Dopamine: For More than Mobility

About half of those dealing with LBD also have Parkinson's disease (PD). Anyone dealing with PD soon learns about the need for adequate dopamine.

Dopamine has several functions in the brain, including:

• Facilitating mobility. This is the function that PlwPD are most aware of. Without adequate dopamine, symptoms such as slowness of movement, tremor and stiffness occur.
• Reward-based behavior. Anything we consider a treat will increase the secretion of dopamine which facilitates positive emotions. Certain drugs also cause an increase of dopamine, which can make them addictive.
• Executive functions. In the cortex of the brain, dopamine and acetylcholine play a delicate balancing act that is seldom a problem until cognition becomes an issue.
• Pain management. In multiple areas of the brain, dopamine acts to decrease pain. Too little dopamine results in more pain, as in restless leg syndrome and an increases susceptibility to pain for PlwPD.

Drug issues. The body protects the brain with a barrier that prevents most substances from passing from the general blood stream into the brain. This is called the blood brain barrier (BBB). Dopamine by itself cannot cross the BBB and so doctors have to find ways around it.

• Levadopa is a precursor of dopamine that can cross the BBB. Once it is inside the brain, it transforms into dopamine. While levadopa works well for mobility, its effect on mood is limited. Thus, depression is a common PD symptom not treated well with levadopa.
• Cognition. When PD advances to PDD, with decreased acetylcholine levels, levadopa further interferes with the acetylcholine-dopamine balance and increases already present cognitive issues like hallucinations and slow thinking.
• Dopamine agonists are drugs that mimic the action of dopamine and can cross the BBB. These drugs appear to have a better effect and may improve depression. However, when dementia is already present, they can increase cognitive dysfunction and compulsive behaviors.

Outside the brain, dopamine has many other functions. It regulates:

• In the cardiovascular system and kidneys, dopamine acts to increase sodium and water retention, increase heart rate and constrict your blood vessels. Inadequate dopamine can cause low blood pressure and sluggish circulation.
• In the pancreas, dopamine's job is to regulate insulin production. Too much insulin triggers the release of dopamine, which may also may find its way into the brain where it functions as a reward. Eating high carbohydrate "comfort food" is an example of eating to produce higher levels of dopamine.
• In the immune system, dopamine retards lymphocyte activity, acting as a brake for when the immune system gets out of control and attacks healthy cells. Inadequate dopamine would result in increased levels of diseases such as arthritis.
• In the GI tract, dopamine again acts as a brake, reducing gastrointestinal motility and protecting intestinal lining. Too much dopamine can cause constipation. Too little might cause diarrhea and sores on the gut lining.

And so the bottom line is that when a person has PD or PDD, any of these other issues may come into play.  (Reference) (Reference)

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* Acronyms:
LBD: Lewy body dementia
PD: Parkinson's disease
PlwD: person living with dementia
DLB: dementia with Lewy bodies
PDD: Parkinson's disease with dementia
PlwD, PD, LBD, PDD, etc: person/people living with dementia
PlwPD, LBD, PDD, etc.: person/people living with PD, LBD, PDD, etc.
MCI: mild cognitive impairment
MCI-LB: the form of MCI that precedes LBD
BPSD: behavioral and psychological symptoms of dementia

For information about Lewy body disorders, read our books:
A Caregivers’ Guide to Lewy Body Dementia
Managing Cognitive Issues in Parkinson's and Lewy Body Dementia

Helen and James Whitworth are not doctors, lawyers or social workers. As informed caregivers, they share the information here for educational purposes only. It should never be used instead of a professional's advice.