Opiate and opioid peptide binding in rat goldfish: further evidence for opiate receptor heterogeneity.

The binding of a series of 3H-labeled mu, kappa, sigma and delta opioid agonists and an antagonist has been examined in rat and goldfish brain membranes. A variety of treatments, including NaCl, N-ethylmaleimide, trypsin and chymotrypsin show dramatic differences both between the two species and between the different 3H-ligands.