Exam 2 - Catecholamines Flashcards
The rate-limiting enzyme in the synthesis of catecholamines is:
tyrosine hydroxylase
What is the synthesis of catecholamines?
tyrosine, need tyrosine hydroxylase -> DOPA, needs AADC -> Dopamine, needs dopamine betahydroxylase -> norepinephrine
6-hyroxydopamine is a ________ used to ________.
neurotoxin, damage catecholamine neurons
Catecholamines
include dopamine, norepinephrine, and epinephrine
What transporter is responsible for the reuptake of catecholamines? What are the two types?
- vesicular monoamine transporter (VMAT)
- VMAT 1 and VMAT 2
Resperine
- blocks reuptake of dopamine, blocks VMAT
- lowers BP and has a sedative effect
What does the release of catecholamines cause?
an increase of locomotor activity
What does inactivation of catecholamines depend on?
1) reuptake by dopamine transporter and norepi. transporter
2) metabolic breakdown by enzymes COMT and MAO
What does the breakdown of catecholamines by COMT and MAO cause?
- dopamine gets turned into HVA
- norepi gets turned into MHPG and VMA
What is the nigrostriatal pathway?
- originates in substantia nigra and goes to the caudate-putamen
- play an important role in the control of movement
- this pathway is damaged in parkinson’s disease
Parkinson’s disease
- neurodegenerative disease
- occurs when the cells that produce dopamine (in substantia nigra) die
- no cure; L-dopa can be offered to replace dopamine; inhibition of dopamine metabolism by MAO type B inhibitors; anticholinergics that block ACH to prevent tremors; surgery
What are the symptoms of Parkinsons?
- M - muscle rigidity
- I - impaired balance
- S - slowness and stiffness
- T - (resting) tremors
MPTP
- neurotoxin that causes symptoms of parkinsons
- causes a loss of neurons in the substantia nigra
Mesolimbic system
- originates in the ventral tegmental area and travels to the nucleus accumbens
- important in addiction
Mesocortical system
- originates in ventral tegmental area and projects to the cerebral cortex
- important in addiction
Explain Olds and Milners experiment
- identified the certain brain sites where direct electrical stimulation is reinforcing
Dopamine receptors
- metabotropic
- D1 to D5
What is the difference between the D1 and D2 receptors?
- D1 increased CAMP synthesis
- D2 decreased CAMP synthesis
What are the dopamine agonists? What receptor do they affect?
- apomorphine - D1 and D2
- SKF 38393 - D1
- quinpirole - D2 and D3
- agonists cause an increase in activity, also caused by giving 6-OHDA
Dopamine antagonists ________ locomotion. What is an example of a dopamine antagonist? What does high doses of this antagonist do?
- decrease
- haloperidol
- catalepsy (waxy flexbility)
Noradrenergic system
- originates in the locus coeruleus and provides input to the cortex, limbic system, thalamus, and hypothalamus
What is the role of the locus coeruleus?
vigilance/arousal
Adrenergic receptors, what are the two subtypes? Which inhibit and enhance the release of CAMP?
- metabotropic
- alpha and beta
- beta receptors enhance the synthesis of CAMP
- alpha receptors inhibit the rate of CAMP
Adrenergic agonists _________ arousal and eating behavior.
stimulate/increase
Where are the neural mechanisms for eating located? What is responsible for responses in this area?
- hippocampus, specifically the paraventricular nucleus
- alpha 2 receptors
What effect does norepi. have on eating?
- induces eating
