Deck 6: Serotonin

Question 1

A specific marker for serotonin cells is

A) tyrosine hydroxylase (TH).
B) tryptophan hydroxylase (TPH).
C) AADC.
D) MAO.

Answer 1

B

Question 2

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

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

Answer 2

B

Question 3

Most of the tryptophan obtained through diet is converted to _______, through the actions of _______.

A) glucose; MAO and IDO
B) kynurenine; IDO or TDO
C) glucose; MAO or COMT
D) kynurenine; COMT or TDO

Answer 3

B

Question 4

Why might increasing levels of tryptophan in the bloodstream not increase brain serotonin levels as would be expected?

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.

Question 5

In order to study the effects of serotonin depletion in rodent studies,

A) tryptophan hydroxylase is inhibited by injection of para-chlorophenylalanine (PCPA).
B) tryptophan hydroxylase is stimulated by injection of para-chlorophenylalanine (PCPA).
C) animals are fed a high carbohydrate, low protein diet.
D) insulin is injected to alter the ratio of amino acids in the blood.

Question 6

Researchers study the effects of serotonin depletion in human subjects by inducing _______, which is accomplished by _______.

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

Question 7

One potential consequence of acute tryptophan depletion, (ATD) therapy is that

A) it can impair working memory.
B) it can lead to serotonin syndrome.
C) patients with clinical depression taking an antidepressants that act on the adrenergic system may experience a relapse in their symptoms.
D) patients with clinical depression taking an antidepressants that act on the serotonergic system may experience a relapse in their symptoms.

Question 8

All of the following drugs result in an increase in serotonin levels except

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

Question 9

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) Creating knockout mice that lack 5-HT
C) Preventing the normal differentiation of cells that are destined to become serotonergic neurons
D) Both b and c

Question 10

Findings based on ATD and tyrosine hydroxylase inhibitor depletion studies support the theory that the underlying causes of differing symptoms among people with mood or anxiety disorders may be related to abnormalities in

A) signaling among peptide hormones.
B) the parasympathetic versus the sympathetic nervous systems.
C) the limbic system.
D) the serotonergic versus the catecholaminergic systems.

Question 11

Autoreceptors on serotonin terminals are of the _______ subtype, while somatodendritic autoreceptors are of the _______ subtype.

A) 5-HT_1A; 5-HT₃
B) 5-HT_1A; 5-HT_1B or 5-HT_1D
C) 5-HT_1B or 5-HT_1D; 5-HT_1A
D) 5-HT₃; 5-HT_1A

Question 12

The deactivation and metabolism of serotonin

A) involves reuptake by COMT.
B) can be increased by SSRIs like Prozac.
C) is selectively affected by the neurotoxin MDMA.
D) yields the metabolite 5-HIAA.

Question 13

Knockout mice lacking the serotonin transporter SERT exhibit all of the following except

A) hypoactivity.
B) a decrease in aggressiveness.
C) enhanced maternal behavior.
D) anxiety-like behavior.

Question 14

If a researcher was exploring a possible link between the activity of serotonergic neurons and behavioral traits in a group of people with personality disorders, she might measure in _______ in these subjects.

A) levels of 5-HIAA in the CSF
B) levels of 5-HIAA in the bloodstream
C) levels of 5-HT in the CSF
D) activity of SERT

Question 15

MDMA was originally synthesized by the Merck pharmaceutical company as part of a project to find new substances that would

A) reduce appetite.
B) stop bleeding.
C) reduce anxiety or nervousness.
D) increase energy.

Question 16

Which statement about MDMA is false?

A) It produces an altered state of consciousness.
B) It has been proposed as an adjunct to psychotherapy because it can enhance empathy.
C) It has definitively been shown to produce degeneration of nerve fibers in all human users.
D) It is considered a Schedule I substance according to the DEA.

Question 17

MDMA has been shown to improve the clinical response in patients undergoing treatment for

A) PTSD.
B) drug addiction.
C) anorexia.
D) depression.

Question 18

The principal acute action of MDMA is to

A) prevent reuptake of serotonin.
B) inhibit synthesis of serotonin.
C) enhance tryptophan transport.
D) enhance serotonin release.

Question 19

_______ syndrome is caused by neuroendocrine tumors that release an overabundance of _______ into the bloodstream.

A) Carcinoid; 5-HT
B) Serotonin; α-MSH
C) Carcinoid; Ca²⁺
D) Serotonin; K⁺

Question 20

Most of the cell bodies that produce serotonin in the CNS are found in the

A) cerebellum.
B) raphe nuclei.
C) thalamus.
D) limbic system.

Question 21

The fibers of serotonergic neurons are found

A) mainly in the cerebellum and spinal cord.
B) mainly in the midbrain, hypothalamus, and thalamus.
C) mainly in the midbrain, pons, and medulla.
D) in virtually all forebrain areas.

