Opiates are known to produce various physiological effects. Our understanding of these effects has been greatly increased by the discovery of the opiate receptor and the endogenous opioid peptides. Recent investigation has demonstrated that three distinct receptor subtypes exist; their function is currently being actively investigated.
DeMaria, Jr, MD, Peter
"Interaction of the Opiate and Neuroendocrine Systems,"
Jefferson Journal of Psychiatry: Vol. 3
, Article 9.
Available at: http://jdc.jefferson.edu/jeffjpsychiatry/vol3/iss1/9