 A study performed in 1984 by FR Huebner et. al. looked at the binding action of various wheat proteins on the opiate receptors of rats. This study separated out peptides from wheat proteins and tested them for opiate-like activity at competitive binding sites in the rat brain, comparing them with tridium-labeled doses of dihydromorphine. While some peptides showed no activity, those associated with the gliadin fraction of the gluten complex studied demonstrated activity equivalent to 1 nM of morphine in the rat brain, indicating opiate activity.