Question 22

Serotonergic neurons in the cat dorsal raphe nucleus stop firing during which behavioral state?

A) REM sleep
B) Active waking
C) Slow-wave sleep
D) Quiet waking

Question 23

Experiments with mice show that slow, tonic firing of DRN neurons promotes _______, while burst firing of these neurons promotes _______.

A) hyperactivity; sedation
B) aggression; fear
C) sleep; wakefulness
D) anorexia; feeding behavior

Question 24

Pharmacologists have identified at least _______ different receptor subtypes for serotonin, most of which are _______.

A) 14; ionotropic
B) 7; ionotropic
C) 7; metabotropic
D) 14; metabotropic

Question 25

All serotonin receptors are _______ except for the _______ receptor, which is _______.

A) metabotropic; 5-HT_5B; ionotropic
B) metabotropic; 5-HT₃; ionotropic
C) ionotropic; 5-HT_2C; metabotropic
D) ionotropic; 5-HT_1C; metabotropic

Question 26

Which statement about 5-HT_1A receptors is false?

A) They serve as somatodendritic autoreceptors in the dorsal raphe nuclei.
B) They are located postsynaptically in the forebrain.
C) They serve as autoreceptors on serotonergic axon terminals in the forebrain.
D) They are concentrated in the hippocampus, septal area, and parts of the amygdala.

Question 27

Activation of 5HT_1A serotonin receptors can result in all of the following except a(n)

A) increase in Na⁺ conductance across the cell membrane.
B) reduction in cAMP synthesis.
C) increase in K⁺ conductance.
D) decrease in firing of the serotonergic neuron.

Question 28

Activation of 5HT_1A serotonin receptors causes the neuronal membrane to be _______ because _______ channels are opened.

A) hyperpolarized; K⁺
B) depolarized; K⁺
C) hyperpolarized; Ca²⁺
D) depolarized; Na⁺

Question 29

Information regarding the effects of endogenous 5-HT on 5-HT_1A receptors can be determined by administration of an antagonist such as

A) buspirone.
B) 8-OH-DPAT.
C) WAY-100635.
D) ipsapirone.

Question 30

Like α₁-adrenergic receptors, _______ receptors activate the phosphoinositide second-messenger system and thus increase intracellular _______ levels.

A) 5-HT_2A; Ca²⁺
B) 5-HT_1A; K⁺
C) 5-HT_2A; cAMP
D) 5-HT_2A; Na⁺

Question 31

Which statement regarding the serotonin receptor family is true?

A) 5-HT_1A receptors are located primarily in the cerebral cortex.
B) 5-HT_2A receptors cause inhibition by decreasing adenyl cyclase and increasing potassium efflux.
C) There is a family of five different 5-HT₁ receptors.
D) LSD and similar hallucinogens are most likely agonists at the 5-HT_1A receptor.

Question 32

Drugs that act as agonists at 5-HT_2A receptors produce a characteristic "head-twitch" response in rodents, and _______ in humans.

A) unwanted motor responses
B) hallucinations
C) Parkinsonian symptoms
D) antischizophrenic effects

Question 33

Anti-migraine drugs known as triptans act as _______ and cause _______ of blood vessels.

A) 5HT_1A agonists; constriction
B) 5-HT₃ antagonists; dilation
C) 5-HT_1B/1D antagonists; constriction
D) 5-HT_1B/1D agonists; constriction

Question 34

Traditional medications used to treat migraines work by constricting blood vessels. In contrast the 5-HT1F agonist lasmiditan acts by

A) decreasing activity within the pain pathway.
B) increasing release of endorphins.
C) reducing blood pressure.
D) enhancing vagal transmission of serotonin to the brain.

Question 35

Which statement regarding 5-HT₃ receptors is false?

A) Some of them are located on peripheral terminals of the vagus nerve.
B) Activation of these receptors inhibits the vomiting center in the brainstem.
C) Drugs that block this receptor subtype are used to treat nausea in cancer chemotherapy patients.
D) Ondansetron, granisetron, and palonosetron are all 5-HT₃ receptor antagonists.

Question 36

Mice genetically engineered to lack central serotonin

A) do not survive to birth.
B) demonstrate little to no aggressive behavior.
C) have difficulty with thermoregulation.
D) breathe at a faster rate than wild-type mice.

Question 37

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 studies

A) measuring 5-HT release during play of violent video games.
B) correlating 5-HIAA concentration in the CSF and brain to measures of aggressive behavior.
C) using PCPA to increase extracellular 5-HT levels.
D) determining the ratio TPH to 5H-T in the bloodstream.

