There is an interraction between DOPA and Endorphins.
There are some elements refering to endorphins and some others to dopamine. But both are linked each other and it could be a chronological mechanism including both neurotransmitters.
There is the opinion of doctor Jiang where the Pois symptoms are similar to opiate withdrawal symptoms (flu-like especially, anxiety and loss of concentration).
But some elements make us think to dopamine (muscular, weakness, loss of motivation... and digestive relatioships.)