Parkinsons/Psychosis Flashcards
How much neuron loss usually occurs before Parkinsons symptoms show?
80%
What is the direct pathway of the basal ganglia?
Thalamus -> association cortex -> striatum -> D1 direct to globus pallidus internal + substantia nigra reticulata -> VA/VL of thalamus -> premotor cortex
What is the indirect pathway of the basal ganglia?
frontal cortex-> striatum -> GPe -> STN
Which basal ganglia pathway predominates in Parksinsons disease?
Indirect
What is a likely cause of tremor?
Reduced DA resulting in increased Ach excitation
What are the 5 DA pathways of the brain?
Nigrostriatal Mesolimbic Mesocortical Median eminence Chemoreceptor trigger zone
What are the two enzymes which may break down DA?
monoamine oxidase and Catechol-O-methyltransferase
What is the effect of carbidopa?
inhibit peripheral metabolism of levodopa, allow more L-dopa to cross BBB
Which enzyme does carbidopa inhibit?
DOPA decarboxylase
What is selegiline?
selective irreversible MAO-B inhibitor
What determines if a cell is noradrenalinergic or dopaminergic?
Presence of dopamine beta hydroxylase converts DA to NA and it is therefore a NA cell
Which drug blocks the Catechol-O-methyltransferase dopamine pathway?
Entacapone
How can Parkinsons treatment be monitored?
Plasma levels of prolactin are easy to monitor
When and why does successful Parkinsons treatment stop working?
After 2-10 years, probably because of huge neuronal death
Why is postural hypotension a side effect of LDOPA?
Extra DA is made in NA neurons, so NA levels may be reduced therefore blood pressure reduces
Where and what is the chemoreceptor trigger zone?
An area of medulla oblongata that receives inputs from blood-borne drugs or hormones, and communicates with other structures in the vomiting center to initiate vomiting.
What is the effect of high LDOPA in the peripheral blood?
Activation of the CTZ and nausea
What is the word for a drug designed to counteract side effects?
adjunct
Does carbidopa cross the BBB?
No
What drug can be used to block nauseous effects of Parkinsons treatment?
Domperidone (D2 R antagonis)
It does not cross BBB, so blocks DA action only outside CNS eg at CTZ to reduce DA nauseous effects
When is Benzhexol used?
This can be used to stop tremor in parkinsons, as a muscarinic Ach antagonist (atropine like effects)
This is only prescribed for drug-induced Parkinsons (younger) because ACh block in brain can increase dementia risk
What is Risperidone?
antipsychotic partial agonist of 5HT 1A, antagonist of 5HT 2A and D2
What is EPS?
extrapyramidal symptoms eg dystonia, parkinsonia
