Welcome to pharmacology by Lecturio. My name is
Dr. PJ Shukle. We are going to be covering
Parkinson's disease and other movement disorders
and the drugs that we use to help control them.
The dopamine hypothesis of how the brain works is
quite interesting. Reduced dopamine levels are seen
in patients with Parkinson's disease. So quite
naturally we as physicians want to increase those levels.
So we give dopamine agonist. We give dopamine
agonist to these patients with Parkinson's disease
to mitigate their symptoms but long term exposure
to these medications results in increasing
schizophrenic type symptoms and mania and psychotic
symptoms. We know also that treatment of schizophrenia
involves reducing dopamine levels. So you can
see that there is a reaction and an interaction
between Parkinson's disease and schizophrenia and
mania. And the Chinese recognized this 2000 years ago
when they recognized that Parkinson's disease type
syndromes and psychotic diseae type syndromes
were a Yin and Yang kind of relationship. Drugs used
to treat psychosis and hyperactivity rely on
reducing the levels of dopamine and dopamine
transmission in the brain. And drugs used to treat
Parkinson's disease and dyskinesias,
rely on increasing those very same levels.
Drugs used to treat Parkinson's disease can include
dopamine precursors like levodopa, dopamine agonists,
MAO inhibitors, and COMT inhibitors. Drugs used to
treat other diseases include diseases like tremor,
Wilson's disease, complex choreas, Huntington's
disease, and Tourette's syndrome. Let's take a look
at the brain. Now we already looked at this very
same diagram when we were looking at our psychotic
medication. So the effects of increasing dopamine
are quite important. In the nigrostriatal tract,
you improve extrapyramidal function and this
causes an improvement in Parkinsonian symptoms.
The same medications in the mesocortical and
mesolimbic tracts cause apathy and lack of emotion,
and hallucination and delusion. In the TI
tract, this will stimulate prolactin release.
And in the fourth pathway, you are effecting the
chemoreceptor trigger zone. That houses the
vomiting center of the brain and causes anorexia,
nausea and vomiting. So these are important
side effects of the medications that
we use to treat Parkinson's disease.