Catecholamines Flashcards
The enzyme required for Tyrosine—–>DOPA??.
Tyrosine hydroxylase.
The enzyme required to convert DOPA—->Dopamine??.
Aromatic amino acid decarboxylase(AADC).
The enzyme to convert dopamine—–>Norepinephrine??
Dopamine B-hydroxylase.
Packaging of catecholamines?
- Achieved via Vesicular monoamine transporter(VMAT).
- released via exocytosis.
Functions of;
- Amphetamines?
- Reserpine?
Amphetamines:
- increase cell firing.
Reserpine:
-
Block DA uptake in VMAT2,
- results in depression and sedation.
- The function of Autoreceptor D2 autoreceptors?
How does it achieve this function?
what type of autoreceptor are they?
Overall function: inhibits catecholamine release.
- Enhances opening of K+ channels, hyperpolarisation.
therefore:
- reduces AP and Ca2+ influx.
- Somatodendritic autoreceptor.
The function of transporter proteins?
- Allow the reuptake of NE and DA.
Role of Tricyclic antidepressants?
- Inhibit reuptake of both NE and Serotonin.
Neurophysiology of cocaine?
- inhibits the reuptake of all mono-amine transmitters:
DA,5-HT, and NE.
Function of Roboxetine( edronax)?
Function of Atomexetine(Strattera)?
- Roboxetine : antidepressant, blocking NE transporters(reuptake)
-
Atomoxetine (Strattera):
- Used for ADHD to block NE transporters.
The difference in function between Catechol-O-methyltransferase(COMT) AND Monoamine oxidase(MAO)??
COMT: degrades and breakdown dopamine.
MAO: degrade and breakdown of NE.
Metabolites of DA and NE??
- DA: Homovanillic acid.
- NE: CNS: MHPG and PNS: VMA.
How can levels of catecholamine levels be measured?
- Measuring the levels of metabolites within urine, e.g. Homovanillic acid for DA.
Function of Phenelzine(Nardil) and Tranylcypromine(Parnate)?
- Are MAO inhibitors, which inhibit metabolism and breakdown of NE.
Function of Entacapone(Comtan) and Tolcapone(Tasmar)?
- inhibition of COMT, inhibits breakdown of DA.
Enhances the functioning of L-DOPA for PD.
Describe the Nigrostriatal pathway:
- from where—where?
- Cell groups?
- Substantia nigra———-
–>Striatum.
or
–>caudate putamen.
A9 CELL GROUP.
Describe the mesolimbic dopamine pathway;
Cell groups and projections?
- A10 cell group.
-
VTA——-
- –> limbic system( Nucleus accumbens and Olfactory tubercules).
Describe the mesocortical dopamine pathway.
- Cell group and projections?.
- A10 cell group.
- VTA——–>
- –>prefrontal cortex.
State the significance of the nigrostriatal pathway to PD models?
toxins used as a model for PD?
- Fascilitates voluntary movement.
- PD involves the loss of DA neurons from the SN, which leads to denervation of the striatum.
Neurotoxins:
- 6-OHDA and MPTP: damage the nigrostriatal pathway.
State the type of receptor DA receptors are.
- Briefly state the mechanism in activation of these receptors?
- State the receptors within D1-like receptors and D2-like receptors.
Metabotropic receptors:
- interacting with G-proteins and function as secondary messengers.
D1-like receptors: D1 and D5.
D2-like receptors: D2-D4.
Activation of:
D1 receptors and D2 receptors?
D1 receptors:
- stimulates adenylyl cyclase and synthesis of cAMP.
D2 receptors:
- inhibits adenylyl cyclase and synthesis of cAMP.
- Opening of K+ channels, as activation of G-protein enhances K+ opening.
Mice knockout:
D1 knockout?
D2 knockout?
Both knockout?
D4 knockout?
- D1 receptor knockout: deficits in cognitive tasks.
- D2 receptor knockout: impairment in spontaneous movement, coordination, and posture.
Both: leading to fatality in the 2nd and 3rd week of life.
- D4 receptor knockout: hypersensitive to cocaine and methamphetamines.
Quick overview of the drugs.
Describe the Locus Coerulus(LC) in pons:
- Group of cells?
- Projections?
- A6 cell group.
- Projections from pons to——-
—> all areas of the forebrain.
—> cerebellum and spinal cord.
