Is there a certain reason behind it? Or does it operate off the principle of trying to balance the neurotransmitter(NT):NeurotransmitterReceptor(NTR) ratio?
For instance, I've read that supplements that boost your Dopamine can cause an upregulation of Dopamine Receptors, and quite possibly an upregulation of dopamine production.
Though, this idea comes into conflict with the basic idea of addiction. Where, if Neurotransmitter levels are too high, receptor density is decreased to balance back to the default psychological state.
Is there some sort of threshold to where upregulation will stop occuring and down regulation will occur based upon the levels of said Neurotransmitter?
For example, I take L-Theanine(GABA precursor - also raises dopamine) and L-Tyrosine(Dopamine Precursor).
L-Theanine is said to cause an upregulation of your GABA system over time, including upregulation of receptor density. L-Tyrosine is said to upregulate Dopamine Receptors and the Dopamine systems.
The only possible way I can see this being possible is... the brain does not increase receptor density(and that specific neurotransmitter system) as a direct result of a hightened level of neurotransmitters.... but rather, what if something in the conversation process of the precursor tells the brain more receptors are needed?
This idea would explain why upregulation of receptors does not happen with drugs that spike certain neurotransmitters(meth, sex, cocaine, heroin)... but would explain why upregulation of a NT System would occur when taking precursors.
What do you guys think? I feel if I better understood the actual causes of Upregulation and Downregulation, I could more easily gauge the long term effects of the precursoral supplements that I take.