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Lecture 6

PSYB65H3 Lecture Notes - Lecture 6: Monoamine Oxidase, Mania, Reuptake

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Ted Petit

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PSYB65- Lecture 6
Psychiatric Disorders
Schizophrenia- most commonly associated with hallucinations and delusions; age of onset is
from early 20s to about 30; neuropsychological tests show that people with schizophrenia in
frontal lobe tests, as well as tests of memory (verbal or nonverbal), and most other
neuropsychological tests show that they are completely normal; do show enlarged ventricles,
and lighter brain weight; genetic studies- 1% of the population is schizophrenic, 10-15% of
immediate family is schizophrenic, dizygotic twins had 10-15% concordance, monozygotic twins
had 40-75% concordance; antihistamines had a calming effect on patients; the drugs that were
most effective were dopamine antagonists (reduce functional activity of dopamine), particularly
phenothiazine and within that class chlorpromazine being the most commonly used/effective;
these drugs blocked the receptor sites for the biogenic amines/monoamines such as
norepinephrine, dopamine, and serotonin; the ones that blocked dopamine receptors were the
most effective; dopamine stimulants such as amphetamines could do two things- cause
schizophrenic symptoms in completely normal individuals; no difference in the amount of
dopamine in the brains of schizophrenic patients from normal persons; the difference was in the
number of dopamine receptors (D4)
Mood Disorders
Depression and Mania
Early research was done again by mistake, they gave people blood pressure medication
(Aldomet was the primary one that was used) which caused people to get depressed; these
chemicals caused a reduction in the monoamines (biogenic amines), the big one was reserpine
which caused the monoamines to leak from the synaptic vesicles (not to be packaged very well);
Aldomet was found to reduce the synthesis of norepinephrine and also caused depression;
which all suggested that depression was caused by the reduction of monoamines; 20-25% of
patients have a reduction in 5HIAA (a metabolite of serotonin) which suggested that there was a
reduction in serotonin in depressed patients; they also found that serotonin itself, not just the
breakdown product, was reduced in the brains of suicide patients; the most effective chemicals
were the tricyclic antidepressants (most recently tetracyclic) which all block serotonin,
norepinephrine reuptake; both of them had an increase in serotonin and norepinephrine, but
had very little to do with dopamine; thus, it is believed that dopamine plays very little role at all
in depression, but does so in schizophrenia; tryptophan, is a precursor to serotonin, it increases
levels of serotonin and is also effective in getting rid of depression; monoamine oxidase (MAO)
is the chemical that destroys the monoamines in the cell when chemicals are floating around
that are not packaged up; monoamine oxidase inhibitors prevent this from happening, and leads
to more monoamines and increases the activity of the system; basically, treatment of
depression relies on the increase of levels of monoamines particularly serotonin and
norepinephrine; problem with it or the mystery is that the drugs work within a few hours, but it
takes much longer (8 days) for the person to come out of the depression
Mania is an unrealistic, great feeling; usually treated immediately with some sort of
antipsychotic; not really well known how it works because antipsychotics are usually dopamine
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