Schizophrenia Flashcards
(29 cards)
how is dopamine made
from amino acids (particularly tyrosine)
- tyrosine transporter transports tyrosine from bloodstream to neuron
- tyrosine hydroxylase (TOH) is enzyme that converts tyrosine to DOPA
- DOPA decarboxylase converts DOPA to dopamine (DA)
where does dopamine bind
to 5 types of postsynaptic receptors (D1-D5)
D2 = most significant because it acts as a negative feedback mechanism regulating release of dopamine from pre-synaptic neurone
3 enzymes involved in the break down of dopamine and it’s final breakdown product
- MAO, aldehyde dehydrogenase and COMT
Final product - homovanillic acid (HVA)
role of mesolimbic pathway
perception
addiction
pleasure and reward seeking behaviours
emotions
mesolimbic effect in psychotic symptoms
hyperactivity of of dopamine = positive psychotic symptoms
ideal drug action in mesolimbic pathway to treat psychosis
decrease DA
antagonism of D2 receptors
SE = reduction of pleasure effects
complete blockade = neurolepsis
role of mesocortical pathway
cognition Attention memory emotional behaviour learning
mesocortical effect in psychotic symptoms
decreased dopamine = negative and depressive symptoms
ideal drug action in mesocortical pathway to treat psychosis
increase DA to treat -ve and cognitive symptoms
role of nigrostriatal pathway
movement and sensory stimuli
hyperactivity of dopamine in nigrostriatal pathway
hyperkinetic movement disorders
tics, dyskinesia and chorea
Symptoms caused by blockade of D2 receptors in nigrostriatal pathway
akathisia
dystonia
parkinsonian symptoms
long-standing blockade = tardive dyskinesia
ideal drug action in nigrostriatal pathway to treat psychosis
leave dopaminergic tone unchanged
tuberoinfundibular pathway role
regulates prolactin secretion by the pituitary gland
4 major dopamine pathways in brain
mesolimbic
mesocortical
nigrostriatal
tuberoinfundibular
blockade of D2 receptors in tuberoinfundibular pathway
hyperprolactinaemia which clinically manifests as:
- sexual dysfunction
- glactorrhoea (abnormal lactation)
- amenorrhea (absence of menstruation)
- infertility
long-term = association with osteoporosis
ideal drug action in tuberoinfundibular pathway to treat psychosis
leave dopaminergic tone unchanged
ideal drug action of anti-psychotic on all 4 dopamine pathways
mesolimbic - decrease DA (to treat +ve symptoms)
mesocortical - increase DA (to treat -ve and cognitive symptoms)
nigrostriatal - no effect
tuberoinfundibular - no effect
side effects of muscarinic and cholinergic blocking antipsychotics
constipation
dry mouth
blurred vision
cognitive blunting
e.g. chlorpromazine
examples of extra-pyramidal symptoms
inability to sit still involuntary muscle contraction tremors stiff muscles involuntary facial movements
3 stages of treatment for schizophrenia
- Acute phase
- patient exhibits acute symptoms (+ve and -ve)
- normally starts in hospital
- patient is a danger to self and other - Stabilisation phase
- first 6 months after onset of acute phase
- start to reduce symptoms
- start antipsychotic - Stable phase
- remain on lowest effective dose to control symptoms
- aim to integrate patient back into society
negative symptoms of schizophrenia
loss of emotional connectedness slow down of movements lack of socialisation loss of speech lack of focus/engagement loss of executive functions
positive symptoms of schizophrenia
hallucinations agitation unusual behaviour delusions disorganised speech
3 considerations when treating schizophrenia
smoking - marijuana and tobacco induces CYP1A2 which metabolises clozapine (suddenly stopping = higher clozapine conc in body)
if pregnant - take antipsychotic patient has most experience with
side effects - constipation, drooling and heart inflammation
