dihydromorphine and deltakephalin

The characteristics of opiate binding sites in the retina of the chick, rabbit and goldfish have been investigated. In the newly hatched chick retina, 131 fmol/mg of binding sites for [D-Ala2-D-Leu5]-[3H]enkephalin are present; competition studies with the delta selective peptide [D-Thr-Leu5]-enkephalin (DTLET) and the mu selective peptide morphiceptin show that all of the [D-Ala2-D-Leu5]-[3H]-enkephalin binding sites are of the delta subtype. Dihydro[3H]morphine binds poorly to the chick retina; 13.2 fmol/mg of this binding is displaceable by morphiceptin and corresponds to mu binding sites. Benzomorphan sites are defined as sites occupied by [3H]diprenorphine which is displaceable by low concentrations of ethylketocyclozacine but not by high concentrations of D-Ala2-D-Leu5-enkephalin and morphiceptin. At least 88 fmol/mg of benzomorphan sites are present in the chick retina. [3H]diprenorphine binding to the rabbit and fish retina was measured. The rabbit retina bound 60 fmol/mg, and the fish retina 42 fmol/mg of [3H]diprenorphine. These findings are discussed in the light of the studies on the localization and physiological effects of enkephalin in the retina.

Topics: Animals; Benzomorphans; Chickens; Dihydromorphine; Diprenorphine; Endorphins; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Goldfish; Oligopeptides; Rabbits; Receptors, Opioid; Retina; Species Specificity