What is known about the role of endogenous opioid activity in the body and play behavior in rodent models and/or children (humans).

What is known about the role of endogenous opioid activity in the body and play behavior in rodent models and/or children (humans). So you want to keep any references in which endogenous opioid and play behavior in rodents (i.e., rats/mice/hamsters…) and children

Question 5: