Autoradiographic localization of supraspinal kappa-opioid receptors with [125I-Tyr1, D-Pro10]dynorphin A-(1-11).

[125I-Tyr1, D-Pro10]dynorphin A-(1-11) (125I-DP-DYN), an opioid peptide analogue that has previously been shown to be kappa selective, displays specific, saturable, and high-affinity (Kd = 0.3 nM) binding in slide-mounted sections from nerve tissue. We have used 125I-DPDYN to autoradiographically visualize supraspinal kappa-opioid receptor sites in rats, guinea pigs, and rabbits. The autoradiographic dispositions of 125I-DPDYN in sections from cerebellum are clearly different in guinea pig and rabbit, suggesting that kappa receptors have different functions in this organ of the two species. Autoradiograms from 125I-DPDYN-labeled brain sections also reveal major species differences, in particular in thalamus, which is densely labeled in rabbit and considerably less so in rat and guinea pig. The data show that 125I-DPDYN is a useful probe to visualize kappa-opioid receptor sites in nerve tissue sections directly and rapidly.