SUMMARY
The term opioid was coined to refer in a generic sense to all drugs, natural and synthetic, with morphin - like actions. Three distinct families of peptides have been identified so far in gastrointestinal (GI) nervous system in mammalian.
These peptides include : dynorphin, Met - enkephalin and leu - enkephalin .
Results from studies about opioid which have been started 15 years ago ...