Pharmacology > Serotonin and Dopamine > Flashcards

Serotonin and Dopamine Flashcards

(22 cards)

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1
Q

Describe the major features of serotonin and dopamine neurotransmission.

A

SEROTONIN
1. L-tryptophan => 5-HTP via tryptophan hydroxylase RLE
=> tryptophan is NOT synthesized by the body; essential AA
=> TH is not normally saturated, thus increasing dietary intake of tryptophan can increase 5-HTP production
=> 5-HTP is an OTC nutraceutical used to treat depression
2. 5-HTP => serotonin
3. serotonin => 5-HIAA (inactive excreted metabolite)

DOPAMINE

  1. tyrosine => L-DOPA via tyrosine hydroxylase RLE
  2. L-DOPA => dopamine via dopamine decarboxylase
    * dopamine canNOT cross BBB*
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2
Q

Describe how tryptophan manipulations are thought to affect brain function.

A
  • requires appropriate ratio of W to other AAs b/c W competes with other neutral AAs to cross the BBB
  • common foods = whole milk, dried prunes, semi-sweet chocolate
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3
Q

Where on the neurons are each 5-HT1 receptor found?

A

5-HT1a

  • found on both pre- and post-synaptic
  • on the pre-synaptic neuron, it is found on the soma/dendrites to act as an autoreceptor to limit AP generation
  • on the post-synaptic neuron, it is found on the synaptic membrane to receive signals

5-HT1b

  • found on both pre- and post-synaptic
  • pre-synaptic receptors are found on the axon terminal to inhibit phosphorylation of calcium channels (no cAMP => no PKA) => inhibits serotonin release

5-HT1d
- only found on post-synaptic neurons

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4
Q

Describe the following for each serotonin receptor family

  • MOA
  • location on the neuron
A

5-HT1a, b, d

  • MOA => Gi => inhibits NT release and activates K channels
  • 1a = presynaptic cell body and postsynaptic membrane
  • 1b = presynaptic nerve terminal and postsynaptic membrane
  • 1d = postsynaptic only

5-HT2a, b, c

  • MOA = Gq => PLC => IP3/DAG => Ca2+
  • post-synaptic

5-HT3

  • MOA = ligand gated cation influx when activated by SE
  • post-synaptic

5-HT4

  • MOA = Gas => cAMP => PKA
  • post-synaptic
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5
Q

Describe the following for each serotonin receptor family:

  • location in the body
  • effects
A

5-HT1a

  • cortex, hypothalamus => mood and cognitive function
  • Raphe nuclei => inhibit 5-HT release

5-HT1d
- cerebral VSM nerve terminal => inhibit NT release

5-HT2a/c

  • striatum => hallucinations
  • frontal cortex => inhibit DA release

5-HT3

  • enteric chromaffin cells => gut motility
  • area postrema/esmetic center => N/V

5-HT4
- myenteric plexus => gut motility

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6
Q

What is the role of the 5-HT transporter?

A

reuptake of 5-HT from the nerve terminal

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7
Q

Describe the following for buspirone:

  • MOA
  • effects
  • use
  • side effects
A

MOA
- partial agonist for 5-HT1a receptors located on the post-synaptic receptors in the cortex

EFFECTS
- INHIBIT the INHIBITORY activity of 5-HT1 => ACTIVATE serotonin release => more endogenous serotonin

USE

  • GAD
  • depression (when used in conjunction with SSRIs)

SIDE EFFECTS

  • anxiety, drowsiness, nausea
  • associated with initial suppression of endogenous serotonin release before the receptor has become desensitized
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8
Q

Describe the following for sumatriptan:

  • MOA
  • effects
  • use
  • side effects
  • contraindications
A

MOA
- 5-HT1d agonist

EFFECTS

  • inhibits release of nociceptive and inflammatory NTs (CGRP, NKA, and substance P)
  • activates MLCK => cerebrovascular vasoconstriction

USE
- migraines

SIDE EFFECTS
- cerebrovascular vasoconstriction

CONTRAINDICATIONS
- coronary artery disease

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9
Q

Describe the following for the use of SSRIs:

  • MOA
  • effects
  • use
  • side effects
  • contraindications
  • prototype drugs
A

MOA
- prevent reuptake at the axon terminal

EFFECTS

  1. reuptake inhibition causes an increase in serotonin in the presynaptic cleft
  2. initially, there is continued inhibition of the post-synaptic serotonin producing neuron because of continued activation of 5-HT1a inhibition
  3. 2-4 weeks later (time it takes for anti-depressants to start working, there has been a downregulation of 5-HT1a because of all the serotonin activation
  4. less 5-HT1a receptors => less inhibition => more serotonin release => antidepressive effects

USE

  • depression
  • anxiety from PTSD, OCD

SIDE EFFECTS

  • sexual dysfunction
  • insomnia
  • due to enhanced activation of other receptors

CONTRAINDICATIONS

  • pts taking MAOIs => enhance effects of serotonin since it is not being broken down to its inactive metabolite 5-HIAA
  • can lead to serotonin-syndrome (hyperthermia, muscle tremors, twitching, agitation, arrhythmia, seizure)

PROTOTYPE DRUGS

  • fluoxetine
  • sertraline
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10
Q

Describe the following for the therapeutic use of SARIs:

  • MOA
  • effects
  • use
  • side effects
  • contraindications
  • prototype drugs.
A

MOA

  • blocks serotonin reuptake
  • blocks 5-HT2a and 5-HT2c

EFFECTS

  • increased serotonin in the synapse => increased production and release of serotonin
  • block 5-HT2a => block alertness
  • block 5-HT2c => block sexual behavior and anxiety

USE

  • depression (rarely used for this anymore; in combination with SSRIs)
  • anxiety
  • insomnia w/o depression

