Dopamine: please explain endogenous and exogenous and some diseases and treatments?
Question by anonymous: Dopamine: please explain endogenous and exogenous and some diseases and treatments?
Dopamine is a neurotransmitter that I really don’t understand as much as other NTs because of its varied implications and medication forms. For example, I have a hard time understanding the reason for its varied implications in many different diseases/conditions, such as the use of L-Dopa for Parkinson’s all the way to use of Da in the IV form for shock. And the implication of Da in cocaine addiction.
I’d appreciate any explanation. The more detailed and technical, the better. Thank you. I’ve never studied biochemistry or any subject like this, just pharmacology and pathophysiology.
One time I was trying to convince a person that cocaine use was harmful and I knew it had something to do with Da receptors, but I wasn’t sure so I didn’t mention anything in physiological detail…
You are a nice doc! Thanks. Even if no one else would bother with this question, your reply is complete and sufficient. Thanks!!!
Best answer:
Answer by nicedoc
Dopamine has a wide variety of functions physiologically. It’s a neurotransmitter heavily involved in control of motor function (in the extrapyramidal system). Diseases that deal with dopamine deficient states like Parkinson’s disease lead to slowness of movement and resting tremor. This can also occur as a side effect of long term of antipsychotics which block dopamine receptors and hence such patients can look like they have Parkinson’s (in fact we call this drug-induced parkinsonism or DIP).
Dopamine also figures prominently in behavior particularly in risk-reward pathway (like the rush one gets when winning a big hand while gambling for example), obsessive-compulsiveness and manic states. Hence drugs of abuse like cocaine and amphetamines have their pleasurable effect by modulating dopaminergic systems (cocaine for example blocks the reuptake of dopamine among other monoamines, thus making dopamine and thus its effects last longer in the nervous system). Likewise, treatments for Parkinson’s disease, particularly dopamine agonists can have compulsive behaviors such as excessive gambling/shopping and obessive-compulsive behavoirs as side effects.
Dopamine also has effects on blood pressure; interestingly at low doses it can lower blood pressure but at higher doses it can increase blood pressure (and is used medically for this reason as a vasopressor). However, as dopamine is broken down very quickly in the peripheral system, it’s unlikely it actually plays a real role in blood pressure control under normal conditions.
When people talk about endogenous vs exogenous dopamine, it just refers to whether the dopamine comes from existing physiologic stores (endogenous) or from an outside source, like a medication (exogenous). Thus you could say cocaine works by enhancing the effects of endogenous dopamine while Sinemet, a Parkinson’s disease drug , works by supplying exogenous dopamine.
Hope this helps somewhat.
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