Cloning of Delta Opioid Receptors

Cloning of the opioid receptors did not come easy, and there were many false claims along the way. Efforts began in the mid-1980s in the wake of cloning of the opioid peptide precursors. However, it was not till 1992 that the delta receptor was first cloned and provided the critical probes leading to the characterization of the entire family of opioid receptors.