For the record- I have an incredible tolerance for pain. Never get anesthetic for minor surgeries. Never flinch.
Dopamine D1 and D2 receptor activation results in pain suppression.
A strep antibody which may cause OCD binds to dopamine D1 and D2 receptors in the brain.
My father has Parkinson's and is on dopamine replacement medication- he falls and injures himself quite often and never notices the wounds.