Prostaglandins are chemicals produced in and released from virtually all mammalian cells when they are injured: these are the only pain signals that do not originate in the nervous system.
One of these was a compound called 3-isobutyl-1-methylxanthine (IBMX), which bound very well but actually depressed mouse locomotion.
The documentation of these and other epidemics is slight and frequently unreliable.
Even professors who are experts in the field find it difficult to decide which of these to assign to students.