SIDE EFFECTS
- drowsiness

CONTRAINDICATIONS
- black box warning for suicidality in young adults

DRUG
- trazadone

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11
Q

Describe the following for risperidone:

  • MOA
  • effects
  • use
  • side effects
A

MOA

  • 5-HT2a antagonist
  • blocks D2 and D3

EFFECTS

  • reduces DA release in mesolimbic (too high in psychosis)
  • increases DA release in mesocortical (too low in psychosis)

USE

  • anti-psychotic
  • schizophrenia
  • manic episodes of bipolar disorder

SIDE EFFECTS

  • weight gain
  • akathisia (constant need to move)
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12
Q

Describe the following for ondansetron:

  • MOA
  • effects
  • use
  • side effects
  • notes
A

MOA
- 5-HT3 antagonist

EFFECTS
- block 5-HT3 => block serotonin release on vagal afferents => block activation of area postrema and emetic center => inhibit N/V

USE
- prevent N/V in chemotherapy patients

SIDE EFFECTS

  • few
  • well tolerated

NOTES

  • 90% of serotonin release occurs in the gut from the enterochromaffin cells
  • acts on vagal efferents to induce N/V in response to detection of a toxin in the gut
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13
Q

Describe the following for metoclopramide:

  • MOA
  • effects
  • use
  • side effects
  • notes
A

MOA

  • dopamine antagonist
  • 5-HT4 agonist

EFFECTS
- promotes gastric motility by increases activity of IPAN

USE
- short term stimulation of gastric motility in diabetics and post-surgical patients

SIDE EFFECTS
- dopamine agonist effects

NOTES
- 5-HT4 => serotonin => intrinsic primary afferent neurons (IPAN) => ACh => longitudinal and circular gut muscles

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14
Q

List the 4 dopaminergic pathways. Indicate where excess/deficit dopamine occurs and what conditions it can lead to.

A
  1. mesolimbic (VTA to limbic)
    => excess DA leads to psychosis
  2. mesocortical (VTA to prefrontal cortex)
    => deficit DA leads to schizophrenia and lack of motivation
  3. tuberoinfundibular pathway (arcuate nucleus of hypothalamus to median eminence of the pituitary)
    => deficit DA leads to parkinson’s
  4. chemotrigger zone (brainstem)
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15
Q

Describe the MOA and members of the D1 receptor family.

A

MOA
- Gas => cAMP => increase DA release

FAMILY

  • D1 = frontal cortex, arcuate nucleus, hypothalamus
  • D5 = hypothalamus, striatum

ACTIONS
- renal and splanchnic vasodilation

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16
Q

Describe the MOA and members of the D2 receptor family.

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A

MOA

  • Gi => decreased cAMP
  • activates K channels
  • decreased voltage gated Ca channels

FAMILY

  • D2 = striatum, pit
  • D3 = VTA
  • D4 = hypo, amygdala, hippo
17
Q

Describe the following for the therapeutic use of L-DOPA:

  • MOA
  • effects
  • use
  • side effects
  • adjunctive therapy
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A

MOA
- precursor loading

EFFECTS

  • increased synthesis of dopamine, norepinephrine, epinephrine in the CNS and PNS
  • crosses BBB

USE
- parkinson’s

SIDE EFFECTS
- limbic = hallucinations
- dyskinesia
can be alleviated with reduced doses and cocktail drugs

ADJUNCTIVE THERAPY

  • carbidopa blocks dopamine carboxylase to prevent L-DOPA => dopamine
  • cannot cross BBB so reduces toxic side effects in the periphery to allow more L-DOPA to enter the brain rather than be metabolized in the gut
18
Q

Describe the following for bromocriptine:

  • MOA
  • effects
  • use
  • side effects
Study These Flashcards
A

MOA
- D2 receptor agonist in basal ganglia

EFFECTS

  • reduces oxidative damage in dopaminergic cells
  • increased dopamine in system

USE
- parkinson’s

SIDE EFFECTS

  • valvular fibrosis with long-term use
  • decreased impulse control leading to atypical risky behaviors
19
Q

Describe the following for selegiline:

  • MOA
  • effects
  • use
  • side effects
  • notes
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A

MOA
- MAO-b inhibitor

EFFECTS
- selective for one type of MAO

USE

  • parkinson’s (low dose)
  • depression (high dose)

SIDE EFFECTS

  • dizziness due to hypotension (low dose)
  • hypertension and serotonin syndrome (high dose)
  • dry mouth due to increased sympathetic activity

NOTES

  • doesn’t require strict monitoring of dietary tyramine since it is selective
  • but should be mindful at higher doses
20
Q

Describe the following for tolcapone:

  • MOA
  • effects
  • use
  • side effects
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A

MOA
- COMT inhibitor

EFFECTS

  • prolongs L-DOPA half-life
  • decreases “off time”
  • able to reduce dose needed of L-DOPA

USE
- parkinson’s in conjunction with L-DOPA

SIDE EFFECTS

  • oscillations in motor function due to off time
  • excess dopamine effects: dyskinesia, hallucinations, nausa
21
Q

Describe the following for haloperidol:

  • MOA
  • use
  • side effects
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A

MOA
- D2 receptor antagonist => increases DA

USE
- antipsychotics

SIDE EFFECTS

  • extra motor movement
  • akathisia, tics
22
Q

Describe the following for methylphenidate: (RECALL)

  • MOA
  • effects
  • use
  • side effects
Study These Flashcards
A

MOA
- DE and NE reuptake inhibitor

USE
- ADHD

SIDE EFFECTS
- tachycardia

CONTRAINDICATIONS

  • arrhythmia
  • HTN
  • TCAs (further exacerbate concentrations of catecholamines)
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