Effects of opioids on neuronal survival in culture of embryonic chick dorsal root ganglion neurons

We studied the effects of endogenous and synthetic opioids on survival of primary-cultured dorsal root ganglion neurons of 8-day chick embryos. In the basal growth medium containing nerve growth factor (NGF), [Leu(5)]enkephalin, [Met(5)]enkephalin or selective mu-agonist, [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]enkephalin (DAMGO) produced significant increase of neuronal survival in a naloxone-reversible manner. On the other hand, dynorphin A (1-13), [D-Pen(2), L-Pens] enkephalin (DPLPE) (a delta-agonist) and U-50,488 (a kappa-agonist) showed no such effect. No viable neurons were observed in the absence of NGF in spite of the presence of any opioid peptides. These results suggest that [Leu(5)]enkephalin and [Met(5)]enkephalin might increase neuronal survival by stimulating mu-opioid receptors, and that these opioid peptides are working with other growth factors but, in and by themselves, do not promote survival. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.