Opioid peptides act as growth factors in neural and non-neural cells and tissues, in addition to serving in neurotransmission/neuromodulation in the nervous system. The Opioid growth factor receptor is an integral membrane protein associated with the nucleus. The conserved region is situated at the N-terminus of the member proteins with a series of imperfect repeats lying immediately to its C-terminus [1].

1: The biology of the opioid growth factor receptor (OGFr). Zagon IS, Verderame MF, McLaughlin PJ; Brain Res Brain Res Rev 2002;38:351-376. PMID:11890982