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kyleannkelsey
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All cell bodies/Soma for serotonergic neurons are in the:
Hindbrain region: pons and medulla in a series of nuclei along the midline called the Raphe nuclei
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Serotonergic neurons Enter what brain parts:
- Midbrain, limbic structures (hypothalamus and hippocampus), cerebral cortex (cortical and subcortical innervations)
- down the spinal chord = regulate information processing and pain perception
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5HT3 receptor is what type of receptor
Ligand gated ion channel = excitatory receptor expressed in the brain
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All seratonin receptors except 5HT3 are what type?
G-protein
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“off” switch for serotonin transmission:
SERT
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Pre-synaptic seratonin receptor, local negative feedback:
5HT1a autoreceptor and b
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SSRIs target SERT of 5HT1A or B?
5HT1A or B
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What can MAOIs treat?
Treat depression, OCD, ADHD, and to control appetite
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Amphetamine stimulates serotonin release be what action?
Depends on it binding to and being transported by the reuptake pump
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Seratonin reuptake pump is the target for what drugs?
TCAsa nd SSRIs
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Differences between the TCAs and SSRI.:
- SSRIs = relatively selective for the serotonin transporter, safer
- TCAs = block both serotonin and NE transporters
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SImilrities between the TCAs and SSRI.:
Same ceiling/efficacy
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iproniazid MOA:
MOAI - Blocked the reuptake of biogenic amines
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Why respirine taken off the market?
HTN treatment - caused profound depression/suicide b/c deleted biogenic amines
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Why is biogenic amine theory not correct?
- 1. Some antidepressants don’t block reuptake of biogenic amines and they’re not MAOI
- 2. biogenic amines elevated in the synaptic cleft 30 minutes after you take one
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Supersensitivity of receptors in the brain leads to depression?
Yes
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chronic antidepressant treatment affects what receptors?
HHT, alpha 1 adrenergic and B-adrenergic
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Action of 5HT1A:
hyperpolarizes the membrane
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Action of SSRIs after first dose on neural firing:
- Inhibit SERT
- 5-HT1A:
- increases 5-HT1A and decreases rate of firing
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Action of SSRIs after chronic dose on neural firing:
- 2-4 wks:
- normalizes: raphe 5-HT neuron activity
- downregulation of 5-HT1A receptors
- elevate serotonergic transmission - unimpeded
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Cell bodies for NE neurons in the brain are in the:
BRAIN STEM’S Locus Ceruleus - blue body
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NE neurons send their projections:
- In the descending manner to the spinal cord
- Ascending manner to the forebrain structures (limbic: hypothalamus and hippocampus) and cerebral cortex
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Post-synaptic noradrenergic receptors:
Alpha adrenergic or beta adrenergic receptors
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Pre-synaptic noradrenergic receptors:
Alpha-2 adrenergic receptor
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DA cell bodies are located:
Midbrain: VTA or Substantia nigra
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Nigrostratal tract
Substantia nigra to the striatum = Parkinson’s disease
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Mesolimbic dopamine pathway
VTA to limbic structures = nucleus accumbens and the amygdala (reward circuitry pathway)
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Meso-Cortical dopamine pathway
VTA to the cerebral cortex = Regulates/contributes to thoughts = target for antipsychotic drugs
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Dopamine cell bodies Project to:
Limbic structures as well as the cerebral cortex
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5 different post-synapatic dopamine receptor subtypes, what type of receptor are they:
All G-protein coupled receptors
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VTA and Substantia nigra dopamine cell bodies = what are the somato-dendritic auto-receptors - inhibit the firing rate?
D2 dopamine receptors - coupled to K+ channels
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Opioids bind mu opiod receptors on:
- GABAergic interneurons in the VTA
- Leads to Release dopamine in the nucleus accumbens = rewarding or pleasurable experience
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Psychostimulant like cocaine or an amphetamine affects what receptors?
Inhibits the dopamine transporter, DAT
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Cholinergic pathway that goes to the hippocampus = very important for:
Short-term memory
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Block muscarinic receptors at hippocampus = difficulty with:
Short-term memory
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Where are Ach neuron cell bodies located and where do they proect to?
BMSI nucleus sends cholinergic projections to the cerebral cortex- Alzheimer’s
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(True/False) Muscarinic and nicotinic cholinergic receptors are important for brain function.
