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 p rimary-cultured dorsal root ganglion neurons of 8-day chick embryos. In the basal growth medium containing nerve growth factor (NGF), [Leu(5)]enkephal in, [Met(5)]enkephalin or selective mu-agonist, [D-Ala(2), N-Me-Phe(4), Gly (5)-ol]enkephalin (DAMGO) produced significant increase of neuronal surviva l 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 kapp a-agonist) showed no such effect. No viable neurons were observed in the ab sence of NGF in spite of the presence of any opioid peptides. These results suggest that [Leu(5)]enkephalin and [Met(5)]enkephalin might increase neur onal survival by stimulating mu-opioid receptors, and that these opioid pep tides are working with other growth factors but, in and by themselves, do n ot promote survival. (C) 1999 Elsevier Science Ireland Ltd. All rights rese rved.