 5-HT_2A receptors show decreased anxiety-like behaviors.
D) The 5-HT_2A/2C receptor agonist mCPP is an effective antianxiety medication.

Question 17

Studies using animal models have shown that serotonin is involved in _______ pain.

A) cancer-related
B) neuropathic
C) hypoalgesia
D) electric shock-induced

Question 18

Administration of a 5-HT₄ receptor partial agonist

A) impairs memory consolidation in a 1-trial fear conditioning task.
B) improves cognitive function in patients with Alzheimer's disease.
C) enhances learning and memory in various learning tasks in rodents and monkeys.
D) affects cognitive function by inhibiting cholinergic transmission in the neocortex and hippocampus.

Question 19

The 5-HT₆ antagonist ________ is being tested as a potential therapeutic agent to improve cognitive function in patients with Alzheimer's disease.

A) idalopirdine
B) donepezil
C) vilazodone
D) lorcaserin

Question 20

Describe the synthesis of serotonin and explain why serotonin levels in the brain can be increased by consumption of a high-carbohydrate, low-protein meal.

Question 21

Describe the changes in dorsal raphe cell firing rate during different behavioral states in cats.

Question 22

How do 5-HT_2A receptors exert their postsynaptic effects? Give an example of a 5-HT_2A receptor agonist and a 5-HT_2A receptor antagonist.

Question 23

Describe the evidence linking serotonin and aggression in both humans and animal models. Give examples involving specific serotonin receptor subtypes.

Question 24

Imagine you are in charge of research and development of a pain medication program at a major pharmaceutical company. Assuming that you are targeting the serotonergic system in your drug development program, what pain model should you focus on? What kinds of changes in pain sensitivity have been associated with this pain model? List two different serotonergic receptors for which agonist drugs have been successful in alleviating pain in animal research.