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Four Roads for One Molecule: Mapping the Brain's Dopamine Pathways · Understanding the Brain

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  Speaker 1: Welcome back, everybody. Today we look at dopamine pathways and
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  Speaker 1: what EPPP candidates actually need to know. Dopamine pathways appear
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  Speaker 1: on the EPPP candidates sometimes make the material harder than
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  Speaker 1: it needs to be. You don't need to draw the
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  Speaker 1: brain from memory. Instead, remember four connections. Mesolimbic, mesocortical, nigrostriatal,
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  Speaker 1: and tuberinfedibular. Mesolimbic means positive psychotic symptoms. Mesocortical is negative
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  Speaker 1: and cognitive symptoms. Nigrostriatal is movement. And tuberinfedibular is prolactin.
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  Speaker 1: So mesolimbic is too much dopamine. The mesolimbic pathway is
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  Speaker 1: strongly associated with reward, motivation, reinforcement, and salience. For EPPP,
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  Speaker 1: the key association is positive symptoms of schizophrenia, hallucinations, and delusions.
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  Speaker 1: The traditional dopamine hypothesis proposes that excessive dopamine activity in
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  Speaker 1: the mesolimbic pathway contributes to positive psychotic symptoms. Imagine a
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  Speaker 1: patient who hears threatening voices and believes government agents have
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  Speaker 1: installed surveillance. Again, positive symptoms, increased mesolimbic dopamine activity, antipsychotic
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  Speaker 1: medications block the deep dopamine D2 receptors, can therefore reduce
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  Speaker 1: these symptoms. Mesocortical pathways, too little dopamine, which is associated
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  Speaker 1: with cognition, motivation, emotion, and executive functioning. Here you're looking
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  Speaker 1: at the negative symptoms, so reduced motivation, reduced speech, social withdrawal,
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  Speaker 1: flat or diminished emotional expression. So you're thinking here about
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  Speaker 1: a patient with schizophrenia who no longer expresses much emotion
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  Speaker 1: and rarely initiates activity. So negative symptoms, decreased mesocortical dopamine activity.
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  Speaker 1: The nigrostriatal pathway is movement. It helps regulate movement. This
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  Speaker 1: becomes especially important when questions about antipsychotic side effects. Blocking
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  Speaker 1: dopamine in this pathway can produce what they call extrapyramidal
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  Speaker 1: symptoms or EPS. like acute dystonia, akathisia, Parkinsonian symptoms, tardive dyskinesia.
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  Speaker 1: Imagine someone begins an antipsychotic medication, later develops rigidity, tremor,
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  Speaker 1: and slow movement. The pathway immediately come to mind is nigrostriatal,
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  Speaker 1: which equals movement. And for the final one is tuberoinfadibular
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  Speaker 1: pathway prolactin. Finally, this probably helps prolactin secretion. So dopamine
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  Speaker 1: inhibits prolactin release. Therefore, blocking the receptors can cause prolactin
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  Speaker 1: levels to increase. Possible consequences include galacteria, menstrual disturbances, sexual dysfunction,
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  Speaker 1: and gynecomastia. A vignette could look like this. Tuberofendibular pathway,
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  Speaker 1: the EPPP memory trick, reduced the entire topic to four words.
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  Speaker 1: Mesolimbic positive, mesocortical negative, nigrostriatal movement, tuberofendibular prolactin. A patient
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  Speaker 1: with schizophrenia experiences auditory hallucinations and persecutory delusions. You should
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  Speaker 1: be thinking mesolimbic pathway. Positive symptoms, mesolimbic, negative, mesocortical, movement, nigrostriatal, prolactin, tubero,
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  Speaker 1: and fibrillary.