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- author "Amon"
- tags "PSYCHOSIS "
- description "CHAPTER 9 PSYCHOPHARMACOLOGY"
- fileName "Ch.9 Psychosis & Schizophrenia"
- freezingBlueDBID -1.0
- Clinical description of psychosis
- Psychosis is a syndrome (mixture of symptoms) that can be associated with many different psychiatric disorders
Minimum definition of psychosis
Delusions and hallucinations
Schizophrenia positive symptoms
delusions, hallucinations disorganized speech, disorganized behavior, catatonic behavior, agitation, distortions in language
Negative symptoms of schizophrenia
apathy, anhedonia, avolition, asociality, alogia, affective blunting and others
what are prodromal symptoms?
Negative symptoms that occur before the onset of the full syndrome.
What are the key negative symptoms identified solely on observation of the patient
reduced speech, poor grooming, limited eye contact.
what are some negative symptoms identified with some questioning
reduced emotional responsiveness, reduced interest, reduced social drive.
What are the five symptom-dimensions of schizophrenia?
Positive, negative, aggressive, cognitive, and affective symptoms.
what regions of the brain are the positive symptoms of schizophrenia localized to?
Malfunctioning Mesolimbic circuits, specially the nucleus accumbens
What regions of the brain are associated with negative symptoms
malfunctioning mesocortical circuits
What regions of the brain are associated with affective symptoms
What regions of the brain are associated with cognitive symptoms?
what regions of the brain are associated with aggressive and impulsive symptoms?
the orbitofrontal cortex
What neurotransmitter is most closely associated with the positive symptoms of schizophrenia?
How is DA synthesized?
- from amino acid Tyrosine, taken up into the neuron by a tyrosine pump or transporter
- -Tyrosine is converted to Dopa by enzyme tyrosine-hydroxylase (TOH),
- -then to DA by the enzyme dopa decarboxylase (DDC)
- -then taken up into synaptic vesicles by a vesicular monoamine transporter (VMAT2) and stored until used.
How is DA terminated?
- -By reuptake pump called DAT
- -by enzyme MAO -A inside the neuron
- -by MAO-B
- -by enzyme catechol-O-methyl transferase (COMT)
Which DA receptor has been the most extensively studied
What happens when there is occupancy of DA or DA antagonists on the DA2 autoreceptor?
Negative feedback input or a braking action on the release of DA from the neuron
How many DA pathways have been discovered in the brain so far?
5 DA pathways
What are the 4 well-known DA pathways?
- -The mesolimbic dopamine pathway
- -the mesocortical DA pathway
- -the nigrostriatal DA pathway
- -the tuberoinfundibular DA pathway
what is the route of the mesolimbic pathway
it projects from ventral tegmental area in the brainstem to the nucleus accumbens in the ventral striatum
What is the route of the mesocortical DA pathway?
It projects from the ventral tegmental area to the PFC (specifically to DLPFC)
what is the route of the nigrostriatal DA pathway?
It projects from the substantia nigra to the basal ganglia or striatum
What is the route of the tuberoinfundibular DA pathway?
it projects from the hypothalamus to the anterior pituitary gland
Which DA pathway is involved with positive symptoms of schizophrenia?
Mesolimbic DA pathway
Which DA pathway is involved with negative, cognitive and affective symptoms of schizophrenia?
Mesocortical DA pathways
What is the mechanism of action for drugs that treat the positive symptoms of schizophrenia?
Drugs are blockers of D2, DA receptor
Hypothetically what accounts for the positive symptoms of schizophrenia?
Hyperactivity of the mesolimbic DA pathway
Hypothetically what may be the reason for the negative symptoms of schizophrenia
deficit of DA activity in the mesocortical projections to the DLPFC
theoretically what would happen if DA is increased in the mesocortical DA pathway?
might improve negative, cognitive and affective symptoms of schizophrenia
what would be the effect of increasing DA in the mesolimbic DA pathway?
it would worsen the positive symptoms of schizophrenia
Conventional antipsychotics can produce a worsening of negative symptoms
how is the nigrostriatal DA pathway affected by decreasing DA?
it causes movement disorders, Parkinson's disease, akathisia (type of restlessness) dystonia (twisting movements) and tardive dyskinesia
What are some of the effects of treating patients with conventional antipsychotics on the tuberoinfundibular DA pathways
Prolactin levels rise, these causes galactorrhea (breasts secretions)amenorrhea (loss of ovulation) and sexual dysfunctions