An opiate receptor in the neurohypophysis of laying hens

An opiate binding component in the membrane fraction of the neurohypophysis of the laying hen showed a high affinity, limited capacity, reversible binding, and binding specificity to [3H]diprenorphine. The binding sites were of a single class. The equilibrium dissociation constant was .30 +/- .03 nM (mean +/- SEM; n = 5) in Scatchard analysis and .31 +/- .02 nM (n = 5) in kinetic analysis. The maximum binding capacity determined by Scatchard analysis was 619 +/- 34 fmol/mg protein (n = 5). The association and dissociation rate constants determined by kinetic analysis were .088 +/- .002 nM-1 min-1 (n = 5) and .027 +/- .001 min-1 (n = 5), respectively. The results suggest that the binding component is regarded as being an opiate receptor.