Answer:
Some longer-term changes begin as adjustments to compensate for drug-induced increases in neurotransmitter signaling intensity. For example, the brain responds to repeated drug-induced massive dopamine surges in part by reducing its complement of dopamine receptors.
Interesting enough, the byproduct of marijuana that actually is stored anywhere in the blood stream is also the main hallucinogenic and pain relief property THC. THC is interesting in that it will store itself in the bodies fat deposits.