Question 38

A mouse is tested in the elevated plus-maze and shows extreme anxiety compared to other mice. From this observation you surmise that this mouse likely

A) is a 5-HT₄-knockout mouse.
B) has been treated with a selective 5-HT_2C agonist.
C) is a 5-HT_1A-knockout mouse.
D) has been treated with a 5-HT_1A receptor agonist.

Question 39

Similar brain areas have been shown to be involved in fear/anxiety and aggression. Thus, before reacting to a threat a person evaluates present context and past experience, which dictates whether the person's response to the threat is _______ or _______.

A) defensive; aggressive
B) delayed; immediate
C) unpredictable; predictable
D) overreactive; underreactive

Question 40

Which scenario provides evidence supporting the serotonin deficiency hypothesis?

A) Mice administered PCPA show a decrease in aggressive behavior.
B) A person with impulsive aggression is prescribed a relatively high dose of an SSRI, which reduces this behavior.
C) Mice are fed a diet high in tryptophan and show an increase in aggressive behavior.
D) A person with impulsive aggression is treated with ATD, which reduces this behavior.

Question 41

Administration of _______ leads to a decrease in food intake, weight loss and other benefits for people that are overweight, such as lowering diabetes risk.

A) 5-HT₄ agonists
B) 5-HT_2C agonists
C) 5-HT₃ antagonists
D) 5-HT₆ antagonists

Question 42

In the gut, serotonin is synthesized by

A) some neurons within the enteric nervous system.
B) enterochromaffin cells.
C) goblet cells.
D) Both a and b

Question 43

Serotonin release in the gut is stimulated by

A) triptan drugs.
B) fasting.
C) entry of food into the gut.
D) anxiolytic drugs.

Question 44

One of the current treatments for irritable bowel syndrome IBS-D is alosetron, which acts as a

A) 5-HT₃ antagonist.
B) 5-HT₆ agonist.
C) 5-HT₄ antagonist.
D) 5-HT₂ agonist.

Question 45

The hypothalamic circuit that includes neuropeptide-releasing neurons within the arcuate nucleus that project to melanocortin receptor neurons in the paraventricular nucleus is involved in the sensation of

A) sedation.
B) fear.
C) aggression.
D) hunger.

Question 46

The enteric nervous system plays the most important role in mediating serotonergic effects on gut function. However, researchers originally thought that enterochromaffin cells played the most important role because

A) experiments with knockout mice suggested greater involvement of enterochromaffin cells.
B) of the sheer number of enterochromaffin cells in the gut.
C) of the high density of 5-HT in enterochromaffin cells.
D) enterochromaffin 5-HT is released directly into the bloodstream.

Question 47

Signaling between the gut 5-HT and the brain is supported by several studies, one of which showed that firing rate of vagal afferents from the gut was increased by administration

A) of a catecholamine reuptake inhibitor, but not by an SSRI.
B) of an SSRI, but not by a catecholamine reuptake inhibitor.
C) of PCPA, but not by a catecholamine reuptake inhibitor.
D) of MDMA, but not by a catecholamine reuptake inhibitor.

Question 48

Which type of aggression has not been observed in animals?

A) Premeditated aggression
B) Predatory aggression
C) Maternal aggression
D) Irritable aggression

Question 49

Describe the synthesis of serotonin and explain why tryptophan levels in the brain increase after consumption of a high-carbohydrate, low-protein meal.

Question 50

Explain the primary mechanism responsible for termination of serotonergic transmission and name an important class of drugs that acts on that mechanism.

Question 51

Describe the primary acute mechanism of action of MDMA. What experimental evidence would you cite to convince someone not to take repeated high doses of MDMA (ecstasy)?

Question 52

Name the major serotonin cell clusters in the brainstem and describe their projection pathways.

Question 53

Why are cats the subject of choice in studies of firing patterns of dorsal raphe nucleus neurons? Describe the changes in firing of serotonergic neurons in the DRN of cats during different behavioral states.

Question 54

Identify the two ways by which 5-HT_1A receptors exert their postsynaptic effects. List two kinds of evidence supporting a role for 5-HT_1A receptors in regulating anxiety.

Question 55

Explain what makes 5-HT₃ receptors different from other serotonin receptors. Identify one important therapeutic use of 5-HT₃ receptor antagonists.

Question 56

How does 5-HT, which travels to the arcuate nucleus from DRN and MRN projections, suppress appetite and affect an animal's food-seeking behavior?

Question 57

Explain how techniques of genetic engineering have contributed to our understanding of the behavioral and physiological functions of the serotonergic system.

Question 58

What are the three major approaches to the study of the relationship between 5-HT and aggression in humans? What have these approaches showed us about the link between 5-HT and aggression?

Question 59

Explain how researchers determined that the anxiety-regulating 5-HT1A receptors are postsynaptic. What was the role of the stria terminalis (BNST) in this determination?

Question 60

Where does gut serotonin come from, what triggers its release, and what is its function?