serotonin

Question 1

5-HT is an extremely important neurotransmitter that
influences many physiological and behavioral processes… and
is also the target of many drugs

Answer 1

• Fluoxetine (Prozac) and other medications
  exert their therapeutic effect by acting on
  serotonin system;
• Hallucinogenic drugs such as LSD,
  psilocybin, MDMA and others mimic
  some of the effects of serotonin;
• Many ”normal” behaviors appear to
  depend on intact serotonin function in the brain

Question 2

where is 5-HT located

Answer 2

The vast majority of 5-HT is peripheral  gut

Question 3

Peripheral 5-HT controls

Answer 3

gut motility and initiates peristaltic and secretory reflex

Question 4

Disruptions of brain 5-HT function are
thought to play a significant role in
various psychiatric conditions such as:

Answer 4

Anxiety, substance use & addiction,
mood control, et

Question 5

Tryptophan

Answer 5

is an essential amino acid, which
means it cannot be synthesized by the
organism. It, therefore, must be obtained via
diet.

Question 6

Foods that are high in tryptophan:

Answer 6

Oats, bananas, dried dates, milk, yogurt, cottage
cheese, red meat, eggs, fish, poultry, sesame,
chickpeas, sunflower seeds, pumpkin seeds,
peanuts, etc

Question 7

Tryptophan Hydroxylase

Answer 7

is
the rate-limiting enzyme in serotonin
synthesis

Question 8

Tryptophan must compete with large, neutral amino
acids to cross the BBB

Answer 8

High-protein, low carbohydrate diet does not increase
brain tryptophan  too much competition;
- High-carbohydrate, low-protein diet does enhance brain
levels of tryptophan, and ultimately synthesis of 5-HT

Question 9

Rate-limiting step

Answer 9

of central 5-HT synthesis is
passage of tryptophan across BBB

Question 10

Tryptophan hydroxylase comes in 2
forms (at the level of the gene):

Answer 10

1. TPH1 – expressed by 5-HT
   secreting cells in the gut and
   melatonin-secreting cells in the
   pineal gland;
2. TPH2 – expressed by 5-HT
   secreting neurons

Question 11

Tryptophan hydroxylase is
present only in

Answer 11

a small subset of neurons

Question 12

Raphe
Nuclei.

Answer 12

Tryptophan hydroxylase is
present only in a small
subset of neurons;
These cells are located in a
series of cell groups in the
brainstem, collectively
known has the Raphe
Nuclei

Question 13

Almost all serotonergic neurons in the CNS are found along the
midline of the brainstem, associated with the

Answer 13

raphe nuclei

Question 14

Raphe nuclei are divided into

Answer 14

dorsal and median raphe nuclei

Question 15

Serotonin receptors are a large group of G protein coupled receptor (mostly) and ligand-
gated ion channels found in both the

Answer 15

brain and periphery

Question 16

5-HT1A

Answer 16

receptors are concentrated
in the hippocampus, septal area,
amygdala, and the dorsal raphe
nuclei

• Reduce cAMP synthesis by
  inhibiting adenylyl cyclase;
• Increase opening of K+ channels
  and membrane hyperpolarization.
• Similar activity to D2 and a2
  receptors;
• Leads to decrease cell firing in post-
  synaptic cell (post-synaptic receptor)
  or serotonergic neuron itself (auto-
  receptor

Question 17

5-HT2A

Answer 17

receptors are located
throughout the brain, however they
are in large numbers in the
(neo)cortex

Primarily responsible for activating
phosphoinositide 2nd messenger
system.
- Increases Ca2+ influx into
postsynaptic cells;
- Activated protein kinase C (PKC)

Question 18

Following the release of 5-HT, it is rapidly removed from
the synaptic cleft via the

Answer 18

5-HT reuptake transporter
(SERT)

Question 19

What happens when we don’t have
enough tryptophan?

Answer 19

SAD

Question 20

SAD is thought to be caused by

Answer 20

a reduction in sunlight and
may be related to reductions in serotonin (although, nothing
has been proven… yet). Typical SSRI’s can reverse
depressive-like symptoms of SAD.

Question 21

The Atkins diet

Answer 21

a commercial weight-loss
program that essentially limits (severely)
the amount of carbohydrates one
consumes.

Question 22

We know, however, that low levels of
central serotonin are strongly associated
with levels of

Answer 22

depression