I keep reading all these recreational drugs increase dopamine – the ‘feel good’ drug in the brain. So why is just injecting dopamine itself not a thing?

Question

I keep reading all these recreational drugs increase dopamine – the ‘feel good’ drug in the brain. So why is just injecting dopamine itself not a thing?

In: Biology

Answer 1

First of all, dopamine is not a feel good drug.

Dopamine is a neurotransmitter in the brain involved in several function.

1 : It’s involved in motricity, when your get Parkinson disease, your dopaminergic neuron dies and this causes the motor symptoms.

2 : It’s involved in vision : Some neuron in the retina layers respond/secret dopamine.

3 : It’s involved in hormonal control of like prolactine in the tubero-infundibulum pathway (around the hypophyse)

4 : It’s involved in MOTIVATION in the reward/limbic system. MOTIVATION, not pleasure.

The point of dopamine is to associate a pleasing sensation with an action so you can feel motivated to do it again. It’s at the core of what we call “the reward system” and it motivates you to do stuff.

When you’re eating food, it feels good, what feels good is associated with being beneficial to your survival so you have all the interest in the world to repeat that action so you can thrive.

Dopamine acts like a glue between the “feel good feeling” of eating and the action of eating, so you can associate the two together and later on get more motivated to do it.

Drugs hijack this system by inducing a massive dopamine release while the drugs provoke a feel good sensation : The massive dopamine release associate the feel good feeling with the drugs and you start getting more and more motivated to do it again : That’s how addiction begin.

But dopamine is not pleasure. They did an experiment on rats if you remove the dopaminergic neurons in a region called “the ventral tegmental area” which is the core of the reward system, rats will still exxperience pleasure when they drink sweet water (because rats really like sweets) but they will let themselves die of starvation because they will feel absolutely no motivation to reach for food.

And in drug addiction, way before physical withdrawal kicks in, you get an obsessive motivation to get drugs : that’s called craving. It’s not a seeking of pleasure, it’s a seeking to relief a compulsion : You NEED to do it, you are pushed to do it, you cannot do otherwise. But the pleasure is long gone.

Also, dopamine does not cross the blood brain barrier. So dopamine injection wouldn’t work.