True – mediate reward of nicotine
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Desipramine has a little bit of selectivity for :
NE over serotonin
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Metabolite of imipramine is:
Desipramine = both are biologically active TCAs.
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Mechanism of action of TCAs:
inhibit the reuptake of NE and serotonin
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TCAs can produce sedation, related to their:
alpha-1 adrenergic receptor affinity
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TCA cardiac toxicity is related to what feature?
Ion channel blockade
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TCA adverse effect: Atropine-like side effects: dry mouth, constipation, blurred vision, mydriasis, metallic taste, urine retention is related to what receptors?
muscarinic blockade
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TCA adverse effect: Orthostatic hypotension is related to what receptors?
a1-AR and possibly a2-AR blockade.
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TCA adverse effect: Drowsiness, sedation and weight gain is related to what receptors?
Histamine-receptor blockade
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Alternate receptor interaction of TCAs, put in order of most to least:
Amitrylptyline >Doxepin> Imipramine = Clomipramine
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SSRI most potent in blocking SERT:
Paroxetine (does not equate to efficacy)
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SSRI most selective for the SERT vs NET
Escitalopram (does not equate to efficacy)
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SSRI most potent against DAT:
- Sertraline
- (Not a high affinity blocker of DAT, but amongst the SSRIs, it has the highest affinity)
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SSRI most potent anticholinergic agent:
Paroxetine
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Potential Clinical Consequences of 5-HT Reuptake Blockade:
- Sexual dysfunction
- Impaired cognition (No more likely to impair cognition than a TCA)
- Antidepressant effect
- GI issues
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SSRI with highest rates of sexual dysfunction:
Paroxetine (Paxil)
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SSRI with worst side effects:
Paroxetine (Paxil)
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When there is non-compliance due to adverse effect, is it reasonable to switch to one SSRI to another?
Yes
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SSRI with a flat-dose response curve:
Escitalopram (Lexapro)
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Escitalopram (Lexapro) Potency of blocking 5-HT is comparable to:
sertraline
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SSRI NOT metabolized by CYP 3A4:
Escitalopram (Lexapro)
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SSRIs from activating to sedating:
Proxac – Zoloft – Escitalopram – Fuvoxamine – Paxil
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MOA Mirtazapine :
- ALPHA 2 ANTAGONIST:
- Doesn’t block serotonin or NE transport = increases vesicular release =Potentiation of NE transmission in the CNS
- BOTH BLOCK THE NEGATIVE FEEDBACK LOOP
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MOA Nefazodone:
- = congener of trazodone
- Same kind of profile as trazadone = some 5-HT2 blocking activity = ability to block serotonin transport = some ability to block norepinephrine transport
- Low efficacy
- BOTH BLOCK THE NEGATIVE FEEDBACK LOOP
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Why does Tyramine cause negative effects:
- Vasorepressor
- promotes the release of NE in the periphery
- Causes MABP surge in periphery
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Do MOAs produce adaptive changes in CNS similar to TCAs and SSRIs?
Yes
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Irreversible inhibitors of MAO-A and MAO-B:
(isocarboxazid and Phenelzine)
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reversible inhibitors of MAO-A and MAO-B:
(Tranylcypromine)
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BP effect of MOAIs:
May lower, not profound
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Describe Ketamine
- glutamate receptor antagonist
- N-methyl-D-Aspartate (NMDA) subtype of glutamate receptor
- IV
- Couple of hours = improvement in mood
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SJW effects what receptor types?
DA, 5HT, NE, GABA, Glutamte – all with low potency
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Molecular mechanism of action of HYPERFORIN:
- REDUCE THE SODIUM GRADIENT
- -not competitive inhibitor
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Hyperforin or hypericin cross the BB well?
Hyperforin
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GI distrubance = very high with fluoxetine, BUT almost non-existant in:
St. John’s Wort
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Adverse effects of SJW:
- Photosensitivity
- Serotonin Syndrome
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MOA of Lithium:
- alter the coupling of receptors with G-proteins.
- Inhibits breakdown of IP2 to IP1
- depletion of DAG and IP3 and ¯ [Ca2+]
- - not really selective
- Activates phospholipase C
- disrupts glycogen synthase/adenylyl cyclase activity
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